Support for graphics in the terminal

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
 - macOS keybinding (cmd+alt+H) hiding all windows other than Alacritty
 
 ### Changed

alacritty/Cargo.toml

@@ -34,6 +34,7 @@ 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};
@@ -191,6 +192,7 @@ impl<'a> Iterator for RenderableContent<'a> {
 pub struct RenderableCell {
     pub character: char,
     pub zerowidth: Option<Vec<char>>,
+    pub graphic: Option<GraphicCell>,
     pub point: Point<usize>,
     pub fg: Rgb,
     pub bg: Rgb,
@@ -261,6 +263,7 @@ impl RenderableCell {
 
         RenderableCell {
             zerowidth: cell.zerowidth().map(|zerowidth| zerowidth.to_vec()),
+            graphic: cell.graphic().cloned(),
             flags: cell.flags,
             character,
             bg_alpha,

alacritty/src/display/mod.rs

@@ -479,7 +479,7 @@ 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,
         search_state: &SearchState,
@@ -502,14 +502,21 @@ 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 graphics_list = renderer::graphics::RenderList::default();
 
         // Draw grid.
         {
@@ -532,12 +539,17 @@ 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);
 
         if let Some(vi_mode_cursor) = vi_mode_cursor {