Make gles2 renderer actually gles2

Fixes #6209.

8 files changed, 83 insertions, 38 deletions

diff --git a/CHANGELOG.md b/CHANGELOG.md
index 4002aa35..abada71e 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -12,6 +12,7 @@ The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/).
 - Uppercase `-T` short form for `--title`
 - Support for horizontal scrolling in mouse mode and alternative scrolling modes
 - Support for fractional scaling on Wayland with wp-fractional-scale protocol
+- Support for running on GLES context
 
 ### Changed
 
diff --git a/Cargo.lock b/Cargo.lock
index 62024fa3..041aa3b0 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -688,42 +688,42 @@ dependencies = [
 
 [[package]]
 name = "glutin"
-version = "0.30.3"
+version = "0.30.4"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "524d807cd49a0c56a53ef9a6738cd15e7c8c4e9d37a3b7fdb3c250c1cd5bf7a3"
+checksum = "373e3fbcfa6b9c313faa03625a08268168ba9be1003d1ecfcebd5266388aa131"
 dependencies = [
  "bitflags",
  "cfg_aliases",
  "cgl",
- "cocoa",
  "core-foundation",
+ "dispatch",
  "glutin_egl_sys",
  "glutin_glx_sys",
  "glutin_wgl_sys",
  "libloading",
- "objc",
+ "objc2",
  "once_cell",
  "raw-window-handle",
  "wayland-sys 0.30.0",
- "windows-sys 0.36.1",
+ "windows-sys 0.45.0",
  "x11-dl",
 ]
 
 [[package]]
 name = "glutin_egl_sys"
-version = "0.3.1"
+version = "0.4.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "3adbb8fec0e18e340f990c78f79f5f0e142d0d83f46b10909aaa7d251c00afdf"
+checksum = "e5aaf0abb5c4148685b33101ae326a207946b4d3764d6cdc79f8316cdaa8367d"
 dependencies = [
  "gl_generator",
- "windows-sys 0.36.1",
+ "windows-sys 0.45.0",
 ]
 
 [[package]]
 name = "glutin_glx_sys"
-version = "0.3.0"
+version = "0.4.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "947c4850c58211c9627969c2b4e2674764b81ae5b47bab2c9a477d7942f96e0f"
+checksum = "1b53cb5fe568964aa066a3ba91eac5ecbac869fb0842cd0dc9e412434f1a1494"
 dependencies = [
  "gl_generator",
  "x11-dl",
@@ -731,9 +731,9 @@ dependencies = [
 
 [[package]]
 name = "glutin_wgl_sys"
-version = "0.3.0"
+version = "0.4.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "20c33975a6c9d49d72c8f032a60079bf8df536954fbf9e4cee90396ace815c57"
+checksum = "ef89398e90033fc6bc65e9bd42fd29bbbfd483bda5b56dc5562f455550618165"
 dependencies = [
  "gl_generator",
 ]
diff --git a/alacritty/Cargo.toml b/alacritty/Cargo.toml
index ea26e98a..21f18bab 100644
--- a/alacritty/Cargo.toml
+++ b/alacritty/Cargo.toml
@@ -29,7 +29,7 @@ fnv = "1"
 serde = { version = "1", features = ["derive"] }
 serde_yaml = "0.8"
 serde_json = "1"
-glutin = { version = "0.30.3", default-features = false, features = ["egl", "wgl"] }
+glutin = { version = "0.30.4", default-features = false, features = ["egl", "wgl"] }
 winit = { version = "0.28.1", default-features = false, features = ["serde"] }
 notify = "5.1.0"
 parking_lot = "0.12.0"
diff --git a/alacritty/src/renderer/mod.rs b/alacritty/src/renderer/mod.rs
index fc6c357f..8f708d33 100644
--- a/alacritty/src/renderer/mod.rs
+++ b/alacritty/src/renderer/mod.rs
@@ -4,7 +4,7 @@ use std::fmt;
 use std::sync::atomic::{AtomicBool, Ordering};
 
 use crossfont::Metrics;
-use glutin::context::PossiblyCurrentContext;
+use glutin::context::{ContextApi, GlContext, PossiblyCurrentContext};
 use glutin::display::{GetGlDisplay, GlDisplay};
 use log::info;
 use once_cell::sync::OnceCell;
@@ -110,12 +110,14 @@ impl Renderer {
 
         info!("Running on {}", renderer);
 
+        let is_gles_context = matches!(context.context_api(), ContextApi::Gles(_));
+
         // Use the config option to enforce a particular renderer configuration.
         let (use_glsl3, allow_dsb) = match renderer_prefernce {
             Some(RendererPreference::Glsl3) => (true, true),
             Some(RendererPreference::Gles2) => (false, true),
             Some(RendererPreference::Gles2Pure) => (false, false),
-            None => (version.as_ref() >= "3.3", true),
+            None => (version.as_ref() >= "3.3" && !is_gles_context, true),
         };
 
         let (text_renderer, rect_renderer) = if use_glsl3 {
@@ -123,7 +125,8 @@ impl Renderer {
             let rect_renderer = RectRenderer::new(ShaderVersion::Glsl3)?;
             (text_renderer, rect_renderer)
         } else {
-            let text_renderer = TextRendererProvider::Gles2(Gles2Renderer::new(allow_dsb)?);
+            let text_renderer =
+                TextRendererProvider::Gles2(Gles2Renderer::new(allow_dsb, is_gles_context)?);
             let rect_renderer = RectRenderer::new(ShaderVersion::Gles2)?;
             (text_renderer, rect_renderer)
         };
diff --git a/alacritty/src/renderer/platform.rs b/alacritty/src/renderer/platform.rs
index 77826100..c9802e0a 100644
--- a/alacritty/src/renderer/platform.rs
+++ b/alacritty/src/renderer/platform.rs
@@ -81,21 +81,31 @@ pub fn create_gl_context(
     gl_config: &Config,
     raw_window_handle: Option<RawWindowHandle>,
 ) -> GlutinResult<NotCurrentContext> {
-    let context_attributes = ContextAttributesBuilder::new()
-        .with_context_api(ContextApi::OpenGl(Some(Version::new(3, 3))))
-        .build(raw_window_handle);
-
-    unsafe {
-        if let Ok(gl_context) = gl_display.create_context(gl_config, &context_attributes) {
-            Ok(gl_context)
-        } else {
-            let context_attributes = ContextAttributesBuilder::new()
-                .with_profile(GlProfile::Compatibility)
-                .with_context_api(ContextApi::OpenGl(Some(Version::new(2, 1))))
-                .build(raw_window_handle);
-            gl_display.create_context(gl_config, &context_attributes)
-        }
+    let mut profiles = [
+        ContextAttributesBuilder::new()
+            .with_context_api(ContextApi::OpenGl(Some(Version::new(3, 3))))
+            .build(raw_window_handle),
+        // Try gles before OpenGL 2.1 as it tends to be more stable.
+        ContextAttributesBuilder::new()
+            .with_context_api(ContextApi::Gles(Some(Version::new(2, 0))))
+            .build(raw_window_handle),
+        ContextAttributesBuilder::new()
+            .with_profile(GlProfile::Compatibility)
+            .with_context_api(ContextApi::OpenGl(Some(Version::new(2, 1))))
+            .build(raw_window_handle),
+    ]
+    .into_iter();
+
+    // Try the optimal config first.
+    let mut picked_context =
+        unsafe { gl_display.create_context(gl_config, &profiles.next().unwrap()) };
+
+    // Try the fallback ones.
+    while let (Err(_), Some(profile)) = (picked_context.as_ref(), profiles.next()) {
+        picked_context = unsafe { gl_display.create_context(gl_config, &profile) };
     }
+
+    picked_context
 }
 
 pub fn create_gl_surface(
diff --git a/alacritty/src/renderer/text/atlas.rs b/alacritty/src/renderer/text/atlas.rs
index 662d767b..0d9b6cfd 100644
--- a/alacritty/src/renderer/text/atlas.rs
+++ b/alacritty/src/renderer/text/atlas.rs
@@ -1,3 +1,4 @@
+use std::borrow::Cow;
 use std::ptr;
 
 use crossfont::{BitmapBuffer, RasterizedGlyph};
@@ -52,6 +53,11 @@ pub struct Atlas {
     ///
     /// This is used as the advance when end of row is reached.
     row_tallest: i32,
+
+    /// Gles context.
+    ///
+    /// This affects the texture loading.
+    is_gles_context: bool,
 }
 
 /// Error that can happen when inserting a texture to the Atlas.
@@ -64,7 +70,7 @@ pub enum AtlasInsertError {
 }
 
 impl Atlas {
-    pub fn new(size: i32) -> Self {
+    pub fn new(size: i32, is_gles_context: bool) -> Self {
         let mut id: GLuint = 0;
         unsafe {
             gl::PixelStorei(gl::UNPACK_ALIGNMENT, 1);
@@ -92,7 +98,15 @@ impl Atlas {
             gl::BindTexture(gl::TEXTURE_2D, 0);
         }
 
-        Self { id, width: size, height: size, row_extent: 0, row_baseline: 0, row_tallest: 0 }
+        Self {
+            id,
+            width: size,
+            height: size,
+            row_extent: 0,
+            row_baseline: 0,
+            row_tallest: 0,
+            is_gles_context,
+        }
     }
 
     pub fn clear(&mut self) {
@@ -144,11 +158,24 @@ impl Atlas {
             let (format, buffer) = match &glyph.buffer {
                 BitmapBuffer::Rgb(buffer) => {
                     multicolor = false;
-                    (gl::RGB, buffer)
+                    // Gles context doesn't allow uploading RGB data into RGBA texture, so need
+                    // explicit copy.
+                    if self.is_gles_context {
+                        let mut new_buffer = Vec::with_capacity(buffer.len() / 3 * 4);
+                        for rgb in buffer.chunks_exact(3) {
+                            new_buffer.push(rgb[0]);
+                            new_buffer.push(rgb[1]);
+                            new_buffer.push(rgb[2]);
+                            new_buffer.push(u8::MAX);
+                        }
+                        (gl::RGBA, Cow::Owned(new_buffer))
+                    } else {
+                        (gl::RGB, Cow::Borrowed(buffer))
+                    }
                 },
                 BitmapBuffer::Rgba(buffer) => {
                     multicolor = true;
-                    (gl::RGBA, buffer)
+                    (gl::RGBA, Cow::Borrowed(buffer))
                 },
             };
 
@@ -234,7 +261,7 @@ impl Atlas {
             Err(AtlasInsertError::Full) => {
                 *current_atlas += 1;
                 if *current_atlas == atlas.len() {
-                    let new = Atlas::new(ATLAS_SIZE);
+                    let new = Atlas::new(ATLAS_SIZE, atlas[*current_atlas].is_gles_context);
                     *active_tex = 0; // Atlas::new binds a texture. Ugh this is sloppy.
                     atlas.push(new);
                 }
diff --git a/alacritty/src/renderer/text/gles2.rs b/alacritty/src/renderer/text/gles2.rs
index 2f537e5c..427a60e3 100644
--- a/alacritty/src/renderer/text/gles2.rs
+++ b/alacritty/src/renderer/text/gles2.rs
@@ -37,13 +37,17 @@ pub struct Gles2Renderer {
 }
 
 impl Gles2Renderer {
-    pub fn new(allow_dsb: bool) -> Result<Self, Error> {
+    pub fn new(allow_dsb: bool, is_gles_context: bool) -> Result<Self, Error> {
         info!("Using OpenGL ES 2.0 renderer");
 
         let dual_source_blending = allow_dsb
             && (GlExtensions::contains("GL_EXT_blend_func_extended")
                 || GlExtensions::contains("GL_ARB_blend_func_extended"));
 
+        if is_gles_context {
+            info!("Running on OpenGL ES context");
+        }
+
         if dual_source_blending {
             info!("Using dual source blending");
         }
@@ -145,7 +149,7 @@ impl Gles2Renderer {
             vao,
             vbo,
             ebo,
-            atlas: vec![Atlas::new(ATLAS_SIZE)],
+            atlas: vec![Atlas::new(ATLAS_SIZE, is_gles_context)],
             batch: Batch::new(),
             current_atlas: 0,
             active_tex: 0,
diff --git a/alacritty/src/renderer/text/glsl3.rs b/alacritty/src/renderer/text/glsl3.rs
index 885023a0..7c32bf9f 100644
--- a/alacritty/src/renderer/text/glsl3.rs
+++ b/alacritty/src/renderer/text/glsl3.rs
@@ -137,7 +137,7 @@ impl Glsl3Renderer {
             vao,
             ebo,
             vbo_instance,
-            atlas: vec![Atlas::new(ATLAS_SIZE)],
+            atlas: vec![Atlas::new(ATLAS_SIZE, false)],
             current_atlas: 0,
             active_tex: 0,
             batch: Batch::new(),