Match Windows logic for picking RGB/BGR textures. (#55121)

The existing code had a lot of additional checks that didn't seem to
need to be there.

BGR could be passed back to Flutter, but this was never used in creating
the texture.

There has been a report of a Flutter app on Linux with swapped red and
blue color channels, so this seems like it is likely not working on some
drivers.

The original logic was introduced in
f104bad

Author: robert-ancell

shell/platform/linux/fl_framebuffer.cc

@@ -39,7 +39,7 @@ static void fl_framebuffer_class_init(FlFramebufferClass* klass) {
 
 static void fl_framebuffer_init(FlFramebuffer* self) {}
 
-FlFramebuffer* fl_framebuffer_new(size_t width, size_t height) {
+FlFramebuffer* fl_framebuffer_new(GLint format, size_t width, size_t height) {
   FlFramebuffer* provider =
       FL_FRAMEBUFFER(g_object_new(fl_framebuffer_get_type(), nullptr));
 
@@ -56,12 +56,12 @@ FlFramebuffer* fl_framebuffer_new(size_t width, size_t height) {
   glTexParameterf(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_NEAREST);
   glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_CLAMP_TO_EDGE);
   glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_CLAMP_TO_EDGE);
-  glTexImage2D(GL_TEXTURE_2D, 0, GL_RGBA8, width, height, 0, GL_RGBA,
+  glTexImage2D(GL_TEXTURE_2D, 0, format, width, height, 0, format,
                GL_UNSIGNED_BYTE, NULL);
   glBindTexture(GL_TEXTURE_2D, 0);
 
-  glFramebufferTexture2D(GL_FRAMEBUFFER_EXT, GL_COLOR_ATTACHMENT0_EXT,
-                         GL_TEXTURE_2D, provider->texture_id, 0);
+  glFramebufferTexture2D(GL_FRAMEBUFFER, GL_COLOR_ATTACHMENT0, GL_TEXTURE_2D,
+                         provider->texture_id, 0);
 
   return provider;
 }
@@ -78,31 +78,6 @@ GLenum fl_framebuffer_get_target(FlFramebuffer* self) {
   return GL_TEXTURE_2D;
 }
 
-GLenum fl_framebuffer_get_format(FlFramebuffer* self) {
-  // Flutter defines SK_R32_SHIFT=16, so SK_PMCOLOR_BYTE_ORDER should be BGRA.
-  // In Linux kN32_SkColorType is assumed to be kBGRA_8888_SkColorType.
-  // So we must choose a valid gl format to be compatible with surface format
-  // BGRA8.
-  // Following logic is copied from Skia GrGLCaps.cpp:
-  // https://github.com/google/skia/blob/4738ed711e03212aceec3cd502a4adb545f38e63/src/gpu/ganesh/gl/GrGLCaps.cpp#L1963-L2116
-
-  if (epoxy_is_desktop_gl()) {
-    // For OpenGL.
-    if (epoxy_gl_version() >= 12 || epoxy_has_gl_extension("GL_EXT_bgra")) {
-      return GL_RGBA8;
-    }
-  } else {
-    // For OpenGL ES.
-    if (epoxy_has_gl_extension("GL_EXT_texture_format_BGRA8888") ||
-        (epoxy_has_gl_extension("GL_APPLE_texture_format_BGRA8888") &&
-         epoxy_gl_version() >= 30)) {
-      return GL_BGRA8_EXT;
-    }
-  }
-  g_critical("Failed to determine valid GL format for Flutter rendering");
-  return GL_RGBA8;
-}
-
 size_t fl_framebuffer_get_width(FlFramebuffer* self) {
   return self->width;
 }

shell/platform/linux/fl_framebuffer.h

@@ -21,14 +21,15 @@ G_DECLARE_FINAL_TYPE(FlFramebuffer, fl_framebuffer, FL, FRAMEBUFFER, GObject)
 
 /**
  * fl_framebuffer_new:
+ * @format: format, e.g. GL_RGB, GL_BGR
  * @width: width of texture.
  * @height: height of texture.
  *
  * Creates a new frame buffer. Requires a valid OpenGL context to create.
  *
  * Returns: a new #FlFramebuffer.
  */
-FlFramebuffer* fl_framebuffer_new(size_t width, size_t height);
+FlFramebuffer* fl_framebuffer_new(GLint format, size_t width, size_t height);
 
 /**
  * fl_framebuffer_get_id:
@@ -60,16 +61,6 @@ GLuint fl_framebuffer_get_texture_id(FlFramebuffer* framebuffer);
  */
 GLenum fl_framebuffer_get_target(FlFramebuffer* framebuffer);
 
-/**
- * fl_framebuffer_get_format:
- * @framebuffer: an #FlFramebuffer.
- *
- * Gets format of texture backing the framebuffer (example GL_RGBA8).
- *
- * Returns: texture format.
- */
-GLenum fl_framebuffer_get_format(FlFramebuffer* framebuffer);
-
 /**
  * fl_framebuffer_get_width:
  * @framebuffer: an #FlFramebuffer.

shell/platform/linux/fl_renderer.cc

@@ -42,6 +42,15 @@ typedef struct {
   // Engine we are rendering.
   GWeakRef engine;
 
+  // Flag to track lazy initialization.
+  gboolean initialized;
+
+  // The pixel format passed to the engine.
+  GLint sized_format;
+
+  // The format used to create textures.
+  GLint general_format;
+
   // Views being rendered.
   GHashTable* views;
 
@@ -105,6 +114,25 @@ static GLfloat pixels_to_gl_coords(GLfloat position, GLfloat pixels) {
   return (2.0 * position / pixels) - 1.0;
 }
 
+// Perform single run OpenGL initialization.
+static void initialize(FlRenderer* self) {
+  FlRendererPrivate* priv = reinterpret_cast<FlRendererPrivate*>(
+      fl_renderer_get_instance_private(self));
+
+  if (priv->initialized) {
+    return;
+  }
+  priv->initialized = TRUE;
+
+  if (epoxy_has_gl_extension("GL_EXT_texture_format_BGRA8888")) {
+    priv->sized_format = GL_BGRA8_EXT;
+    priv->general_format = GL_BGRA_EXT;
+  } else {
+    priv->sized_format = GL_RGBA8;
+    priv->general_format = GL_RGBA;
+  }
+}
+
 static void fl_renderer_unblock_main_thread(FlRenderer* self) {
   FlRendererPrivate* priv = reinterpret_cast<FlRendererPrivate*>(
       fl_renderer_get_instance_private(self));
@@ -328,13 +356,18 @@ guint32 fl_renderer_get_fbo(FlRenderer* self) {
 }
 
 gboolean fl_renderer_create_backing_store(
-    FlRenderer* renderer,
+    FlRenderer* self,
     const FlutterBackingStoreConfig* config,
     FlutterBackingStore* backing_store_out) {
-  fl_renderer_make_current(renderer);
+  FlRendererPrivate* priv = reinterpret_cast<FlRendererPrivate*>(
+      fl_renderer_get_instance_private(self));
+
+  fl_renderer_make_current(self);
+
+  initialize(self);
 
-  FlFramebuffer* framebuffer =
-      fl_framebuffer_new(config->size.width, config->size.height);
+  FlFramebuffer* framebuffer = fl_framebuffer_new(
+      priv->general_format, config->size.width, config->size.height);
   if (!framebuffer) {
     g_warning("Failed to create backing store");
     return FALSE;
@@ -345,8 +378,7 @@ gboolean fl_renderer_create_backing_store(
   backing_store_out->open_gl.framebuffer.user_data = framebuffer;
   backing_store_out->open_gl.framebuffer.name =
       fl_framebuffer_get_id(framebuffer);
-  backing_store_out->open_gl.framebuffer.target =
-      fl_framebuffer_get_format(framebuffer);
+  backing_store_out->open_gl.framebuffer.target = priv->sized_format;
   backing_store_out->open_gl.framebuffer.destruction_callback = [](void* p) {
     // Backing store destroyed in fl_renderer_collect_backing_store(), set
     // on FlutterCompositor.collect_backing_store_callback during engine start.

shell/platform/linux/fl_renderer_test.cc

@@ -52,7 +52,8 @@ TEST(FlRendererTest, RestoresGLState) {
   g_autoptr(FlDartProject) project = fl_dart_project_new();
   g_autoptr(FlView) view = fl_view_new(project);
   g_autoptr(FlMockRenderer) renderer = fl_mock_renderer_new();
-  g_autoptr(FlFramebuffer) framebuffer = fl_framebuffer_new(kWidth, kHeight);
+  g_autoptr(FlFramebuffer) framebuffer =
+      fl_framebuffer_new(GL_RGB, kWidth, kHeight);
 
   fl_renderer_add_view(FL_RENDERER(renderer), 0, view);
   fl_renderer_wait_for_frame(FL_RENDERER(renderer), kWidth, kHeight);
@@ -144,6 +145,8 @@ TEST(FlRendererTest, BlitFramebufferExtension) {
           ::testing::Return(reinterpret_cast<const GLubyte*>("Intel")));
   ON_CALL(epoxy, epoxy_is_desktop_gl).WillByDefault(::testing::Return(true));
   EXPECT_CALL(epoxy, epoxy_gl_version).WillRepeatedly(::testing::Return(20));
+  EXPECT_CALL(epoxy, epoxy_has_gl_extension(::testing::_))
+      .WillRepeatedly(::testing::Return(false));
   EXPECT_CALL(epoxy, epoxy_has_gl_extension(
                          ::testing::StrEq("GL_EXT_framebuffer_blit")))
       .WillRepeatedly(::testing::Return(true));