Add Sixel support

Fixes #910

CHANGELOG.md

@@ -16,6 +16,7 @@ The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/).
 - IME composition preview not appearing on Windows
 - Synchronized terminal updates using `DCS = 1 s ST`/`DCS = 2 s ST`
 - Regex terminal hints ([see features.md](./docs/features.md#hints))
+- Support for Sixel protocol
 
 ### Fixed
 

alacritty/Cargo.toml

@@ -35,6 +35,7 @@ libc = "0.2"
 unicode-width = "0.1"
 bitflags = "1"
 dirs = "3.0.1"
+memoffset = "0.6.1"
 
 [build-dependencies]
 gl_generator = "0.14.0"

alacritty/res/graphics.f.glsl

@@ -0,0 +1,40 @@
+#version 330 core
+
+// Index in the textures[] uniform.
+flat in int texId;
+
+// Texture coordinates.
+in vec2 texCoords;
+
+// Array with graphics data.
+uniform sampler2D textures[16];
+
+// Computed color.
+out vec4 color;
+
+void main() {
+ // The expression `textures[texId]` can't be used in OpenGL 3.3.
+ // If we try to use it, the compiler throws this error:
+ //
+ // sampler arrays indexed with non-constant expressions
+ // are forbidden in GLSL 1.30 and later
+ //
+ // To overcome this limitation we use a switch for every valid
+ // value of `texId`.
+ //
+ // The first expression (`textures[texId]`) works with OpenGL 4.0
+ // or later (using `#version 400 core`). If Alacritty drops support
+ // for OpenGL 3.3, this switch block can be replaced with it.
+
+
+#define TEX(N) case N: color = texture(textures[N], texCoords); break;
+
+ switch(texId) {
+ TEX( 0) TEX( 1) TEX( 2) TEX( 3)
+ TEX( 4) TEX( 5) TEX( 6) TEX( 7)
+ TEX( 8) TEX( 9) TEX(10) TEX(11)
+ TEX(12) TEX(13) TEX(14) TEX(15)
+ default:
+ discard;
+ }
+}

alacritty/res/graphics.v.glsl

@@ -0,0 +1,79 @@
+#version 330 core
+
+// ------
+// INPUTS
+
+// Texture associated to the graphic.
+layout(location = 0) in int textureId;
+
+// Sides where the vertex is located.
+//
+// Bit 0 (LSB) is 0 for top and 1 for bottom.
+// Bit 1 is 0 for left and 1 for right.
+layout(location = 1) in int sides;
+
+// Column number in the grid where the left vertex is set.
+layout(location = 2) in float column;
+
+// Line number in the grid where the left vertex is set.
+layout(location = 3) in float line;
+
+// Height in pixels of the texture.
+layout(location = 4) in float height;
+
+// Width in pixels of the texture.
+layout(location = 5) in float width;
+
+// Offset in the X direction.
+layout(location = 6) in float offsetX;
+
+// Offset in the Y direction.
+layout(location = 7) in float offsetY;
+
+// Height in pixels of a single cell when the graphic was added.
+layout(location = 8) in float baseCellHeight;
+
+// -------
+// OUTPUTS
+
+// Texture sent to the fragment shader.
+flat out int texId;
+
+// Coordinates sent to the fragment shader.
+out vec2 texCoords;
+
+// --------
+// UNIFORMS
+
+// Width and height of a single cell.
+uniform vec2 cellDimensions;
+
+// Width and height of the view.
+uniform vec2 viewDimensions;
+
+
+#define IS_RIGHT_SIDE ((sides & 1) == 1)
+#define IS_BOTTOM_SIDE ((sides & 2) == 2)
+
+void main() {
+ float scale = cellDimensions.y / baseCellHeight;
+ float x = (column * cellDimensions.x - offsetX * scale) / (viewDimensions.x / 2) - 1;
+ float y = -(line * cellDimensions.y - offsetY * scale) / (viewDimensions.y / 2) + 1;
+
+ vec4 position = vec4(x, y, 0, 1);
+ vec2 coords = vec2(0, 0);
+
+ if(IS_RIGHT_SIDE) {
+ position.x += scale * width / (viewDimensions.x / 2);
+ coords.x = 1;
+ }
+
+ if(IS_BOTTOM_SIDE) {
+ position.y += -scale * height / (viewDimensions.y / 2);
+ coords.y = 1;
+ }
+
+ gl_Position = position;
+ texCoords = coords;
+ texId = textureId;
+}

alacritty/src/display/content.rs

@@ -6,6 +6,7 @@ use std::ops::{Deref, DerefMut, RangeInclusive};
 use alacritty_terminal::ansi::{Color, CursorShape, NamedColor};
 use alacritty_terminal::config::Config;
 use alacritty_terminal::event::EventListener;
+use alacritty_terminal::graphics::GraphicCell;
 use alacritty_terminal::grid::{Dimensions, Indexed};
 use alacritty_terminal::index::{Column, Direction, Line, Point};
 use alacritty_terminal::term::cell::{Cell, Flags};
@@ -178,6 +179,7 @@ impl<'a> Iterator for RenderableContent<'a> {
 pub struct RenderableCell {
  pub character: char,
  pub zerowidth: Option<Vec<char>>,
+ pub graphic: Option<GraphicCell>,
  pub point: Point,
  pub fg: Rgb,
  pub bg: Rgb,
@@ -240,6 +242,7 @@ impl RenderableCell {
  RenderableCell {
  character,
  zerowidth: cell.zerowidth().map(|zerowidth| zerowidth.to_vec()),
+ graphic: cell.graphic().cloned(),
  point: cell.point,
  fg: fg_rgb,
  bg: bg_rgb,

alacritty/src/display/mod.rs

@@ -470,7 +470,7 @@ impl Display {
  /// This call may block if vsync is enabled.
  pub fn draw<T: EventListener>(
  &mut self,
- terminal: MutexGuard<'_, Term<T>>,
+ mut terminal: MutexGuard<'_, Term<T>>,
  message_buffer: &MessageBuffer,
  config: &Config,
  mouse: &Mouse,
@@ -505,15 +505,22 @@ impl Display {
  let vi_mode = terminal.mode().contains(TermMode::VI);
  let vi_mode_cursor = if vi_mode { Some(terminal.vi_mode_cursor) } else { None };
 
+ let graphics_queues = terminal.graphics_take_queues();
+
  // Drop terminal as early as possible to free lock.
  drop(terminal);
 
  self.renderer.with_api(&config.ui_config, &size_info, |api| {
  api.clear(background_color);
  });
 
+ if let Some(graphics_queues) = graphics_queues {
+ self.renderer.graphics_run_updates(graphics_queues, &size_info);
+ }
+
  let mut lines = RenderLines::new();
  let mut urls = Urls::new();
+ let mut graphics_list = renderer::graphics::RenderList::default();
 
  // Draw grid.
  {
@@ -542,12 +549,17 @@ impl Display {
  // Update underline/strikeout.
  lines.update(&cell);
 
+ // Track any graphic present in the cell.
+ graphics_list.update(&cell);
+
  // Draw the cell.
  api.render_cell(cell, glyph_cache);
  }
  });
  }
 
+ self.renderer.graphics_draw(graphics_list, &size_info);
+
  let mut rects = lines.rects(&metrics, &size_info);
 
  // Update visible URLs.