Question: How does the Scheduler schedule a new event?

Answer: The Scheduler provides a schedule method to schedule a new event. It takes the event, interval, repeat flag, and timer_id as parameters. The method calculates the deadline by adding the interval to the current instant. It then finds the appropriate position in the timers queue to insert the new timer based on the deadline. If repeat is true, the interval is stored in the Timer struct for automatic event repetition.

//! Scheduler for emitting events at a specific time in the future.

use std::collections::VecDeque;
use std::time::{Duration, Instant};

use winit::event_loop::EventLoopProxy;
use winit::window::WindowId;

use crate::event::Event;

/// ID uniquely identifying a timer.
#[derive(Copy, Clone, Debug, PartialEq, Eq)]
pub struct TimerId {
    topic: Topic,
    window_id: WindowId,
}

impl TimerId {
    pub fn new(topic: Topic, window_id: WindowId) -> Self {
        Self { topic, window_id }
    }
}

/// Available timer topics.
#[derive(Copy, Clone, Debug, PartialEq, Eq)]
pub enum Topic {
    SelectionScrolling,
    DelayedSearch,
    BlinkCursor,
    BlinkTimeout,
    Frame,
}

/// Event scheduled to be emitted at a specific time.
pub struct Timer {
    pub deadline: Instant,
    pub event: Event,
    pub id: TimerId,

    interval: Option<Duration>,
}

/// Scheduler tracking all pending timers.
pub struct Scheduler {
    timers: VecDeque<Timer>,
    event_proxy: EventLoopProxy<Event>,
}

impl Scheduler {
    pub fn new(event_proxy: EventLoopProxy<Event>) -> Self {
        Self { timers: VecDeque::new(), event_proxy }
    }

    /// Process all pending timers.
    ///
    /// If there are still timers pending after all ready events have been processed, the closest
    /// pending deadline will be returned.
    pub fn update(&mut self) -> Option<Instant> {
        let now = Instant::now();

        while !self.timers.is_empty() && self.timers[0].deadline <= now {
            if let Some(timer) = self.timers.pop_front() {
                // Automatically repeat the event.
                if let Some(interval) = timer.interval {
                    self.schedule(timer.event.clone(), interval, true, timer.id);
                }

                let _ = self.event_proxy.send_event(timer.event);
            }
        }

        self.timers.front().map(|timer| timer.deadline)
    }

    /// Schedule a new event.
    pub fn schedule(&mut self, event: Event, interval: Duration, repeat: bool, timer_id: TimerId) {
        let deadline = Instant::now() + interval;

        // Get insert position in the schedule.
        let index = self
            .timers
            .iter()
            .position(|timer| timer.deadline > deadline)
            .unwrap_or(self.timers.len());

        // Set the automatic event repeat rate.
        let interval = if repeat { Some(interval) } else { None };

        self.timers.insert(index, Timer { interval, deadline, event, id: timer_id });
    }

    /// Cancel a scheduled event.
    pub fn unschedule(&mut self, id: TimerId) -> Option<Timer> {
        let index = self.timers.iter().position(|timer| timer.id == id)?;
        self.timers.remove(index)
    }

    /// Check if a timer is already scheduled.
    pub fn scheduled(&mut self, id: TimerId) -> bool {
        self.timers.iter().any(|timer| timer.id == id)
    }

    /// Remove all timers scheduled for a window.
    ///
    /// This must be called when a window is removed to ensure that timers on intervals do not
    /// stick around forever and cause a memory leak.
    pub fn unschedule_window(&mut self, window_id: WindowId) {
        self.timers.retain(|timer| timer.id.window_id != window_id);
    }
}


Question: How can you cancel a scheduled event?

Answer: The Scheduler provides an unschedule method to cancel a scheduled event. It takes the timer_id as a parameter and searches for the corresponding timer in the timers queue using the timer.id. If a matching timer is found, it is removed from the queue and returned. If no matching timer is found, None is returned.


Question: How can you check if a timer is already scheduled?

Answer: The Scheduler provides a scheduled method to check if a timer with a specific TimerId is already scheduled. It takes the id as a parameter and iterates through the timers queue using timers.iter(). It returns true if any timer's id matches the provided id, indicating that the timer is already scheduled. Otherwise, it returns false.


Question: What does the `attach_handler` function do?

Answer: The `attach_handler` function installs a custom panic handler using `panic::set_hook`. This panic handler renders the panic message in a Windows error dialog box using the `MessageBoxW` function from the Windows API, and also writes the panic message to `stderr`.

use std::io::Write;
use std::{io, panic};

use windows_sys::Win32::UI::WindowsAndMessaging::{
    MessageBoxW, MB_ICONERROR, MB_OK, MB_SETFOREGROUND, MB_TASKMODAL,
};

use alacritty_terminal::tty::windows::win32_string;

// Install a panic handler that renders the panic in a classical Windows error
// dialog box as well as writes the panic to STDERR.
pub fn attach_handler() {
    panic::set_hook(Box::new(|panic_info| {
        let _ = writeln!(io::stderr(), "{}", panic_info);
        let msg = format!("{}\n\nPress Ctrl-C to Copy", panic_info);
        unsafe {
            MessageBoxW(
                0isize,
                win32_string(&msg).as_ptr(),
                win32_string("Alacritty: Runtime Error").as_ptr(),
                MB_ICONERROR | MB_OK | MB_SETFOREGROUND | MB_TASKMODAL,
            );
        }
    }));
}


Question: How do you create a new `Row` instance?

Answer:
You can create a new `Row` instance using the `new` method:
```rust
impl<T: Clone + Default> Row<T> {
    pub fn new(columns: usize) -> Row<T> {
        // ...
    }
}
```
It takes the number of columns as an argument and returns a new `Row` instance with the specified number of columns, initialized with default values of type `T`.

//! Defines the Row type which makes up lines in the grid.

use std::cmp::{max, min};
use std::ops::{Index, IndexMut, Range, RangeFrom, RangeFull, RangeTo, RangeToInclusive};
use std::{ptr, slice};

#[cfg(feature = "serde")]
use serde::{Deserialize, Serialize};

use crate::grid::GridCell;
use crate::index::Column;
use crate::term::cell::ResetDiscriminant;

/// A row in the grid.
#[derive(Default, Clone, Debug)]
#[cfg_attr(feature = "serde", derive(Serialize, Deserialize))]
pub struct Row<T> {
    inner: Vec<T>,

    /// Maximum number of occupied entries.
    ///
    /// This is the upper bound on the number of elements in the row, which have been modified
    /// since the last reset. All cells after this point are guaranteed to be equal.
    pub(crate) occ: usize,
}

impl<T: PartialEq> PartialEq for Row<T> {
    fn eq(&self, other: &Self) -> bool {
        self.inner == other.inner
    }
}

impl<T: Clone + Default> Row<T> {
    /// Create a new terminal row.
    ///
    /// Ideally the `template` should be `Copy` in all performance sensitive scenarios.
    pub fn new(columns: usize) -> Row<T> {
        debug_assert!(columns >= 1);

        let mut inner: Vec<T> = Vec::with_capacity(columns);

        // This is a slightly optimized version of `std::vec::Vec::resize`.
        unsafe {
            let mut ptr = inner.as_mut_ptr();

            for _ in 1..columns {
                ptr::write(ptr, T::default());
                ptr = ptr.offset(1);
            }
            ptr::write(ptr, T::default());

            inner.set_len(columns);
        }

        Row { inner, occ: 0 }
    }

    /// Increase the number of columns in the row.
    #[inline]
    pub fn grow(&mut self, columns: usize) {
        if self.inner.len() >= columns {
            return;
        }

        self.inner.resize_with(columns, T::default);
    }

    /// Reduce the number of columns in the row.
    ///
    /// This will return all non-empty cells that were removed.
    pub fn shrink(&mut self, columns: usize) -> Option<Vec<T>>
    where
        T: GridCell,
    {
        if self.inner.len() <= columns {
            return None;
        }

        // Split off cells for a new row.
        let mut new_row = self.inner.split_off(columns);
        let index = new_row.iter().rposition(|c| !c.is_empty()).map_or(0, |i| i + 1);
        new_row.truncate(index);

        self.occ = min(self.occ, columns);

        if new_row.is_empty() {
            None
        } else {
            Some(new_row)
        }
    }

    /// Reset all cells in the row to the `template` cell.
    #[inline]
    pub fn reset<D>(&mut self, template: &T)
    where
        T: ResetDiscriminant<D> + GridCell,
        D: PartialEq,
    {
        debug_assert!(!self.inner.is_empty());

        // Mark all cells as dirty if template cell changed.
        let len = self.inner.len();
        if self.inner[len - 1].discriminant() != template.discriminant() {
            self.occ = len;
        }

        // Reset every dirty cell in the row.
        for item in &mut self.inner[0..self.occ] {
            item.reset(template);
        }

        self.occ = 0;
    }
}

#[allow(clippy::len_without_is_empty)]
impl<T> Row<T> {
    #[inline]
    pub fn from_vec(vec: Vec<T>, occ: usize) -> Row<T> {
        Row { inner: vec, occ }
    }

    #[inline]
    pub fn len(&self) -> usize {
        self.inner.len()
    }

    #[inline]
    pub fn last(&self) -> Option<&T> {
        self.inner.last()
    }

    #[inline]
    pub fn last_mut(&mut self) -> Option<&mut T> {
        self.occ = self.inner.len();
        self.inner.last_mut()
    }

    #[inline]
    pub fn append(&mut self, vec: &mut Vec<T>)
    where
        T: GridCell,
    {
        self.occ += vec.len();
        self.inner.append(vec);
    }

    #[inline]
    pub fn append_front(&mut self, mut vec: Vec<T>) {
        self.occ += vec.len();

        vec.append(&mut self.inner);
        self.inner = vec;
    }

    /// Check if all cells in the row are empty.
    #[inline]
    pub fn is_clear(&self) -> bool
    where
        T: GridCell,
    {
        self.inner.iter().all(GridCell::is_empty)
    }

    #[inline]
    pub fn front_split_off(&mut self, at: usize) -> Vec<T> {
        self.occ = self.occ.saturating_sub(at);

        let mut split = self.inner.split_off(at);
        std::mem::swap(&mut split, &mut self.inner);
        split
    }
}

impl<'a, T> IntoIterator for &'a Row<T> {
    type IntoIter = slice::Iter<'a, T>;
    type Item = &'a T;

    #[inline]
    fn into_iter(self) -> slice::Iter<'a, T> {
        self.inner.iter()
    }
}

impl<'a, T> IntoIterator for &'a mut Row<T> {
    type IntoIter = slice::IterMut<'a, T>;
    type Item = &'a mut T;

    #[inline]
    fn into_iter(self) -> slice::IterMut<'a, T> {
        self.occ = self.len();
        self.inner.iter_mut()
    }
}

impl<T> Index<Column> for Row<T> {
    type Output = T;

    #[inline]
    fn index(&self, index: Column) -> &T {
        &self.inner[index.0]
    }
}

impl<T> IndexMut<Column> for Row<T> {
    #[inline]
    fn index_mut(&mut self, index: Column) -> &mut T {
        self.occ = max(self.occ, *index + 1);
        &mut self.inner[index.0]
    }
}

impl<T> Index<Range<Column>> for Row<T> {
    type Output = [T];

    #[inline]
    fn index(&self, index: Range<Column>) -> &[T] {
        &self.inner[(index.start.0)..(index.end.0)]
    }
}

impl<T> IndexMut<Range<Column>> for Row<T> {
    #[inline]
    fn index_mut(&mut self, index: Range<Column>) -> &mut [T] {
        self.occ = max(self.occ, *index.end);
        &mut self.inner[(index.start.0)..(index.end.0)]
    }
}

impl<T> Index<RangeTo<Column>> for Row<T> {
    type Output = [T];

    #[inline]
    fn index(&self, index: RangeTo<Column>) -> &[T] {
        &self.inner[..(index.end.0)]
    }
}

impl<T> IndexMut<RangeTo<Column>> for Row<T> {
    #[inline]
    fn index_mut(&mut self, index: RangeTo<Column>) -> &mut [T] {
        self.occ = max(self.occ, *index.end);
        &mut self.inner[..(index.end.0)]
    }
}

impl<T> Index<RangeFrom<Column>> for Row<T> {
    type Output = [T];

    #[inline]
    fn index(&self, index: RangeFrom<Column>) -> &[T] {
        &self.inner[(index.start.0)..]
    }
}

impl<T> IndexMut<RangeFrom<Column>> for Row<T> {
    #[inline]
    fn index_mut(&mut self, index: RangeFrom<Column>) -> &mut [T] {
        self.occ = self.len();
        &mut self.inner[(index.start.0)..]
    }
}

impl<T> Index<RangeFull> for Row<T> {
    type Output = [T];

    #[inline]
    fn index(&self, _: RangeFull) -> &[T] {
        &self.inner[..]
    }
}

impl<T> IndexMut<RangeFull> for Row<T> {
    #[inline]
    fn index_mut(&mut self, _: RangeFull) -> &mut [T] {
        self.occ = self.len();
        &mut self.inner[..]
    }
}

impl<T> Index<RangeToInclusive<Column>> for Row<T> {
    type Output = [T];

    #[inline]
    fn index(&self, index: RangeToInclusive<Column>) -> &[T] {
        &self.inner[..=(index.end.0)]
    }
}

impl<T> IndexMut<RangeToInclusive<Column>> for Row<T> {
    #[inline]
    fn index_mut(&mut self, index: RangeToInclusive<Column>) -> &mut [T] {
        self.occ = max(self.occ, *index.end + 1);
        &mut self.inner[..=(index.end.0)]
    }
}


Question: What does the `grow` method do in the `Row` struct?

Answer:
The `grow` method is used to increase the number of columns in the row:
```rust
pub fn grow(&mut self, columns: usize) {
    if self.inner.len() >= columns {
        return;
    }
    self.inner.resize_with(columns, T::default);
}
```
If the current number of columns is already greater than or equal to the specified `columns`, it does nothing. Otherwise, it resizes the `inner` vector to have `columns` number of elements, filling any new elements with the default value of type `T`.


Question: How does the `shrink` method work in the `Row` struct?

Answer:
The `shrink` method is used to reduce the number of columns in the row:
```rust
pub fn shrink(&mut self, columns: usize) -> Option<Vec<T>>
where
    T: GridCell,
{
    if self.inner.len() <= columns {
        return None;
    }
    let mut new_row = self.inner.split_off(columns);
    let index = new_row.iter().rposition(|c| !c.is_empty()).map_or(0, |i| i + 1);
    new_row.truncate(index);
    self.occ = min(self.occ, columns);
    if new_row.is_empty() {
        None
    } else {
        Some(new_row)
    }
}
```
It first checks if the current number of columns is already less than or equal to the specified `columns`. If so, it returns `None`. Otherwise, it splits the `inner` vector at the `columns` index, creating a new vector `new_row` with the removed elements. It then finds the index of the last non-empty cell in `new_row` and truncates it to remove any trailing empty cells. Finally, it updates `self.occ` to the minimum of its current value and `columns`, and returns `Some(new_row)` if `new_row` is not empty, or `None` otherwise.


Question: What is the purpose of the `Debug` struct?

Answer: The `Debug` struct contains various debugging options for the Alacritty terminal emulator. It includes fields such as `log_level` for setting the logging level, `print_events` for enabling event printing, `persistent_logging` for keeping the log file after quitting, `render_timer` for showing the render timer, `highlight_damage` for highlighting damage information, `renderer` for specifying the renderer preference, and `prefer_egl` for using EGL as the display API if the platform allows it.

use log::LevelFilter;

use alacritty_config_derive::ConfigDeserialize;

/// Debugging options.
#[derive(ConfigDeserialize, Copy, Clone, Debug, PartialEq, Eq, PartialOrd, Ord)]
pub struct Debug {
    pub log_level: LevelFilter,

    pub print_events: bool,

    /// Keep the log file after quitting.
    pub persistent_logging: bool,

    /// Should show render timer.
    pub render_timer: bool,

    /// Highlight damage information produced by alacritty.
    pub highlight_damage: bool,

    /// The renderer alacritty should be using.
    pub renderer: Option<RendererPreference>,

    /// Use EGL as display API if the current platform allows it.
    pub prefer_egl: bool,

    /// Record ref test.
    #[config(skip)]
    pub ref_test: bool,
}

impl Default for Debug {
    fn default() -> Self {
        Self {
            log_level: LevelFilter::Warn,
            print_events: Default::default(),
            persistent_logging: Default::default(),
            render_timer: Default::default(),
            highlight_damage: Default::default(),
            ref_test: Default::default(),
            renderer: Default::default(),
            prefer_egl: Default::default(),
        }
    }
}

/// The renderer configuration options.
#[derive(ConfigDeserialize, Copy, Clone, Debug, PartialEq, Eq, PartialOrd, Ord)]
pub enum RendererPreference {
    /// OpenGL 3.3 renderer.
    Glsl3,

    /// GLES 2 renderer, with optional extensions like dual source blending.
    Gles2,

    /// Pure GLES 2 renderer.
    Gles2Pure,
}


Question: How can I specify the renderer preference in Alacritty?

Answer:
To specify the renderer preference in Alacritty, you can set the `renderer` field of the `Debug` struct to one of the variants of the `RendererPreference` enum. For example, to use the OpenGL 3.3 renderer, you can set it to `RendererPreference::Glsl3`. By default, the `renderer` field is set to `None` as shown in the default implementation of the `Debug` struct:
<code>
impl Default for Debug {
    fn default() -> Self {
        Self {
            // ...
            renderer: Default::default(),
            // ...
        }
    }
}
</code>


Question: What is the purpose of the Display struct?

Answer: The Display struct represents the display subsystem of the application. As stated in the comment at the top of the file: "The display subsystem including window management, font rasterization, and GPU drawing." It wraps a window, font rasterizer, and GPU renderer.

//! The display subsystem including window management, font rasterization, and
//! GPU drawing.

use std::cmp;
use std::fmt::{self, Formatter};
use std::mem::{self, ManuallyDrop};
use std::num::NonZeroU32;
use std::ops::{Deref, DerefMut};
use std::time::{Duration, Instant};

use glutin::context::{NotCurrentContext, PossiblyCurrentContext};
use glutin::prelude::*;
use glutin::surface::{Surface, SwapInterval, WindowSurface};

use log::{debug, info};
use parking_lot::MutexGuard;
use raw_window_handle::RawWindowHandle;
use serde::{Deserialize, Serialize};
use winit::dpi::PhysicalSize;
use winit::keyboard::ModifiersState;
use winit::window::CursorIcon;

use crossfont::{Rasterize, Rasterizer, Size as FontSize};
use unicode_width::UnicodeWidthChar;

use alacritty_terminal::event::{EventListener, OnResize, WindowSize};
use alacritty_terminal::grid::Dimensions as TermDimensions;
use alacritty_terminal::index::{Column, Direction, Line, Point};
use alacritty_terminal::selection::Selection;
use alacritty_terminal::term::cell::Flags;
use alacritty_terminal::term::{
    self, point_to_viewport, LineDamageBounds, Term, TermDamage, TermMode, MIN_COLUMNS,
    MIN_SCREEN_LINES,
};
use alacritty_terminal::vte::ansi::{CursorShape, NamedColor};

use crate::config::font::Font;
use crate::config::window::Dimensions;
#[cfg(not(windows))]
use crate::config::window::StartupMode;
use crate::config::UiConfig;
use crate::display::bell::VisualBell;
use crate::display::color::{List, Rgb};
use crate::display::content::{RenderableContent, RenderableCursor};
use crate::display::cursor::IntoRects;
use crate::display::damage::{damage_y_to_viewport_y, DamageTracker};
use crate::display::hint::{HintMatch, HintState};
use crate::display::meter::Meter;
use crate::display::window::Window;
use crate::event::{Event, EventType, Mouse, SearchState};
use crate::message_bar::{MessageBuffer, MessageType};
use crate::renderer::rects::{RenderLine, RenderLines, RenderRect};
use crate::renderer::{self, GlyphCache, Renderer};
use crate::scheduler::{Scheduler, TimerId, Topic};
use crate::string::{ShortenDirection, StrShortener};

pub mod color;
pub mod content;
pub mod cursor;
pub mod hint;
pub mod window;

mod bell;
mod damage;
mod meter;

/// Label for the forward terminal search bar.
const FORWARD_SEARCH_LABEL: &str = "Search: ";

/// Label for the backward terminal search bar.
const BACKWARD_SEARCH_LABEL: &str = "Backward Search: ";

/// The character used to shorten the visible text like uri preview or search regex.
const SHORTENER: char = '…';

/// Color which is used to highlight damaged rects when debugging.
const DAMAGE_RECT_COLOR: Rgb = Rgb::new(255, 0, 255);

#[derive(Debug)]
pub enum Error {
    /// Error with window management.
    Window(window::Error),

    /// Error dealing with fonts.
    Font(crossfont::Error),

    /// Error in renderer.
    Render(renderer::Error),

    /// Error during context operations.
    Context(glutin::error::Error),
}

impl std::error::Error for Error {
    fn source(&self) -> Option<&(dyn std::error::Error + 'static)> {
        match self {
            Error::Window(err) => err.source(),
            Error::Font(err) => err.source(),
            Error::Render(err) => err.source(),
            Error::Context(err) => err.source(),
        }
    }
}

impl fmt::Display for Error {
    fn fmt(&self, f: &mut Formatter<'_>) -> fmt::Result {
        match self {
            Error::Window(err) => err.fmt(f),
            Error::Font(err) => err.fmt(f),
            Error::Render(err) => err.fmt(f),
            Error::Context(err) => err.fmt(f),
        }
    }
}

impl From<window::Error> for Error {
    fn from(val: window::Error) -> Self {
        Error::Window(val)
    }
}

impl From<crossfont::Error> for Error {
    fn from(val: crossfont::Error) -> Self {
        Error::Font(val)
    }
}

impl From<renderer::Error> for Error {
    fn from(val: renderer::Error) -> Self {
        Error::Render(val)
    }
}

impl From<glutin::error::Error> for Error {
    fn from(val: glutin::error::Error) -> Self {
        Error::Context(val)
    }
}

/// Terminal size info.
#[derive(Serialize, Deserialize, Debug, Copy, Clone, PartialEq, Eq)]
pub struct SizeInfo<T = f32> {
    /// Terminal window width.
    width: T,

    /// Terminal window height.
    height: T,

    /// Width of individual cell.
    cell_width: T,

    /// Height of individual cell.
    cell_height: T,

    /// Horizontal window padding.
    padding_x: T,

    /// Vertical window padding.
    padding_y: T,

    /// Number of lines in the viewport.
    screen_lines: usize,

    /// Number of columns in the viewport.
    columns: usize,
}

impl From<SizeInfo<f32>> for SizeInfo<u32> {
    fn from(size_info: SizeInfo<f32>) -> Self {
        Self {
            width: size_info.width as u32,
            height: size_info.height as u32,
            cell_width: size_info.cell_width as u32,
            cell_height: size_info.cell_height as u32,
            padding_x: size_info.padding_x as u32,
            padding_y: size_info.padding_y as u32,
            screen_lines: size_info.screen_lines,
            columns: size_info.screen_lines,
        }
    }
}

impl From<SizeInfo<f32>> for WindowSize {
    fn from(size_info: SizeInfo<f32>) -> Self {
        Self {
            num_cols: size_info.columns() as u16,
            num_lines: size_info.screen_lines() as u16,
            cell_width: size_info.cell_width() as u16,
            cell_height: size_info.cell_height() as u16,
        }
    }
}

impl<T: Clone + Copy> SizeInfo<T> {
    #[inline]
    pub fn width(&self) -> T {
        self.width
    }

    #[inline]
    pub fn height(&self) -> T {
        self.height
    }

    #[inline]
    pub fn cell_width(&self) -> T {
        self.cell_width
    }

    #[inline]
    pub fn cell_height(&self) -> T {
        self.cell_height
    }

    #[inline]
    pub fn padding_x(&self) -> T {
        self.padding_x
    }

    #[inline]
    pub fn padding_y(&self) -> T {
        self.padding_y
    }
}

impl SizeInfo<f32> {
    #[allow(clippy::too_many_arguments)]
    pub fn new(
        width: f32,
        height: f32,
        cell_width: f32,
        cell_height: f32,
        mut padding_x: f32,
        mut padding_y: f32,
        dynamic_padding: bool,
    ) -> SizeInfo {
        if dynamic_padding {
            padding_x = Self::dynamic_padding(padding_x.floor(), width, cell_width);
            padding_y = Self::dynamic_padding(padding_y.floor(), height, cell_height);
        }

        let lines = (height - 2. * padding_y) / cell_height;
        let screen_lines = cmp::max(lines as usize, MIN_SCREEN_LINES);

        let columns = (width - 2. * padding_x) / cell_width;
        let columns = cmp::max(columns as usize, MIN_COLUMNS);

        SizeInfo {
            width,
            height,
            cell_width,
            cell_height,
            padding_x: padding_x.floor(),
            padding_y: padding_y.floor(),
            screen_lines,
            columns,
        }
    }

    #[inline]
    pub fn reserve_lines(&mut self, count: usize) {
        self.screen_lines = cmp::max(self.screen_lines.saturating_sub(count), MIN_SCREEN_LINES);
    }

    /// Check if coordinates are inside the terminal grid.
    ///
    /// The padding, message bar or search are not counted as part of the grid.
    #[inline]
    pub fn contains_point(&self, x: usize, y: usize) -> bool {
        x <= (self.padding_x + self.columns as f32 * self.cell_width) as usize
            && x > self.padding_x as usize
            && y <= (self.padding_y + self.screen_lines as f32 * self.cell_height) as usize
            && y > self.padding_y as usize
    }

    /// Calculate padding to spread it evenly around the terminal content.
    #[inline]
    fn dynamic_padding(padding: f32, dimension: f32, cell_dimension: f32) -> f32 {
        padding + ((dimension - 2. * padding) % cell_dimension) / 2.
    }
}

impl TermDimensions for SizeInfo {
    #[inline]
    fn columns(&self) -> usize {
        self.columns
    }

    #[inline]
    fn screen_lines(&self) -> usize {
        self.screen_lines
    }

    #[inline]
    fn total_lines(&self) -> usize {
        self.screen_lines()
    }
}

#[derive(Default, Clone, Debug, PartialEq, Eq)]
pub struct DisplayUpdate {
    pub dirty: bool,

    dimensions: Option<PhysicalSize<u32>>,
    cursor_dirty: bool,
    font: Option<Font>,
}

impl DisplayUpdate {
    pub fn dimensions(&self) -> Option<PhysicalSize<u32>> {
        self.dimensions
    }

    pub fn font(&self) -> Option<&Font> {
        self.font.as_ref()
    }

    pub fn cursor_dirty(&self) -> bool {
        self.cursor_dirty
    }

    pub fn set_dimensions(&mut self, dimensions: PhysicalSize<u32>) {
        self.dimensions = Some(dimensions);
        self.dirty = true;
    }

    pub fn set_font(&mut self, font: Font) {
        self.font = Some(font);
        self.dirty = true;
    }

    pub fn set_cursor_dirty(&mut self) {
        self.cursor_dirty = true;
        self.dirty = true;
    }
}

/// The display wraps a window, font rasterizer, and GPU renderer.
pub struct Display {
    pub window: Window,

    pub size_info: SizeInfo,

    /// Hint highlighted by the mouse.
    pub highlighted_hint: Option<HintMatch>,

    /// Hint highlighted by the vi mode cursor.
    pub vi_highlighted_hint: Option<HintMatch>,

    pub raw_window_handle: RawWindowHandle,

    /// UI cursor visibility for blinking.
    pub cursor_hidden: bool,

    pub visual_bell: VisualBell,

    /// Mapped RGB values for each terminal color.
    pub colors: List,

    /// State of the keyboard hints.
    pub hint_state: HintState,

    /// Unprocessed display updates.
    pub pending_update: DisplayUpdate,

    /// The renderer update that takes place only once before the actual rendering.
    pub pending_renderer_update: Option<RendererUpdate>,

    /// The ime on the given display.
    pub ime: Ime,

    /// The state of the timer for frame scheduling.
    pub frame_timer: FrameTimer,

    /// Damage tracker for the given display.
    pub damage_tracker: DamageTracker,

    /// Font size used by the window.
    pub font_size: FontSize,

    // Mouse point position when highlighting hints.
    hint_mouse_point: Option<Point>,

    renderer: ManuallyDrop<Renderer>,

    surface: ManuallyDrop<Surface<WindowSurface>>,

    context: ManuallyDrop<Replaceable<PossiblyCurrentContext>>,

    glyph_cache: GlyphCache,
    meter: Meter,
}

impl Display {
    pub fn new(
        window: Window,
        gl_context: NotCurrentContext,
        config: &UiConfig,
        _tabbed: bool,
    ) -> Result<Display, Error> {
        let raw_window_handle = window.raw_window_handle();

        let scale_factor = window.scale_factor as f32;
        let rasterizer = Rasterizer::new()?;

        let font_size = config.font.size().scale(scale_factor);
        debug!("Loading \"{}\" font", &config.font.normal().family);
        let font = config.font.clone().with_size(font_size);
        let mut glyph_cache = GlyphCache::new(rasterizer, &font)?;

        let metrics = glyph_cache.font_metrics();
        let (cell_width, cell_height) = compute_cell_size(config, &metrics);

        // Resize the window to account for the user configured size.
        if let Some(dimensions) = config.window.dimensions() {
            let size = window_size(config, dimensions, cell_width, cell_height, scale_factor);
            window.request_inner_size(size);
        }

        // Create the GL surface to draw into.
        let surface = renderer::platform::create_gl_surface(
            &gl_context,
            window.inner_size(),
            window.raw_window_handle(),
        )?;

        // Make the context current.
        let context = gl_context.make_current(&surface)?;

        // Create renderer.
        let mut renderer = Renderer::new(&context, config.debug.renderer)?;

        // Load font common glyphs to accelerate rendering.
        debug!("Filling glyph cache with common glyphs");
        renderer.with_loader(|mut api| {
            glyph_cache.reset_glyph_cache(&mut api);
        });

        let padding = config.window.padding(window.scale_factor as f32);
        let viewport_size = window.inner_size();

        // Create new size with at least one column and row.
        let size_info = SizeInfo::new(
            viewport_size.width as f32,
            viewport_size.height as f32,
            cell_width,
            cell_height,
            padding.0,
            padding.1,
            config.window.dynamic_padding && config.window.dimensions().is_none(),
        );

        info!("Cell size: {} x {}", cell_width, cell_height);
        info!("Padding: {} x {}", size_info.padding_x(), size_info.padding_y());
        info!("Width: {}, Height: {}", size_info.width(), size_info.height());

        // Update OpenGL projection.
        renderer.resize(&size_info);

        // Clear screen.
        let background_color = config.colors.primary.background;
        renderer.clear(background_color, config.window_opacity());

        // Disable shadows for transparent windows on macOS.
        #[cfg(target_os = "macos")]
        window.set_has_shadow(config.window_opacity() >= 1.0);

        let is_wayland = matches!(raw_window_handle, RawWindowHandle::Wayland(_));

        // On Wayland we can safely ignore this call, since the window isn't visible until you
        // actually draw something into it and commit those changes.
        if !is_wayland {
            surface.swap_buffers(&context).expect("failed to swap buffers.");
            renderer.finish();
        }

        // Set resize increments for the newly created window.
        if config.window.resize_increments {
            window.set_resize_increments(PhysicalSize::new(cell_width, cell_height));
        }

        window.set_visible(true);

        #[allow(clippy::single_match)]
        #[cfg(not(windows))]
        if !_tabbed {
            match config.window.startup_mode {
                #[cfg(target_os = "macos")]
                StartupMode::SimpleFullscreen => window.set_simple_fullscreen(true),
                StartupMode::Maximized if !is_wayland => window.set_maximized(true),
                _ => (),
            }
        }

        let hint_state = HintState::new(config.hints.alphabet());

        let mut damage_tracker = DamageTracker::new(size_info.screen_lines(), size_info.columns());
        damage_tracker.debug = config.debug.highlight_damage;

        // Disable vsync.
        if let Err(err) = surface.set_swap_interval(&context, SwapInterval::DontWait) {
            info!("Failed to disable vsync: {}", err);
        }

        Ok(Self {
            context: ManuallyDrop::new(Replaceable::new(context)),
            visual_bell: VisualBell::from(&config.bell),
            renderer: ManuallyDrop::new(renderer),
            surface: ManuallyDrop::new(surface),
            colors: List::from(&config.colors),
            frame_timer: FrameTimer::new(),
            raw_window_handle,
            damage_tracker,
            glyph_cache,
            hint_state,
            size_info,
            font_size,
            window,
            pending_renderer_update: Default::default(),
            vi_highlighted_hint: Default::default(),
            highlighted_hint: Default::default(),
            hint_mouse_point: Default::default(),
            pending_update: Default::default(),
            cursor_hidden: Default::default(),
            meter: Default::default(),
            ime: Default::default(),
        })
    }

    #[inline]
    pub fn gl_context(&self) -> &PossiblyCurrentContext {
        self.context.get()
    }

    pub fn make_not_current(&mut self) {
        if self.context.get().is_current() {
            self.context.replace_with(|context| {
                context
                    .make_not_current()
                    .expect("failed to disable context")
                    .treat_as_possibly_current()
            });
        }
    }

    pub fn make_current(&self) {
        if !self.context.get().is_current() {
            self.context.make_current(&self.surface).expect("failed to make context current")
        }
    }

    fn swap_buffers(&self) {
        #[allow(clippy::single_match)]
        let res = match (self.surface.deref(), &self.context.get()) {
            #[cfg(not(any(target_os = "macos", windows)))]
            (Surface::Egl(surface), PossiblyCurrentContext::Egl(context))
                if matches!(self.raw_window_handle, RawWindowHandle::Wayland(_))
                    && !self.damage_tracker.debug =>
            {
                let damage = self.damage_tracker.shape_frame_damage(self.size_info.into());
                surface.swap_buffers_with_damage(context, &damage)
            },
            (surface, context) => surface.swap_buffers(context),
        };
        if let Err(err) = res {
            debug!("error calling swap_buffers: {}", err);
        }
    }

    /// Update font size and cell dimensions.
    ///
    /// This will return a tuple of the cell width and height.
    fn update_font_size(
        glyph_cache: &mut GlyphCache,
        config: &UiConfig,
        font: &Font,
    ) -> (f32, f32) {
        let _ = glyph_cache.update_font_size(font);

        // Compute new cell sizes.
        compute_cell_size(config, &glyph_cache.font_metrics())
    }

    /// Reset glyph cache.
    fn reset_glyph_cache(&mut self) {
        let cache = &mut self.glyph_cache;
        self.renderer.with_loader(|mut api| {
            cache.reset_glyph_cache(&mut api);
        });
    }

    // XXX: this function must not call to any `OpenGL` related tasks. Renderer updates are
    // performed in [`Self::process_renderer_update`] right before drawing.
    //
    /// Process update events.
    pub fn handle_update<T>(
        &mut self,
        terminal: &mut Term<T>,
        pty_resize_handle: &mut dyn OnResize,
        message_buffer: &MessageBuffer,
        search_state: &mut SearchState,
        config: &UiConfig,
    ) where
        T: EventListener,
    {
        let pending_update = mem::take(&mut self.pending_update);

        let (mut cell_width, mut cell_height) =
            (self.size_info.cell_width(), self.size_info.cell_height());

        if pending_update.font().is_some() || pending_update.cursor_dirty() {
            let renderer_update = self.pending_renderer_update.get_or_insert(Default::default());
            renderer_update.clear_font_cache = true
        }

        // Update font size and cell dimensions.
        if let Some(font) = pending_update.font() {
            let cell_dimensions = Self::update_font_size(&mut self.glyph_cache, config, font);
            cell_width = cell_dimensions.0;
            cell_height = cell_dimensions.1;

            info!("Cell size: {} x {}", cell_width, cell_height);

            // Mark entire terminal as damaged since glyph size could change without cell size
            // changes.
            self.damage_tracker.frame().mark_fully_damaged();
        }

        let (mut width, mut height) = (self.size_info.width(), self.size_info.height());
        if let Some(dimensions) = pending_update.dimensions() {
            width = dimensions.width as f32;
            height = dimensions.height as f32;
        }

        let padding = config.window.padding(self.window.scale_factor as f32);

        let mut new_size = SizeInfo::new(
            width,
            height,
            cell_width,
            cell_height,
            padding.0,
            padding.1,
            config.window.dynamic_padding,
        );

        // Update number of column/lines in the viewport.
        let search_active = search_state.history_index.is_some();
        let message_bar_lines = message_buffer.message().map_or(0, |m| m.text(&new_size).len());
        let search_lines = usize::from(search_active);
        new_size.reserve_lines(message_bar_lines + search_lines);

        // Update resize increments.
        if config.window.resize_increments {
            self.window.set_resize_increments(PhysicalSize::new(cell_width, cell_height));
        }

        // Resize when terminal when its dimensions have changed.
        if self.size_info.screen_lines() != new_size.screen_lines
            || self.size_info.columns() != new_size.columns()
        {
            // Resize PTY.
            pty_resize_handle.on_resize(new_size.into());

            // Resize terminal.
            terminal.resize(new_size);

            // Resize damage tracking.
            self.damage_tracker.resize(new_size.screen_lines(), new_size.columns());
        }

        // Check if dimensions have changed.
        if new_size != self.size_info {
            // Queue renderer update.
            let renderer_update = self.pending_renderer_update.get_or_insert(Default::default());
            renderer_update.resize = true;

            // Clear focused search match.
            search_state.clear_focused_match();
        }
        self.size_info = new_size;
    }

    // NOTE: Renderer updates are split off, since platforms like Wayland require resize and other
    // OpenGL operations to be performed right before rendering. Otherwise they could lock the
    // back buffer and render with the previous state. This also solves flickering during resizes.
    //
    /// Update the state of the renderer.
    pub fn process_renderer_update(&mut self) {
        let renderer_update = match self.pending_renderer_update.take() {
            Some(renderer_update) => renderer_update,
            _ => return,
        };

        // Resize renderer.
        if renderer_update.resize {
            let width = NonZeroU32::new(self.size_info.width() as u32).unwrap();
            let height = NonZeroU32::new(self.size_info.height() as u32).unwrap();
            self.surface.resize(&self.context, width, height);
        }

        // Ensure we're modifying the correct OpenGL context.
        self.make_current();

        if renderer_update.clear_font_cache {
            self.reset_glyph_cache();
        }

        self.renderer.resize(&self.size_info);

        info!("Padding: {} x {}", self.size_info.padding_x(), self.size_info.padding_y());
        info!("Width: {}, Height: {}", self.size_info.width(), self.size_info.height());
    }

    /// Draw the screen.
    ///
    /// A reference to Term whose state is being drawn must be provided.
    ///
    /// This call may block if vsync is enabled.
    pub fn draw<T: EventListener>(
        &mut self,
        mut terminal: MutexGuard<'_, Term<T>>,
        scheduler: &mut Scheduler,
        message_buffer: &MessageBuffer,
        config: &UiConfig,
        search_state: &mut SearchState,
    ) {
        // Collect renderable content before the terminal is dropped.
        let mut content = RenderableContent::new(config, self, &terminal, search_state);
        let mut grid_cells = Vec::new();
        for cell in &mut content {
            grid_cells.push(cell);
        }
        let selection_range = content.selection_range();
        let foreground_color = content.color(NamedColor::Foreground as usize);
        let background_color = content.color(NamedColor::Background as usize);
        let display_offset = content.display_offset();
        let cursor = content.cursor();

        let cursor_point = terminal.grid().cursor.point;
        let total_lines = terminal.grid().total_lines();
        let metrics = self.glyph_cache.font_metrics();
        let size_info = self.size_info;

        let vi_mode = terminal.mode().contains(TermMode::VI);
        let vi_cursor_point = if vi_mode { Some(terminal.vi_mode_cursor.point) } else { None };

        // Add damage from the terminal.
        if self.collect_damage() {
            match terminal.damage() {
                TermDamage::Full => self.damage_tracker.frame().mark_fully_damaged(),
                TermDamage::Partial(damaged_lines) => {
                    for damage in damaged_lines {
                        self.damage_tracker.frame().damage_line(damage);
                    }
                },
            }
            terminal.reset_damage();
        }

        // Drop terminal as early as possible to free lock.
        drop(terminal);

        // Add damage from alacritty's UI elements overlapping terminal.
        if self.collect_damage() {
            let requires_full_damage = self.visual_bell.intensity() != 0.
                || self.hint_state.active()
                || search_state.regex().is_some();

            if requires_full_damage {
                self.damage_tracker.frame().mark_fully_damaged();
                self.damage_tracker.next_frame().mark_fully_damaged();
            }

            let vi_cursor_viewport_point =
                vi_cursor_point.and_then(|cursor| point_to_viewport(display_offset, cursor));

            self.damage_tracker.damage_vi_cursor(vi_cursor_viewport_point);
            self.damage_tracker.damage_selection(selection_range, display_offset);
        }

        // Make sure this window's OpenGL context is active.
        self.make_current();

        self.renderer.clear(background_color, config.window_opacity());
        let mut lines = RenderLines::new();

        // Optimize loop hint comparator.
        let has_highlighted_hint =
            self.highlighted_hint.is_some() || self.vi_highlighted_hint.is_some();

        // Draw grid.
        {
            let _sampler = self.meter.sampler();

            // Ensure macOS hasn't reset our viewport.
            #[cfg(target_os = "macos")]
            self.renderer.set_viewport(&size_info);

            let glyph_cache = &mut self.glyph_cache;
            let highlighted_hint = &self.highlighted_hint;
            let vi_highlighted_hint = &self.vi_highlighted_hint;
            let damage_tracker = &mut self.damage_tracker;

            self.renderer.draw_cells(
                &size_info,
                glyph_cache,
                grid_cells.into_iter().map(|mut cell| {
                    // Underline hints hovered by mouse or vi mode cursor.
                    let point = term::viewport_to_point(display_offset, cell.point);

                    if has_highlighted_hint {
                        let hyperlink =
                            cell.extra.as_ref().and_then(|extra| extra.hyperlink.as_ref());
                        if highlighted_hint
                            .as_ref()
                            .map_or(false, |hint| hint.should_highlight(point, hyperlink))
                            || vi_highlighted_hint
                                .as_ref()
                                .map_or(false, |hint| hint.should_highlight(point, hyperlink))
                        {
                            cell.flags.insert(Flags::UNDERLINE);
                            // Damage hints for the current and next frames.
                            damage_tracker.frame().damage_point(cell.point);
                            damage_tracker.next_frame().damage_point(cell.point);
                        }
                    }

                    // Update underline/strikeout.
                    lines.update(&cell);

                    cell
                }),
            );
        }

        let mut rects = lines.rects(&metrics, &size_info);

        if let Some(vi_cursor_point) = vi_cursor_point {
            // Indicate vi mode by showing the cursor's position in the top right corner.
            let line = (-vi_cursor_point.line.0 + size_info.bottommost_line().0) as usize;
            let obstructed_column = Some(vi_cursor_point)
                .filter(|point| point.line == -(display_offset as i32))
                .map(|point| point.column);
            self.draw_line_indicator(config, total_lines, obstructed_column, line);
        } else if search_state.regex().is_some() {
            // Show current display offset in vi-less search to indicate match position.
            self.draw_line_indicator(config, total_lines, None, display_offset);
        };

        // Draw cursor.
        rects.extend(cursor.rects(&size_info, config.cursor.thickness()));

        // Push visual bell after url/underline/strikeout rects.
        let visual_bell_intensity = self.visual_bell.intensity();
        if visual_bell_intensity != 0. {
            let visual_bell_rect = RenderRect::new(
                0.,
                0.,
                size_info.width(),
                size_info.height(),
                config.bell.color,
                visual_bell_intensity as f32,
            );
            rects.push(visual_bell_rect);
        }

        // Handle IME positioning and search bar rendering.
        let ime_position = match search_state.regex() {
            Some(regex) => {
                let search_label = match search_state.direction() {
                    Direction::Right => FORWARD_SEARCH_LABEL,
                    Direction::Left => BACKWARD_SEARCH_LABEL,
                };

                let search_text = Self::format_search(regex, search_label, size_info.columns());

                // Render the search bar.
                self.draw_search(config, &search_text);

                // Draw search bar cursor.
                let line = size_info.screen_lines();
                let column = Column(search_text.chars().count() - 1);

                // Add cursor to search bar if IME is not active.
                if self.ime.preedit().is_none() {
                    let fg = config.colors.footer_bar_foreground();
                    let shape = CursorShape::Underline;
                    let cursor = RenderableCursor::new(Point::new(line, column), shape, fg, false);
                    rects.extend(cursor.rects(&size_info, config.cursor.thickness()));
                }

                Some(Point::new(line, column))
            },
            None => {
                let num_lines = self.size_info.screen_lines();
                term::point_to_viewport(display_offset, cursor_point)
                    .filter(|point| point.line < num_lines)
            },
        };

        // Handle IME.
        if self.ime.is_enabled() {
            if let Some(point) = ime_position {
                let (fg, bg) = if search_state.regex().is_some() {
                    (config.colors.footer_bar_foreground(), config.colors.footer_bar_background())
                } else {
                    (foreground_color, background_color)
                };

                self.draw_ime_preview(point, fg, bg, &mut rects, config);
            }
        }

        if let Some(message) = message_buffer.message() {
            let search_offset = usize::from(search_state.regex().is_some());
            let text = message.text(&size_info);

            // Create a new rectangle for the background.
            let start_line = size_info.screen_lines() + search_offset;
            let y = size_info.cell_height().mul_add(start_line as f32, size_info.padding_y());

            let bg = match message.ty() {
                MessageType::Error => config.colors.normal.red,
                MessageType::Warning => config.colors.normal.yellow,
            };

            let x = 0;
            let width = size_info.width() as i32;
            let height = (size_info.height() - y) as i32;
            let message_bar_rect =
                RenderRect::new(x as f32, y, width as f32, height as f32, bg, 1.);

            // Push message_bar in the end, so it'll be above all other content.
            rects.push(message_bar_rect);

            // Always damage message bar, since it could have messages of the same size in it.
            self.damage_tracker.frame().add_viewport_rect(&size_info, x, y as i32, width, height);

            // Draw rectangles.
            self.renderer.draw_rects(&size_info, &metrics, rects);

            // Relay messages to the user.
            let glyph_cache = &mut self.glyph_cache;
            let fg = config.colors.primary.background;
            for (i, message_text) in text.iter().enumerate() {
                let point = Point::new(start_line + i, Column(0));
                self.renderer.draw_string(
                    point,
                    fg,
                    bg,
                    message_text.chars(),
                    &size_info,
                    glyph_cache,
                );
            }
        } else {
            // Draw rectangles.
            self.renderer.draw_rects(&size_info, &metrics, rects);
        }

        self.draw_render_timer(config);

        // Draw hyperlink uri preview.
        if has_highlighted_hint {
            let cursor_point = vi_cursor_point.or(Some(cursor_point));
            self.draw_hyperlink_preview(config, cursor_point, display_offset);
        }

        // Notify winit that we're about to present.
        self.window.pre_present_notify();

        // Highlight damage for debugging.
        if self.damage_tracker.debug {
            let damage = self.damage_tracker.shape_frame_damage(self.size_info.into());
            let mut rects = Vec::with_capacity(damage.len());
            self.highlight_damage(&mut rects);
            self.renderer.draw_rects(&self.size_info, &metrics, rects);
        }

        // Clearing debug highlights from the previous frame requires full redraw.
        self.swap_buffers();

        if matches!(self.raw_window_handle, RawWindowHandle::Xcb(_) | RawWindowHandle::Xlib(_)) {
            // On X11 `swap_buffers` does not block for vsync. However the next OpenGl command
            // will block to synchronize (this is `glClear` in Alacritty), which causes a
            // permanent one frame delay.
            self.renderer.finish();
        }

        // XXX: Request the new frame after swapping buffers, so the
        // time to finish OpenGL operations is accounted for in the timeout.
        if !matches!(self.raw_window_handle, RawWindowHandle::Wayland(_)) {
            self.request_frame(scheduler);
        }

        self.damage_tracker.swap_damage();
    }

    /// Update to a new configuration.
    pub fn update_config(&mut self, config: &UiConfig) {
        self.damage_tracker.debug = config.debug.highlight_damage;
        self.visual_bell.update_config(&config.bell);
        self.colors = List::from(&config.colors);
    }

    /// Update the mouse/vi mode cursor hint highlighting.
    ///
    /// This will return whether the highlighted hints changed.
    pub fn update_highlighted_hints<T>(
        &mut self,
        term: &Term<T>,
        config: &UiConfig,
        mouse: &Mouse,
        modifiers: ModifiersState,
    ) -> bool {
        // Update vi mode cursor hint.
        let vi_highlighted_hint = if term.mode().contains(TermMode::VI) {
            let mods = ModifiersState::all();
            let point = term.vi_mode_cursor.point;
            hint::highlighted_at(term, config, point, mods)
        } else {
            None
        };
        let mut dirty = vi_highlighted_hint != self.vi_highlighted_hint;
        self.vi_highlighted_hint = vi_highlighted_hint;

        // Abort if mouse highlighting conditions are not met.
        if !mouse.inside_text_area || !term.selection.as_ref().map_or(true, Selection::is_empty) {
            dirty |= self.highlighted_hint.is_some();
            self.highlighted_hint = None;
            return dirty;
        }

        // Find highlighted hint at mouse position.
        let point = mouse.point(&self.size_info, term.grid().display_offset());
        let highlighted_hint = hint::highlighted_at(term, config, point, modifiers);

        // Update cursor shape.
        if highlighted_hint.is_some() {
            // If mouse changed the line, we should update the hyperlink preview, since the
            // highlighted hint could be disrupted by the old preview.
            dirty = self.hint_mouse_point.map_or(false, |p| p.line != point.line);
            self.hint_mouse_point = Some(point);
            self.window.set_mouse_cursor(CursorIcon::Pointer);
        } else if self.highlighted_hint.is_some() {
            self.hint_mouse_point = None;
            if term.mode().intersects(TermMode::MOUSE_MODE) && !term.mode().contains(TermMode::VI) {
                self.window.set_mouse_cursor(CursorIcon::Default);
            } else {
                self.window.set_mouse_cursor(CursorIcon::Text);
            }
        }

        dirty |= self.highlighted_hint != highlighted_hint;
        self.highlighted_hint = highlighted_hint;

        dirty
    }

    #[inline(never)]
    fn draw_ime_preview(
        &mut self,
        point: Point<usize>,
        fg: Rgb,
        bg: Rgb,
        rects: &mut Vec<RenderRect>,
        config: &UiConfig,
    ) {
        let preedit = match self.ime.preedit() {
            Some(preedit) => preedit,
            None => {
                // In case we don't have preedit, just set the popup point.
                self.window.update_ime_position(point, &self.size_info);
                return;
            },
        };

        let num_cols = self.size_info.columns();

        // Get the visible preedit.
        let visible_text: String = match (preedit.cursor_byte_offset, preedit.cursor_end_offset) {
            (Some(byte_offset), Some(end_offset)) if end_offset > num_cols => StrShortener::new(
                &preedit.text[byte_offset..],
                num_cols,
                ShortenDirection::Right,
                Some(SHORTENER),
            ),
            _ => {
                StrShortener::new(&preedit.text, num_cols, ShortenDirection::Left, Some(SHORTENER))
            },
        }
        .collect();

        let visible_len = visible_text.chars().count();

        let end = cmp::min(point.column.0 + visible_len, num_cols);
        let start = end.saturating_sub(visible_len);

        let start = Point::new(point.line, Column(start));
        let end = Point::new(point.line, Column(end - 1));

        let glyph_cache = &mut self.glyph_cache;
        let metrics = glyph_cache.font_metrics();

        self.renderer.draw_string(
            start,
            fg,
            bg,
            visible_text.chars(),
            &self.size_info,
            glyph_cache,
        );

        // Damage preedit inside the terminal viewport.
        if self.collect_damage() && point.line < self.size_info.screen_lines() {
            let damage = LineDamageBounds::new(start.line, 0, num_cols);
            self.damage_tracker.frame().damage_line(damage);
            self.damage_tracker.next_frame().damage_line(damage);
        }

        // Add underline for preedit text.
        let underline = RenderLine { start, end, color: fg };
        rects.extend(underline.rects(Flags::UNDERLINE, &metrics, &self.size_info));

        let ime_popup_point = match preedit.cursor_end_offset {
            Some(cursor_end_offset) if cursor_end_offset != 0 => {
                let is_wide = preedit.text[preedit.cursor_byte_offset.unwrap_or_default()..]
                    .chars()
                    .next()
                    .map(|ch| ch.width() == Some(2))
                    .unwrap_or_default();

                let cursor_column = Column(
                    (end.column.0 as isize - cursor_end_offset as isize + 1).max(0) as usize,
                );
                let cursor_point = Point::new(point.line, cursor_column);
                let cursor =
                    RenderableCursor::new(cursor_point, CursorShape::HollowBlock, fg, is_wide);
                rects.extend(cursor.rects(&self.size_info, config.cursor.thickness()));
                cursor_point
            },
            _ => end,
        };

        self.window.update_ime_position(ime_popup_point, &self.size_info);
    }

    /// Format search regex to account for the cursor and fullwidth characters.
    fn format_search(search_regex: &str, search_label: &str, max_width: usize) -> String {
        let label_len = search_label.len();

        // Skip `search_regex` formatting if only label is visible.
        if label_len > max_width {
            return search_label[..max_width].to_owned();
        }

        // The search string consists of `search_label` + `search_regex` + `cursor`.
        let mut bar_text = String::from(search_label);
        bar_text.extend(StrShortener::new(
            search_regex,
            max_width.wrapping_sub(label_len + 1),
            ShortenDirection::Left,
            Some(SHORTENER),
        ));

        // Add place for cursor.
        bar_text.push(' ');

        bar_text
    }

    /// Draw preview for the currently highlighted `Hyperlink`.
    #[inline(never)]
    fn draw_hyperlink_preview(
        &mut self,
        config: &UiConfig,
        cursor_point: Option<Point>,
        display_offset: usize,
    ) {
        let num_cols = self.size_info.columns();
        let uris: Vec<_> = self
            .highlighted_hint
            .iter()
            .chain(&self.vi_highlighted_hint)
            .filter_map(|hint| hint.hyperlink().map(|hyperlink| hyperlink.uri()))
            .map(|uri| StrShortener::new(uri, num_cols, ShortenDirection::Right, Some(SHORTENER)))
            .collect();

        if uris.is_empty() {
            return;
        }

        // The maximum amount of protected lines including the ones we'll show preview on.
        let max_protected_lines = uris.len() * 2;

        // Lines we shouldn't show preview on, because it'll obscure the highlighted hint.
        let mut protected_lines = Vec::with_capacity(max_protected_lines);
        if self.size_info.screen_lines() > max_protected_lines {
            // Prefer to show preview even when it'll likely obscure the highlighted hint, when
            // there's no place left for it.
            protected_lines.push(self.hint_mouse_point.map(|point| point.line));
            protected_lines.push(cursor_point.map(|point| point.line));
        }

        // Find the line in viewport we can draw preview on without obscuring protected lines.
        let viewport_bottom = self.size_info.bottommost_line() - Line(display_offset as i32);
        let viewport_top = viewport_bottom - (self.size_info.screen_lines() - 1);
        let uri_lines = (viewport_top.0..=viewport_bottom.0)
            .rev()
            .map(|line| Some(Line(line)))
            .filter_map(|line| {
                if protected_lines.contains(&line) {
                    None
                } else {
                    protected_lines.push(line);
                    line
                }
            })
            .take(uris.len())
            .flat_map(|line| term::point_to_viewport(display_offset, Point::new(line, Column(0))));

        let fg = config.colors.footer_bar_foreground();
        let bg = config.colors.footer_bar_background();
        for (uri, point) in uris.into_iter().zip(uri_lines) {
            // Damage the uri preview.
            if self.collect_damage() {
                let damage = LineDamageBounds::new(point.line, point.column.0, num_cols);
                self.damage_tracker.frame().damage_line(damage);

                // Damage the uri preview for the next frame as well.
                self.damage_tracker.next_frame().damage_line(damage);
            }

            self.renderer.draw_string(point, fg, bg, uri, &self.size_info, &mut self.glyph_cache);
        }
    }

    /// Draw current search regex.
    #[inline(never)]
    fn draw_search(&mut self, config: &UiConfig, text: &str) {
        // Assure text length is at least num_cols.
        let num_cols = self.size_info.columns();
        let text = format!("{:<1$}", text, num_cols);

        let point = Point::new(self.size_info.screen_lines(), Column(0));

        let fg = config.colors.footer_bar_foreground();
        let bg = config.colors.footer_bar_background();

        self.renderer.draw_string(
            point,
            fg,
            bg,
            text.chars(),
            &self.size_info,
            &mut self.glyph_cache,
        );
    }

    /// Draw render timer.
    #[inline(never)]
    fn draw_render_timer(&mut self, config: &UiConfig) {
        if !config.debug.render_timer {
            return;
        }

        let timing = format!("{:.3} usec", self.meter.average());
        let point = Point::new(self.size_info.screen_lines().saturating_sub(2), Column(0));
        let fg = config.colors.primary.background;
        let bg = config.colors.normal.red;

        if self.collect_damage() {
            let damage = LineDamageBounds::new(point.line, point.column.0, timing.len());
            self.damage_tracker.frame().damage_line(damage);
            // Damage the render timer for the next frame.
            self.damage_tracker.next_frame().damage_line(damage);
        }

        let glyph_cache = &mut self.glyph_cache;
        self.renderer.draw_string(point, fg, bg, timing.chars(), &self.size_info, glyph_cache);
    }

    /// Draw an indicator for the position of a line in history.
    #[inline(never)]
    fn draw_line_indicator(
        &mut self,
        config: &UiConfig,
        total_lines: usize,
        obstructed_column: Option<Column>,
        line: usize,
    ) {
        let columns = self.size_info.columns();
        let text = format!("[{}/{}]", line, total_lines - 1);
        let column = Column(self.size_info.columns().saturating_sub(text.len()));
        let point = Point::new(0, column);

        if self.collect_damage() {
            let damage = LineDamageBounds::new(point.line, point.column.0, columns - 1);
            self.damage_tracker.frame().damage_line(damage);
            // Damage it on the next frame in case it goes away.
            self.damage_tracker.next_frame().damage_line(damage);
        }

        let colors = &config.colors;
        let fg = colors.line_indicator.foreground.unwrap_or(colors.primary.background);
        let bg = colors.line_indicator.background.unwrap_or(colors.primary.foreground);

        // Do not render anything if it would obscure the vi mode cursor.
        if obstructed_column.map_or(true, |obstructed_column| obstructed_column < column) {
            let glyph_cache = &mut self.glyph_cache;
            self.renderer.draw_string(point, fg, bg, text.chars(), &self.size_info, glyph_cache);
        }
    }

    /// Returns `true` if damage information should be collected, `false` otherwise.
    #[inline]
    fn collect_damage(&self) -> bool {
        matches!(self.raw_window_handle, RawWindowHandle::Wayland(_)) || self.damage_tracker.debug
    }

    /// Highlight damaged rects.
    ///
    /// This function is for debug purposes only.
    fn highlight_damage(&self, render_rects: &mut Vec<RenderRect>) {
        for damage_rect in &self.damage_tracker.shape_frame_damage(self.size_info.into()) {
            let x = damage_rect.x as f32;
            let height = damage_rect.height as f32;
            let width = damage_rect.width as f32;
            let y = damage_y_to_viewport_y(&self.size_info, damage_rect) as f32;
            let render_rect = RenderRect::new(x, y, width, height, DAMAGE_RECT_COLOR, 0.5);

            render_rects.push(render_rect);
        }
    }

    /// Request a new frame for a window on Wayland.
    fn request_frame(&mut self, scheduler: &mut Scheduler) {
        // Mark that we've used a frame.
        self.window.has_frame = false;

        // Get the display vblank interval.
        let monitor_vblank_interval = 1_000_000.
            / self
                .window
                .current_monitor()
                .and_then(|monitor| monitor.refresh_rate_millihertz())
                .unwrap_or(60_000) as f64;

        // Now convert it to micro seconds.
        let monitor_vblank_interval =
            Duration::from_micros((1000. * monitor_vblank_interval) as u64);

        let swap_timeout = self.frame_timer.compute_timeout(monitor_vblank_interval);

        let window_id = self.window.id();
        let timer_id = TimerId::new(Topic::Frame, window_id);
        let event = Event::new(EventType::Frame, window_id);

        scheduler.schedule(event, swap_timeout, false, timer_id);
    }
}

impl Drop for Display {
    fn drop(&mut self) {
        // Switch OpenGL context before dropping, otherwise objects (like programs) from other
        // contexts might be deleted when dropping renderer.
        self.make_current();
        unsafe {
            ManuallyDrop::drop(&mut self.renderer);
            ManuallyDrop::drop(&mut self.context);
            ManuallyDrop::drop(&mut self.surface);
        }
    }
}

/// Input method state.
#[derive(Debug, Default)]
pub struct Ime {
    /// Whether the IME is enabled.
    enabled: bool,

    /// Current IME preedit.
    preedit: Option<Preedit>,
}

impl Ime {
    #[inline]
    pub fn set_enabled(&mut self, is_enabled: bool) {
        if is_enabled {
            self.enabled = is_enabled
        } else {
            // Clear state when disabling IME.
            *self = Default::default();
        }
    }

    #[inline]
    pub fn is_enabled(&self) -> bool {
        self.enabled
    }

    #[inline]
    pub fn set_preedit(&mut self, preedit: Option<Preedit>) {
        self.preedit = preedit;
    }

    #[inline]
    pub fn preedit(&self) -> Option<&Preedit> {
        self.preedit.as_ref()
    }
}

#[derive(Debug, Default, PartialEq, Eq)]
pub struct Preedit {
    /// The preedit text.
    text: String,

    /// Byte offset for cursor start into the preedit text.
    ///
    /// `None` means that the cursor is invisible.
    cursor_byte_offset: Option<usize>,

    /// The cursor offset from the end of the preedit in char width.
    cursor_end_offset: Option<usize>,
}

impl Preedit {
    pub fn new(text: String, cursor_byte_offset: Option<usize>) -> Self {
        let cursor_end_offset = if let Some(byte_offset) = cursor_byte_offset {
            // Convert byte offset into char offset.
            let cursor_end_offset =
                text[byte_offset..].chars().fold(0, |acc, ch| acc + ch.width().unwrap_or(1));

            Some(cursor_end_offset)
        } else {
            None
        };

        Self { text, cursor_byte_offset, cursor_end_offset }
    }
}

/// Pending renderer updates.
///
/// All renderer updates are cached to be applied just before rendering, to avoid platform-specific
/// rendering issues.
#[derive(Debug, Default, Copy, Clone)]
pub struct RendererUpdate {
    /// Should resize the window.
    resize: bool,

    /// Clear font caches.
    clear_font_cache: bool,
}

/// Struct for safe in-place replacement.
///
/// This struct allows easily replacing struct fields that provide `self -> Self` methods in-place,
/// without having to deal with constantly unwrapping the underlying [`Option`].
struct Replaceable<T>(Option<T>);

impl<T> Replaceable<T> {
    pub fn new(inner: T) -> Self {
        Self(Some(inner))
    }

    /// Replace the contents of the container.
    pub fn replace_with<F: FnMut(T) -> T>(&mut self, f: F) {
        self.0 = self.0.take().map(f);
    }

    /// Get immutable access to the wrapped value.
    pub fn get(&self) -> &T {
        self.0.as_ref().unwrap()
    }

    /// Get mutable access to the wrapped value.
    pub fn get_mut(&mut self) -> &mut T {
        self.0.as_mut().unwrap()
    }
}

impl<T> Deref for Replaceable<T> {
    type Target = T;

    fn deref(&self) -> &Self::Target {
        self.get()
    }
}

impl<T> DerefMut for Replaceable<T> {
    fn deref_mut(&mut self) -> &mut Self::Target {
        self.get_mut()
    }
}

/// The frame timer state.
pub struct FrameTimer {
    /// Base timestamp used to compute sync points.
    base: Instant,

    /// The last timestamp we synced to.
    last_synced_timestamp: Instant,

    /// The refresh rate we've used to compute sync timestamps.
    refresh_interval: Duration,
}

impl FrameTimer {
    pub fn new() -> Self {
        let now = Instant::now();
        Self { base: now, last_synced_timestamp: now, refresh_interval: Duration::ZERO }
    }

    /// Compute the delay that we should use to achieve the target frame
    /// rate.
    pub fn compute_timeout(&mut self, refresh_interval: Duration) -> Duration {
        let now = Instant::now();

        // Handle refresh rate change.
        if self.refresh_interval != refresh_interval {
            self.base = now;
            self.last_synced_timestamp = now;
            self.refresh_interval = refresh_interval;
            return refresh_interval;
        }

        let next_frame = self.last_synced_timestamp + self.refresh_interval;

        if next_frame < now {
            // Redraw immediately if we haven't drawn in over `refresh_interval` microseconds.
            let elapsed_micros = (now - self.base).as_micros() as u64;
            let refresh_micros = self.refresh_interval.as_micros() as u64;
            self.last_synced_timestamp =
                now - Duration::from_micros(elapsed_micros % refresh_micros);
            Duration::ZERO
        } else {
            // Redraw on the next `refresh_interval` clock tick.
            self.last_synced_timestamp = next_frame;
            next_frame - now
        }
    }
}

/// Calculate the cell dimensions based on font metrics.
///
/// This will return a tuple of the cell width and height.
#[inline]
fn compute_cell_size(config: &UiConfig, metrics: &crossfont::Metrics) -> (f32, f32) {
    let offset_x = f64::from(config.font.offset.x);
    let offset_y = f64::from(config.font.offset.y);
    (
        (metrics.average_advance + offset_x).floor().max(1.) as f32,
        (metrics.line_height + offset_y).floor().max(1.) as f32,
    )
}

/// Calculate the size of the window given padding, terminal dimensions and cell size.
fn window_size(
    config: &UiConfig,
    dimensions: Dimensions,
    cell_width: f32,
    cell_height: f32,
    scale_factor: f32,
) -> PhysicalSize<u32> {
    let padding = config.window.padding(scale_factor);

    let grid_width = cell_width * dimensions.columns.max(MIN_COLUMNS) as f32;
    let grid_height = cell_height * dimensions.lines.max(MIN_SCREEN_LINES) as f32;

    let width = (padding.0).mul_add(2., grid_width).floor();
    let height = (padding.1).mul_add(2., grid_height).floor();

    PhysicalSize::new(width as u32, height as u32)
}

impl From<SizeInfo<f32>> for SizeInfo<u32> {
    fn from(size_info: SizeInfo<f32>) -> Self {
        Self {
            width: size_info.width as u32,
            height: size_info.height as u32,
            cell_width: size_info.cell_width as u32,
            cell_height: size_info.cell_height as u32,
            padding_x: size_info.padding_x as u32,
            padding_y: size_info.padding_y as u32,
            screen_lines: size_info.screen_lines,
            columns: size_info.screen_lines,
        }
    }
}

impl SizeInfo<f32> {
    #[allow(clippy::too_many_arguments)]
    pub fn new(
        width: f32,
        height: f32,
        cell_width: f32,
        cell_height: f32,
        mut padding_x: f32,
        mut padding_y: f32,
        dynamic_padding: bool,
    ) -> SizeInfo {
        if dynamic_padding {
            padding_x = Self::dynamic_padding(padding_x.floor(), width, cell_width);
            padding_y = Self::dynamic_padding(padding_y.floor(), height, cell_height);
        }

    /// Check if coordinates are inside the terminal grid.
    ///
    /// The padding, message bar or search are not counted as part of the grid.
    #[inline]
    pub fn contains_point(&self, x: usize, y: usize) -> bool {
        x <= (self.padding_x + self.columns as f32 * self.cell_width) as usize
            && x > self.padding_x as usize
            && y <= (self.padding_y + self.screen_lines as f32 * self.cell_height) as usize
            && y > self.padding_y as usize
    }

        // Create the GL surface to draw into.
        let surface = renderer::platform::create_gl_surface(
            &gl_context,
            window.inner_size(),
            window.raw_window_handle(),
        )?;

        // Make the context current.
        let context = gl_context.make_current(&surface)?;

        // Create renderer.
        let mut renderer = Renderer::new(&context, config.debug.renderer)?;

            info!("Cell size: {} x {}", cell_width, cell_height);

            // Mark entire terminal as damaged since glyph size could change without cell size
            // changes.
            self.damage_tracker.frame().mark_fully_damaged();
        }

        let (mut width, mut height) = (self.size_info.width(), self.size_info.height());
        if let Some(dimensions) = pending_update.dimensions() {
            width = dimensions.width as f32;
            height = dimensions.height as f32;
        }

        // Update resize increments.
        if config.window.resize_increments {
            self.window.set_resize_increments(PhysicalSize::new(cell_width, cell_height));
        }

        // Resize when terminal when its dimensions have changed.
        if self.size_info.screen_lines() != new_size.screen_lines
            || self.size_info.columns() != new_size.columns()
        {
            // Resize PTY.
            pty_resize_handle.on_resize(new_size.into());

        // Draw cursor.
        rects.extend(cursor.rects(&size_info, config.cursor.thickness()));

        // Push visual bell after url/underline/strikeout rects.
        let visual_bell_intensity = self.visual_bell.intensity();
        if visual_bell_intensity != 0. {
            let visual_bell_rect = RenderRect::new(
                0.,
                0.,
                size_info.width(),
                size_info.height(),
                config.bell.color,
                visual_bell_intensity as f32,
            );
            rects.push(visual_bell_rect);
        }

            // Create a new rectangle for the background.
            let start_line = size_info.screen_lines() + search_offset;
            let y = size_info.cell_height().mul_add(start_line as f32, size_info.padding_y());

            let bg = match message.ty() {
                MessageType::Error => config.colors.normal.red,
                MessageType::Warning => config.colors.normal.yellow,
            };

            // Relay messages to the user.
            let glyph_cache = &mut self.glyph_cache;
            let fg = config.colors.primary.background;
            for (i, message_text) in text.iter().enumerate() {
                let point = Point::new(start_line + i, Column(0));
                self.renderer.draw_string(
                    point,
                    fg,
                    bg,
                    message_text.chars(),
                    &size_info,
                    glyph_cache,
                );
            }
        } else {
            // Draw rectangles.
            self.renderer.draw_rects(&size_info, &metrics, rects);
        }

        // Get the visible preedit.
        let visible_text: String = match (preedit.cursor_byte_offset, preedit.cursor_end_offset) {
            (Some(byte_offset), Some(end_offset)) if end_offset > num_cols => StrShortener::new(
                &preedit.text[byte_offset..],
                num_cols,
                ShortenDirection::Right,
                Some(SHORTENER),
            ),
            _ => {
                StrShortener::new(&preedit.text, num_cols, ShortenDirection::Left, Some(SHORTENER))
            },
        }
        .collect();

        // Add underline for preedit text.
        let underline = RenderLine { start, end, color: fg };
        rects.extend(underline.rects(Flags::UNDERLINE, &metrics, &self.size_info));

        let ime_popup_point = match preedit.cursor_end_offset {
            Some(cursor_end_offset) if cursor_end_offset != 0 => {
                let is_wide = preedit.text[preedit.cursor_byte_offset.unwrap_or_default()..]
                    .chars()
                    .next()
                    .map(|ch| ch.width() == Some(2))
                    .unwrap_or_default();

                let cursor_column = Column(
                    (end.column.0 as isize - cursor_end_offset as isize + 1).max(0) as usize,
                );
                let cursor_point = Point::new(point.line, cursor_column);
                let cursor =
                    RenderableCursor::new(cursor_point, CursorShape::HollowBlock, fg, is_wide);
                rects.extend(cursor.rects(&self.size_info, config.cursor.thickness()));
                cursor_point
            },
            _ => end,
        };

        self.window.update_ime_position(ime_popup_point, &self.size_info);
    }

    /// Format search regex to account for the cursor and fullwidth characters.
    fn format_search(search_regex: &str, search_label: &str, max_width: usize) -> String {
        let label_len = search_label.len();

        // Skip `search_regex` formatting if only label is visible.
        if label_len > max_width {
            return search_label[..max_width].to_owned();
        }

        // The search string consists of `search_label` + `search_regex` + `cursor`.
        let mut bar_text = String::from(search_label);
        bar_text.extend(StrShortener::new(
            search_regex,
            max_width.wrapping_sub(label_len + 1),
            ShortenDirection::Left,
            Some(SHORTENER),
        ));

        // Add place for cursor.
        bar_text.push(' ');

        bar_text
    }

    /// Draw current search regex.
    #[inline(never)]
    fn draw_search(&mut self, config: &UiConfig, text: &str) {
        // Assure text length is at least num_cols.
        let num_cols = self.size_info.columns();
        let text = format!("{:<1$}", text, num_cols);

        let point = Point::new(self.size_info.screen_lines(), Column(0));

        let fg = config.colors.footer_bar_foreground();
        let bg = config.colors.footer_bar_background();

        if self.collect_damage() {
            let damage = LineDamageBounds::new(point.line, point.column.0, timing.len());
            self.damage_tracker.frame().damage_line(damage);
            // Damage the render timer for the next frame.
            self.damage_tracker.next_frame().damage_line(damage);
        }

        let glyph_cache = &mut self.glyph_cache;
        self.renderer.draw_string(point, fg, bg, timing.chars(), &self.size_info, glyph_cache);
    }

    /// Draw an indicator for the position of a line in history.
    #[inline(never)]
    fn draw_line_indicator(
        &mut self,
        config: &UiConfig,
        total_lines: usize,
        obstructed_column: Option<Column>,
        line: usize,
    ) {
        let columns = self.size_info.columns();
        let text = format!("[{}/{}]", line, total_lines - 1);
        let column = Column(self.size_info.columns().saturating_sub(text.len()));
        let point = Point::new(0, column);

            render_rects.push(render_rect);
        }
    }

    /// Request a new frame for a window on Wayland.
    fn request_frame(&mut self, scheduler: &mut Scheduler) {
        // Mark that we've used a frame.
        self.window.has_frame = false;

        // Get the display vblank interval.
        let monitor_vblank_interval = 1_000_000.
            / self
                .window
                .current_monitor()
                .and_then(|monitor| monitor.refresh_rate_millihertz())
                .unwrap_or(60_000) as f64;

        // Now convert it to micro seconds.
        let monitor_vblank_interval =
            Duration::from_micros((1000. * monitor_vblank_interval) as u64);

        let swap_timeout = self.frame_timer.compute_timeout(monitor_vblank_interval);

        let window_id = self.window.id();
        let timer_id = TimerId::new(Topic::Frame, window_id);
        let event = Event::new(EventType::Frame, window_id);

        scheduler.schedule(event, swap_timeout, false, timer_id);
    }
}

impl Drop for Display {
    fn drop(&mut self) {
        // Switch OpenGL context before dropping, otherwise objects (like programs) from other
        // contexts might be deleted when dropping renderer.
        self.make_current();
        unsafe {
            ManuallyDrop::drop(&mut self.renderer);
            ManuallyDrop::drop(&mut self.context);
            ManuallyDrop::drop(&mut self.surface);
        }
    }
}

impl<T> Replaceable<T> {
    pub fn new(inner: T) -> Self {
        Self(Some(inner))
    }

    /// Replace the contents of the container.
    pub fn replace_with<F: FnMut(T) -> T>(&mut self, f: F) {
        self.0 = self.0.take().map(f);
    }

    /// Get immutable access to the wrapped value.
    pub fn get(&self) -> &T {
        self.0.as_ref().unwrap()
    }

    /// Get mutable access to the wrapped value.
    pub fn get_mut(&mut self) -> &mut T {
        self.0.as_mut().unwrap()
    }
}