Add Sixel support

Fixes #910

10 files changed, 1021 insertions, 1 deletions

diff --git a/alacritty/Cargo.toml b/alacritty/Cargo.toml
index 6984728a..cb269350 100644
--- a/alacritty/Cargo.toml
+++ b/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"
diff --git a/alacritty/res/graphics.f.glsl b/alacritty/res/graphics.f.glsl
new file mode 100644
index 00000000..28da2a68
--- /dev/null
+++ b/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;
+    }
+}
diff --git a/alacritty/res/graphics.v.glsl b/alacritty/res/graphics.v.glsl
new file mode 100644
index 00000000..56998e9d
--- /dev/null
+++ b/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;
+}
diff --git a/alacritty/src/display/content.rs b/alacritty/src/display/content.rs
index 2deb3d3e..85719c06 100644
--- a/alacritty/src/display/content.rs
+++ b/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};
@@ -187,6 +188,7 @@ pub struct RenderableCell {
     pub character: char,
     pub zerowidth: Option<Vec<char>>,
     pub point: Point<usize>,
+    pub graphic: Option<GraphicCell>,
     pub fg: Rgb,
     pub bg: Rgb,
     pub bg_alpha: f32,
@@ -257,6 +259,7 @@ impl RenderableCell {
 
         RenderableCell {
             zerowidth: cell.zerowidth().map(|zerowidth| zerowidth.to_vec()),
+            graphic: cell.graphic().cloned(),
             flags: cell.flags,
             character,
             bg_alpha,
diff --git a/alacritty/src/display/mod.rs b/alacritty/src/display/mod.rs
index d4c5c274..5e958f03 100644
--- a/alacritty/src/display/mod.rs
+++ b/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,
@@ -502,6 +502,8 @@ 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);
 
@@ -509,7 +511,12 @@ impl Display {
             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 {
diff --git a/alacritty/src/renderer/graphics/draw.rs b/alacritty/src/renderer/graphics/draw.rs
new file mode 100644
index 00000000..81013b85
--- /dev/null
+++ b/alacritty/src/renderer/graphics/draw.rs
@@ -0,0 +1,242 @@
+//! This module implements the functionality to render graphic textures
+//! in the display.
+//!
+//! [`RenderList`] is used to track graphics in the visible cells. When all
+//! cells in the grid are read, graphics are rendered using the positions
+//! found in those cells.
+
+use std::collections::BTreeMap;
+use std::mem::{self, MaybeUninit};
+
+use crate::display::content::RenderableCell;
+use crate::gl::{self, types::*};
+use crate::renderer::graphics::{shader, GraphicsRenderer};
+
+use alacritty_terminal::graphics::GraphicId;
+use alacritty_terminal::index::{Column, Line};
+use alacritty_terminal::term::SizeInfo;
+
+use log::trace;
+
+/// Position to render each texture in the grid.
+struct RenderPosition {
+    column: Column,
+    line: Line,
+    offset_x: u16,
+    offset_y: u16,
+}
+
+/// Track textures to be rendered in the display.
+#[derive(Default)]
+pub struct RenderList {
+    items: BTreeMap<GraphicId, RenderPosition>,
+}
+
+impl RenderList {
+    /// Detects if the cell contains a graphic, then add it to the render list.
+    ///
+    /// The graphic is added only the first time it is found in a cell.
+    #[inline]
+    pub fn update(&mut self, cell: &RenderableCell) {
+        if let Some(graphic) = &cell.graphic {
+            let graphic_id = graphic.graphic_id();
+            if self.items.contains_key(&graphic_id) {
+                return;
+            }
+
+            let render_item = RenderPosition {
+                column: cell.point.column,
+                line: cell.point.line,
+                offset_x: graphic.offset_x,
+                offset_y: graphic.offset_y,
+            };
+
+            self.items.insert(graphic_id, render_item);
+        }
+    }
+
+    /// Returns `true` if there are no items to render.
+    #[inline]
+    pub fn is_empty(&self) -> bool {
+        self.items.is_empty()
+    }
+
+    /// Builds a list of vertex for the shader program.
+    pub fn build_vertices(self, renderer: &GraphicsRenderer) -> Vec<shader::Vertex> {
+        use shader::VertexSide::{BottomLeft, BottomRight, TopLeft, TopRight};
+
+        let mut vertices = Vec::new();
+
+        for (graphics_id, render_item) in self.items {
+            let graphic_texture = match renderer.graphic_textures.get(&graphics_id) {
+                Some(tex) => tex,
+                None => continue,
+            };
+
+            vertices.reserve(6);
+
+            let vertex = shader::Vertex {
+                texture_id: graphic_texture.texture.0,
+                sides: TopLeft,
+                column: render_item.column.0 as GLuint,
+                line: render_item.line.0 as GLuint,
+                height: graphic_texture.height,
+                width: graphic_texture.width,
+                offset_x: render_item.offset_x,
+                offset_y: render_item.offset_y,
+                base_cell_height: graphic_texture.cell_height,
+            };
+
+            vertices.push(vertex);
+
+            for &sides in &[TopRight, BottomLeft, TopRight, BottomRight, BottomLeft] {
+                vertices.push(shader::Vertex { sides, ..vertex });
+            }
+        }
+
+        vertices
+    }
+
+    /// Draw graphics in the display, using the graphics rendering shader
+    /// program.
+    pub fn draw(self, renderer: &GraphicsRenderer, size_info: &SizeInfo) {
+        let vertices = self.build_vertices(renderer);
+
+        // Initialize the rendering program.
+        unsafe {
+            gl::BindBuffer(gl::ARRAY_BUFFER, renderer.program.vbo);
+            gl::BindVertexArray(renderer.program.vao);
+
+            gl::UseProgram(renderer.program.id);
+
+            gl::Uniform2f(
+                renderer.program.u_cell_dimensions,
+                size_info.cell_width(),
+                size_info.cell_height(),
+            );
+            gl::Uniform2f(
+                renderer.program.u_view_dimensions,
+                size_info.width(),
+                size_info.height(),
+            );
+
+            gl::BlendFuncSeparate(gl::SRC_ALPHA, gl::ONE_MINUS_SRC_ALPHA, gl::SRC_ALPHA, gl::ONE);
+        }
+
+        // Array for storing the batch to render multiple graphics in a single call to the
+        // shader program.
+        //
+        // Each graphic requires 6 vertices (2 triangles to make a rectangle), and we will
+        // never have more than `TEXTURES_ARRAY_SIZE` graphics in a single call, so we set
+        // the array size to the maximum value that we can use.
+        let mut batch = [MaybeUninit::uninit(); shader::TEXTURES_ARRAY_SIZE * 6];
+        let mut batch_size = 0;
+
+        macro_rules! send_batch {
+            () => {
+                #[allow(unused_assignments)]
+                if batch_size > 0 {
+                    trace!("Call glDrawArrays with {} items", batch_size);
+
+                    unsafe {
+                        gl::BufferData(
+                            gl::ARRAY_BUFFER,
+                            (batch_size * mem::size_of::<shader::Vertex>()) as isize,
+                            batch.as_ptr().cast(),
+                            gl::STREAM_DRAW,
+                        );
+
+                        gl::DrawArrays(gl::TRIANGLES, 0, batch_size as GLint);
+                    }
+
+                    batch_size = 0;
+                }
+            };
+        }
+
+        // In order to send textures to the shader program we need to get a _slot_
+        // for every texture associated to a graphic.
+        //
+        // We have `u_textures.len()` slots available in each execution of the
+        // shader.
+        //
+        // For each slot we need three values:
+        //
+        // - The texture unit for `glActiveTexture` (`GL_TEXTUREi`).
+        // - The uniform location for `textures[i]`.
+        // - The index `i`, used to set the value of the uniform.
+        //
+        // These values are generated using the `tex_slots_generator` iterator.
+        //
+        // A single graphic has 6 vertices. All vertices will use the same texture
+        // slot. To detect if a texture has already a slot, we only need to compare
+        // with the last texture (`last_tex_slot`) because all the vertices of a
+        // single graphic are consecutive.
+        //
+        // When all slots are occupied, or the batch array is full, the current
+        // batch is sent and the iterator is reset.
+        //
+        // This logic could be simplified using the [Bindless Texture extension],
+        // but it is not a core feature of any OpenGL version, so hardware support
+        // is uncertain.
+        //
+        // [Bindless Texture extension]: https://www.khronos.org/opengl/wiki/Bindless_Texture
+
+        let tex_slots_generator = (gl::TEXTURE0..=gl::TEXTURE31)
+            .zip(renderer.program.u_textures.iter())
+            .zip(0_u32..)
+            .map(|((tex_enum, &u_texture), index)| (tex_enum, u_texture, index));
+
+        let mut tex_slots = tex_slots_generator.clone();
+
+        // Keep the last allocated slot in a `(texture id, index)` tuple.
+        let mut last_tex_slot = (0, 0);
+
+        for mut vertex in vertices {
+            // Check if we can reuse the last texture slot.
+            if last_tex_slot.0 != vertex.texture_id {
+                last_tex_slot = loop {
+                    match tex_slots.next() {
+                        None => {
+                            // No more slots. Send the batch and reset the iterator.
+                            send_batch!();
+                            tex_slots = tex_slots_generator.clone();
+                        },
+
+                        Some((tex_enum, u_texture, index)) => {
+                            unsafe {
+                                gl::ActiveTexture(tex_enum);
+                                gl::BindTexture(gl::TEXTURE_2D, vertex.texture_id);
+                                gl::Uniform1i(u_texture, index as GLint);
+                            }
+
+                            break (vertex.texture_id, index);
+                        },
+                    }
+                };
+            }
+
+            vertex.texture_id = last_tex_slot.1;
+            batch[batch_size] = MaybeUninit::new(vertex);
+            batch_size += 1;
+
+            if batch_size == batch.len() {
+                send_batch!();
+            }
+        }
+
+        send_batch!();
+
+        // Reset state.
+        unsafe {
+            gl::BlendFunc(gl::SRC1_COLOR, gl::ONE_MINUS_SRC1_COLOR);
+
+            gl::ActiveTexture(gl::TEXTURE0);
+            gl::BindTexture(gl::TEXTURE_2D, 0);
+
+            gl::UseProgram(0);
+            gl::BindVertexArray(0);
+            gl::BindBuffer(gl::ARRAY_BUFFER, 0);
+        }
+    }
+}
diff --git a/alacritty/src/renderer/graphics/mod.rs b/alacritty/src/renderer/graphics/mod.rs
new file mode 100644
index 00000000..3fecd549
--- /dev/null
+++ b/alacritty/src/renderer/graphics/mod.rs
@@ -0,0 +1,149 @@
+//! This module implements the functionality to support graphics in the grid.
+
+use std::mem;
+
+use alacritty_terminal::graphics::{ColorType, GraphicData, GraphicId, UpdateQueues};
+use alacritty_terminal::term::SizeInfo;
+
+use log::trace;
+use serde::{Deserialize, Serialize};
+
+use crate::gl;
+use crate::gl::types::*;
+use crate::renderer;
+
+use std::collections::HashMap;
+
+mod draw;
+mod shader;
+
+pub use draw::RenderList;
+
+/// Type for texture names generated in the GPU.
+#[derive(Serialize, Deserialize, Eq, PartialEq, Clone, Debug)]
+pub struct TextureName(GLuint);
+
+// In debug mode, check if the inner value was set to zero, so we can detect if
+// the associated texture was deleted from the GPU.
+#[cfg(debug_assertions)]
+impl Drop for TextureName {
+    fn drop(&mut self) {
+        if self.0 != 0 {
+            log::error!("Texture {} was not deleted.", self.0);
+        }
+    }
+}
+
+/// Texture for a graphic in the grid.
+#[derive(Serialize, Deserialize, PartialEq, Clone, Debug)]
+pub struct GraphicTexture {
+    /// Texture in the GPU where the graphic pixels are stored.
+    texture: TextureName,
+
+    /// Cell height at the moment graphic was created.
+    ///
+    /// Used to scale it if the user increases or decreases the font size.
+    cell_height: f32,
+
+    /// Width in pixels of the graphic.
+    width: u16,
+
+    /// Height in pixels of the graphic.
+    height: u16,
+}
+
+#[derive(Debug)]
+pub struct GraphicsRenderer {
+    /// Program in the GPU to render graphics.
+    program: shader::GraphicsShaderProgram,
+
+    /// Collection to associate graphic identifiers with their textures.
+    graphic_textures: HashMap<GraphicId, GraphicTexture>,
+}
+
+impl GraphicsRenderer {
+    pub fn new() -> Result<GraphicsRenderer, renderer::Error> {
+        let program = shader::GraphicsShaderProgram::new()?;
+        Ok(GraphicsRenderer { program, graphic_textures: HashMap::default() })
+    }
+
+    /// Run the required actions to apply changes for the graphics in the grid.
+    #[inline]
+    pub fn run_updates(&mut self, update_queues: UpdateQueues, size_info: &SizeInfo) {
+        self.remove_graphics(update_queues.remove_queue);
+        self.upload_pending_graphics(update_queues.pending, size_info);
+    }
+
+    /// Release resources used by removed graphics.
+    fn remove_graphics(&mut self, removed_ids: Vec<GraphicId>) {
+        let mut textures = Vec::with_capacity(removed_ids.len());
+        for id in removed_ids {
+            if let Some(mut graphic_texture) = self.graphic_textures.remove(&id) {
+                // Reset the inner value of TextureName, so the Drop implementation
+                // (in debug mode) can verify that the texture was deleted.
+                textures.push(mem::take(&mut graphic_texture.texture.0));
+            }
+        }
+
+        trace!("Call glDeleteTextures with {} items", textures.len());
+
+        unsafe {
+            gl::DeleteTextures(textures.len() as GLint, textures.as_ptr());
+        }
+    }
+
+    /// Create new textures in the GPU, and upload the pixels to them.
+    fn upload_pending_graphics(&mut self, graphics: Vec<GraphicData>, size_info: &SizeInfo) {
+        for graphic in graphics {
+            let mut texture = 0;
+
+            unsafe {
+                gl::GenTextures(1, &mut texture);
+                trace!("Texture generated: {}", texture);
+
+                gl::BindTexture(gl::TEXTURE_2D, texture);
+                gl::TexParameteri(gl::TEXTURE_2D, gl::TEXTURE_MAX_LEVEL, 0);
+                gl::TexParameteri(gl::TEXTURE_2D, gl::TEXTURE_WRAP_S, gl::CLAMP_TO_EDGE as GLint);
+                gl::TexParameteri(gl::TEXTURE_2D, gl::TEXTURE_WRAP_T, gl::CLAMP_TO_EDGE as GLint);
+                gl::TexParameteri(gl::TEXTURE_2D, gl::TEXTURE_MIN_FILTER, gl::LINEAR as GLint);
+                gl::TexParameteri(gl::TEXTURE_2D, gl::TEXTURE_MAG_FILTER, gl::LINEAR as GLint);
+
+                let pixel_format = match graphic.color_type {
+                    ColorType::Rgb => gl::RGB,
+                    ColorType::Rgba => gl::RGBA,
+                };
+
+                gl::TexImage2D(
+                    gl::TEXTURE_2D,
+                    0,
+                    gl::RGBA as GLint,
+                    graphic.width as GLint,
+                    graphic.height as GLint,
+                    0,
+                    pixel_format,
+                    gl::UNSIGNED_BYTE,
+                    graphic.pixels.as_ptr().cast(),
+                );
+
+                gl::BindTexture(gl::TEXTURE_2D, 0);
+            }
+
+            let graphic_texture = GraphicTexture {
+                texture: TextureName(texture),
+                cell_height: size_info.cell_height(),
+                width: graphic.width as u16,
+                height: graphic.height as u16,
+            };
+
+            self.graphic_textures.insert(graphic.id, graphic_texture);
+        }
+    }
+
+    /// Draw graphics in the display.
+    #[inline]
+    pub fn draw(&mut self, render_list: RenderList, size_info: &SizeInfo) {
+        if !render_list.is_empty() {
+            render_list.draw(self, size_info);
+        }
+    }
+}
diff --git a/alacritty/src/renderer/graphics/shader.rs b/alacritty/src/renderer/graphics/shader.rs
new file mode 100644
index 00000000..8d30d2a3
--- /dev/null
+++ b/alacritty/src/renderer/graphics/shader.rs
@@ -0,0 +1,199 @@
+use std::mem;
+
+use crate::gl;
+use crate::gl::types::*;
+use crate::renderer;
+
+/// Number of elements of the `textures[]` uniform.
+///
+/// If the file `graphics.f.glsl` is modified, this value has to be updated.
+pub(super) const TEXTURES_ARRAY_SIZE: usize = 16;
+
+/// 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.
+#[derive(Debug, Copy, Clone, PartialEq)]
+#[repr(u8)]
+pub enum VertexSide {
+    TopLeft = 0b00,
+    TopRight = 0b10,
+    BottomLeft = 0b01,
+    BottomRight = 0b11,
+}
+
+/// Vertex data to execute the graphics rendering program.
+#[derive(Debug, Copy, Clone, PartialEq)]
+pub struct Vertex {
+    /// Texture associated to the graphic.
+    pub texture_id: GLuint,
+
+    /// Sides where the vertex is located.
+    pub sides: VertexSide,
+
+    /// Column number in the grid where the left vertex is set.
+    pub column: GLuint,
+
+    /// Line where the top vertex is set.
+    pub line: GLuint,
+
+    /// Height, in pixels, of the texture.
+    pub height: u16,
+
+    /// Width, in pixels, of the texture.
+    pub width: u16,
+
+    /// Offset in the x direction.
+    pub offset_x: u16,
+
+    /// Offset in the y direction.
+    pub offset_y: u16,
+
+    /// Height, in pixels, of a single cell when the graphic was added.
+    pub base_cell_height: f32,
+}
+
+/// Sources for the graphics rendering program.
+static GRAPHICS_SHADER_F: &str = include_str!("../../../res/graphics.f.glsl");
+static GRAPHICS_SHADER_V: &str = include_str!("../../../res/graphics.v.glsl");
+
+/// Graphics rendering program.
+#[derive(Debug)]
+pub struct GraphicsShaderProgram {
+    /// Program id.
+    pub id: GLuint,
+
+    /// Uniform of the cell dimensions.
+    pub u_cell_dimensions: GLint,
+
+    /// Uniform of the view dimensions.
+    pub u_view_dimensions: GLint,
+
+    /// Uniform array of the textures.
+    pub u_textures: Vec<GLint>,
+
+    /// Vertex Array Object (VAO) for the fields of `Vertex`.
+    pub vao: GLuint,
+
+    /// Vertex Buffer Object (VBO) to send instances of `Vertex`.
+    pub vbo: GLuint,
+}
+
+impl GraphicsShaderProgram {
+    pub fn new() -> Result<Self, renderer::ShaderCreationError> {
+        let vertex_shader = renderer::create_shader(gl::VERTEX_SHADER, GRAPHICS_SHADER_V)?;
+        let fragment_shader = renderer::create_shader(gl::FRAGMENT_SHADER, GRAPHICS_SHADER_F)?;
+        let program = renderer::create_program(vertex_shader, fragment_shader)?;
+
+        let u_cell_dimensions;
+        let u_view_dimensions;
+        let u_textures;
+
+        unsafe {
+            gl::DeleteShader(fragment_shader);
+            gl::DeleteShader(vertex_shader);
+
+            gl::UseProgram(program);
+
+            // Uniform locations.
+
+            macro_rules! uniform {
+                ($name:literal) => {
+                    gl::GetUniformLocation(
+                        program,
+                        concat!($name, "\0").as_bytes().as_ptr().cast(),
+                    )
+                };
+
+                ($fmt:literal, $($arg:tt)+) => {
+                    match format!(concat!($fmt, "\0"), $($arg)+) {
+                        name => gl::GetUniformLocation(
+                            program,
+                            name.as_bytes().as_ptr().cast(),
+                        )
+                    }
+                };
+            }
+
+            u_cell_dimensions = uniform!("cellDimensions");
+            u_view_dimensions = uniform!("viewDimensions");
+            u_textures =
+                (0..TEXTURES_ARRAY_SIZE).map(|unit| uniform!("textures[{}]", unit)).collect();
+
+            gl::UseProgram(0);
+        }
+
+        let (vao, vbo) = define_vertex_attributes();
+
+        let shader =
+            Self { id: program, u_cell_dimensions, u_view_dimensions, u_textures, vao, vbo };
+
+        Ok(shader)
+    }
+}
+
+/// Build a Vertex Array Object (VAO) and a Vertex Buffer Object (VBO) for
+/// instances of the `Vertex` type.
+fn define_vertex_attributes() -> (GLuint, GLuint) {
+    let mut vao = 0;
+    let mut vbo = 0;
+
+    unsafe {
+        gl::GenVertexArrays(1, &mut vao);
+        gl::GenBuffers(1, &mut vbo);
+
+        gl::BindVertexArray(vao);
+        gl::BindBuffer(gl::ARRAY_BUFFER, vbo);
+
+        let mut attr_index = 0;
+
+        macro_rules! int_attr {
+            ($type:ident, $field:ident) => {
+                gl::VertexAttribIPointer(
+                    attr_index,
+                    1,
+                    gl::$type,
+                    mem::size_of::<Vertex>() as i32,
+                    memoffset::offset_of!(Vertex, $field) as *const _,
+                );
+
+                attr_index += 1;
+            };
+        }
+
+        macro_rules! float_attr {
+            ($type:ident, $field:ident) => {
+                gl::VertexAttribPointer(
+                    attr_index,
+                    1,
+                    gl::$type,
+                    gl::FALSE,
+                    mem::size_of::<Vertex>() as i32,
+                    memoffset::offset_of!(Vertex, $field) as *const _,
+                );
+
+                attr_index += 1;
+            };
+        }
+
+        int_attr!(UNSIGNED_INT, texture_id);
+        int_attr!(UNSIGNED_BYTE, sides);
+
+        float_attr!(UNSIGNED_INT, column);
+        float_attr!(UNSIGNED_INT, line);
+        float_attr!(UNSIGNED_SHORT, height);
+        float_attr!(UNSIGNED_SHORT, width);
+        float_attr!(UNSIGNED_SHORT, offset_x);
+        float_attr!(UNSIGNED_SHORT, offset_y);
+        float_attr!(FLOAT, base_cell_height);
+
+        for index in 0..attr_index {
+            gl::EnableVertexAttribArray(index);
+        }
+
+        gl::BindVertexArray(0);
+        gl::BindBuffer(gl::ARRAY_BUFFER, 0);
+    }
+
+    (vao, vbo)
+}
diff --git a/alacritty/src/renderer/mod.rs b/alacritty/src/renderer/mod.rs
index 11ccfc63..71ed6e28 100644
--- a/alacritty/src/renderer/mod.rs
+++ b/alacritty/src/renderer/mod.rs
@@ -14,6 +14,7 @@ use fnv::FnvHasher;
 use log::{error, info};
 use unicode_width::UnicodeWidthChar;
 
+use alacritty_terminal::graphics::UpdateQueues;
 use alacritty_terminal::index::Point;
 use alacritty_terminal::term::cell::Flags;
 use alacritty_terminal::term::color::Rgb;
@@ -24,8 +25,10 @@ use crate::config::ui_config::{Delta, UiConfig};
 use crate::display::content::RenderableCell;
 use crate::gl;
 use crate::gl::types::*;
+use crate::renderer::graphics::GraphicsRenderer;
 use crate::renderer::rects::{RectRenderer, RenderRect};
 
+pub mod graphics;
 pub mod rects;
 
 // Shader source.
@@ -439,6 +442,7 @@ pub struct QuadRenderer {
     batch: Batch,
 
     rect_renderer: RectRenderer,
+    graphics_renderer: GraphicsRenderer,
 }
 
 #[derive(Debug)]
@@ -638,6 +642,7 @@ impl QuadRenderer {
         let mut renderer = Self {
             program,
             rect_renderer: RectRenderer::new()?,
+            graphics_renderer: GraphicsRenderer::new()?,
             vao,
             ebo,
             vbo_instance,
@@ -682,6 +687,19 @@ impl QuadRenderer {
         }
     }
 
+    /// Run the required actions to apply changes for the graphics in the grid.
+    #[inline]
+    pub fn graphics_run_updates(&mut self, update_queues: UpdateQueues, size_info: &SizeInfo) {
+        self.graphics_renderer.run_updates(update_queues, size_info);
+    }
+
+    /// Draw graphics visible in the display.
+    #[inline]
+    pub fn graphics_draw(&mut self, render_list: graphics::RenderList, size_info: &SizeInfo) {
+        self.graphics_renderer.draw(render_list, size_info);
+        self.active_tex = 0;
+    }
+
     pub fn with_api<F, T>(&mut self, config: &UiConfig, props: &SizeInfo, func: F) -> T
     where
         F: FnOnce(RenderApi<'_>) -> T,
@@ -842,6 +860,7 @@ impl<'a> RenderApi<'a> {
                 point: Point::new(point.line, point.column + i),
                 character,
                 zerowidth: None,
+                graphic: None,
                 flags: Flags::empty(),
                 bg_alpha: 1.0,
                 fg,
diff --git a/alacritty/src/url.rs b/alacritty/src/url.rs
new file mode 100644
index 00000000..84b8584f
--- /dev/null
+++ b/alacritty/src/url.rs
@@ -0,0 +1,276 @@
+use std::cmp::min;
+use std::mem;
+
+use crossfont::Metrics;
+use glutin::event::{ElementState, ModifiersState};
+use urlocator::{UrlLocation, UrlLocator};
+
+use alacritty_terminal::index::{Column, Point};
+use alacritty_terminal::term::cell::Flags;
+use alacritty_terminal::term::color::Rgb;
+use alacritty_terminal::term::SizeInfo;
+
+use crate::config::Config;
+use crate::display::content::RenderableCell;
+use crate::event::Mouse;
+use crate::renderer::rects::{RenderLine, RenderRect};
+
+#[derive(Clone, Debug, PartialEq, Eq)]
+pub struct Url {
+    lines: Vec<RenderLine>,
+    end_offset: u16,
+    num_cols: Column,
+}
+
+impl Url {
+    pub fn rects(&self, metrics: &Metrics, size: &SizeInfo) -> Vec<RenderRect> {
+        let end = self.end();
+        self.lines
+            .iter()
+            .filter(|line| line.start <= end)
+            .map(|line| {
+                let mut rect_line = *line;
+                rect_line.end = min(line.end, end);
+                rect_line.rects(Flags::UNDERLINE, metrics, size)
+            })
+            .flatten()
+            .collect()
+    }
+
+    pub fn start(&self) -> Point {
+        self.lines[0].start
+    }
+
+    pub fn end(&self) -> Point {
+        self.lines[self.lines.len() - 1].end.sub(self.num_cols, self.end_offset as usize)
+    }
+}
+
+pub struct Urls {
+    locator: UrlLocator,
+    urls: Vec<Url>,
+    scheme_buffer: Vec<(Point, Rgb)>,
+    last_point: Option<Point>,
+    state: UrlLocation,
+}
+
+impl Default for Urls {
+    fn default() -> Self {
+        Self {
+            locator: UrlLocator::new(),
+            scheme_buffer: Vec::new(),
+            urls: Vec::new(),
+            state: UrlLocation::Reset,
+            last_point: None,
+        }
+    }
+}
+
+impl Urls {
+    pub fn new() -> Self {
+        Self::default()
+    }
+
+    // Update tracked URLs.
+    pub fn update(&mut self, num_cols: Column, cell: &RenderableCell) {
+        let point = cell.point;
+        let mut end = point;
+
+        // Include the following wide char spacer.
+        if cell.flags.contains(Flags::WIDE_CHAR) {
+            end.column += 1;
+        }
+
+        // Reset URL when empty cells have been skipped.
+        if point != Point::default() && Some(point.sub(num_cols, 1)) != self.last_point {
+            self.reset();
+        }
+
+        self.last_point = Some(end);
+
+        // Extend current state if a leading wide char spacer is encountered.
+        if cell.flags.intersects(Flags::LEADING_WIDE_CHAR_SPACER) {
+            if let UrlLocation::Url(_, mut end_offset) = self.state {
+                if end_offset != 0 {
+                    end_offset += 1;
+                }
+
+                self.extend_url(point, end, cell.fg, end_offset);
+            }
+
+            return;
+        }
+
+        // Advance parser.
+        let last_state = mem::replace(&mut self.state, self.locator.advance(cell.character));
+        match (self.state, last_state) {
+            (UrlLocation::Url(_length, end_offset), UrlLocation::Scheme) => {
+                // Create empty URL.
+                self.urls.push(Url { lines: Vec::new(), end_offset, num_cols });
+
+                // Push schemes into URL.
+                for (scheme_point, scheme_fg) in self.scheme_buffer.split_off(0) {
+                    self.extend_url(scheme_point, scheme_point, scheme_fg, end_offset);
+                }
+
+                // Push the new cell into URL.
+                self.extend_url(point, end, cell.fg, end_offset);
+            },
+            (UrlLocation::Url(_length, end_offset), UrlLocation::Url(..)) => {
+                self.extend_url(point, end, cell.fg, end_offset);
+            },
+            (UrlLocation::Scheme, _) => self.scheme_buffer.push((cell.point, cell.fg)),
+            (UrlLocation::Reset, _) => self.reset(),
+            _ => (),
+        }
+
+        // Reset at un-wrapped linebreak.
+        if cell.point.column + 1 == num_cols && !cell.flags.contains(Flags::WRAPLINE) {
+            self.reset();
+        }
+    }
+
+    /// Extend the last URL.
+    fn extend_url(&mut self, start: Point, end: Point, color: Rgb, end_offset: u16) {
+        let url = self.urls.last_mut().unwrap();
+
+        // If color changed, we need to insert a new line.
+        if url.lines.last().map(|last| last.color) == Some(color) {
+            url.lines.last_mut().unwrap().end = end;
+        } else {
+            url.lines.push(RenderLine { color, start, end });
+        }
+
+        // Update excluded cells at the end of the URL.
+        url.end_offset = end_offset;
+    }
+
+    /// Find URL below the mouse cursor.
+    pub fn highlighted(
+        &self,
+        config: &Config,
+        mouse: &Mouse,
+        mods: ModifiersState,
+        mouse_mode: bool,
+        selection: bool,
+    ) -> Option<Url> {
+        // Require additional shift in mouse mode.
+        let mut required_mods = config.ui_config.mouse.url.mods();
+        if mouse_mode {
+            required_mods |= ModifiersState::SHIFT;
+        }
+
+        // Make sure all prerequisites for highlighting are met.
+        if selection
+            || !mouse.inside_text_area
+            || config.ui_config.mouse.url.launcher.is_none()
+            || required_mods != mods
+            || mouse.left_button_state == ElementState::Pressed
+        {
+            return None;
+        }
+
+        self.find_at(Point::new(mouse.line, mouse.column))
+    }
+
+    /// Find URL at location.
+    pub fn find_at(&self, point: Point) -> Option<Url> {
+        for url in &self.urls {
+            if (url.start()..=url.end()).contains(&point) {
+                return Some(url.clone());
+            }
+        }
+        None
+    }
+
+    fn reset(&mut self) {
+        self.locator = UrlLocator::new();
+        self.state = UrlLocation::Reset;
+        self.scheme_buffer.clear();
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    use alacritty_terminal::index::{Column, Line};
+
+    fn text_to_cells(text: &str) -> Vec<RenderableCell> {
+        text.chars()
+            .enumerate()
+            .map(|(i, character)| RenderableCell {
+                character,
+                zerowidth: None,
+                graphic: None,
+                point: Point::new(Line(0), Column(i)),
+                fg: Default::default(),
+                bg: Default::default(),
+                bg_alpha: 0.,
+                flags: Flags::empty(),
+                is_match: false,
+            })
+            .collect()
+    }
+
+    #[test]
+    fn multi_color_url() {
+        let mut input = text_to_cells("test https://example.org ing");
+        let num_cols = input.len();
+
+        input[10].fg = Rgb { r: 0xff, g: 0x00, b: 0xff };
+
+        let mut urls = Urls::new();
+
+        for cell in input {
+            urls.update(Column(num_cols), &cell);
+        }
+
+        let url = urls.urls.first().unwrap();
+        assert_eq!(url.start().column, Column(5));
+        assert_eq!(url.end().column, Column(23));
+    }
+
+    #[test]
+    fn multiple_urls() {
+        let input = text_to_cells("test git:a git:b git:c ing");
+        let num_cols = input.len();
+
+        let mut urls = Urls::new();
+
+        for cell in input {
+            urls.update(Column(num_cols), &cell);
+        }
+
+        assert_eq!(urls.urls.len(), 3);
+
+        assert_eq!(urls.urls[0].start().column, Column(5));
+        assert_eq!(urls.urls[0].end().column, Column(9));
+
+        assert_eq!(urls.urls[1].start().column, Column(11));
+        assert_eq!(urls.urls[1].end().column, Column(15));
+
+        assert_eq!(urls.urls[2].start().column, Column(17));
+        assert_eq!(urls.urls[2].end().column, Column(21));
+    }
+
+    #[test]
+    fn wide_urls() {
+        let input = text_to_cells("test https://こんにちは (http:여보세요) ing");
+        let num_cols = input.len() + 9;
+
+        let mut urls = Urls::new();
+
+        for cell in input {
+            urls.update(Column(num_cols), &cell);
+        }
+
+        assert_eq!(urls.urls.len(), 2);
+
+        assert_eq!(urls.urls[0].start().column, Column(5));
+        assert_eq!(urls.urls[0].end().column, Column(17));
+
+        assert_eq!(urls.urls[1].start().column, Column(20));
+        assert_eq!(urls.urls[1].end().column, Column(28));
+    }
+}