[Windows] Refactor the GLES proc table (#48688)

GLES functions are resolved at runtime. This refactors how these functions are stored by introducing the `GlProcTable` abstraction.

This is a step towards switching the Windows embedder to `FlutterCompositor` rendering as the present callback will use the `GlProcTable` to render OpenGL backing stores.
 
Part of flutter/flutter#128904

[C++, Objective-C, Java style guides]: https://github.com/flutter/engine/blob/main/CONTRIBUTING.md#style

Author: loic-sharma

ci/licenses_golden/licenses_flutter

@@ -7138,6 +7138,8 @@ ORIGIN: ../../../flutter/shell/platform/windows/flutter_windows_texture_registra
 ORIGIN: ../../../flutter/shell/platform/windows/flutter_windows_view.cc + ../../../flutter/LICENSE
 ORIGIN: ../../../flutter/shell/platform/windows/flutter_windows_view.h + ../../../flutter/LICENSE
 ORIGIN: ../../../flutter/shell/platform/windows/flutter_windows_view_controller.h + ../../../flutter/LICENSE
+ORIGIN: ../../../flutter/shell/platform/windows/gl_proc_table.cc + ../../../flutter/LICENSE
+ORIGIN: ../../../flutter/shell/platform/windows/gl_proc_table.h + ../../../flutter/LICENSE
 ORIGIN: ../../../flutter/shell/platform/windows/keyboard_handler_base.h + ../../../flutter/LICENSE
 ORIGIN: ../../../flutter/shell/platform/windows/keyboard_key_channel_handler.cc + ../../../flutter/LICENSE
 ORIGIN: ../../../flutter/shell/platform/windows/keyboard_key_channel_handler.h + ../../../flutter/LICENSE
@@ -9961,6 +9963,8 @@ FILE: ../../../flutter/shell/platform/windows/flutter_windows_texture_registrar.
 FILE: ../../../flutter/shell/platform/windows/flutter_windows_view.cc
 FILE: ../../../flutter/shell/platform/windows/flutter_windows_view.h
 FILE: ../../../flutter/shell/platform/windows/flutter_windows_view_controller.h
+FILE: ../../../flutter/shell/platform/windows/gl_proc_table.cc
+FILE: ../../../flutter/shell/platform/windows/gl_proc_table.h
 FILE: ../../../flutter/shell/platform/windows/keyboard_handler_base.h
 FILE: ../../../flutter/shell/platform/windows/keyboard_key_channel_handler.cc
 FILE: ../../../flutter/shell/platform/windows/keyboard_key_channel_handler.h

shell/platform/windows/BUILD.gn

@@ -70,6 +70,8 @@ source_set("flutter_windows_source") {
     "flutter_windows_view.cc",
     "flutter_windows_view.h",
     "flutter_windows_view_controller.h",
+    "gl_proc_table.cc",
+    "gl_proc_table.h",
     "keyboard_handler_base.h",
     "keyboard_key_channel_handler.cc",
     "keyboard_key_channel_handler.h",
@@ -198,7 +200,7 @@ executable("flutter_windows_unittests") {
     "testing/flutter_windows_engine_builder.cc",
     "testing/flutter_windows_engine_builder.h",
     "testing/mock_direct_manipulation.h",
-    "testing/mock_gl_functions.h",
+    "testing/mock_gl_proc_table.h",
     "testing/mock_text_input_manager.cc",
     "testing/mock_text_input_manager.h",
     "testing/mock_window.cc",

shell/platform/windows/external_texture.h

@@ -12,30 +12,6 @@
 
 namespace flutter {
 
-typedef void (*glGenTexturesProc)(GLsizei n, GLuint* textures);
-typedef void (*glDeleteTexturesProc)(GLsizei n, const GLuint* textures);
-typedef void (*glBindTextureProc)(GLenum target, GLuint texture);
-typedef void (*glTexParameteriProc)(GLenum target, GLenum pname, GLint param);
-typedef void (*glTexImage2DProc)(GLenum target,
-                                 GLint level,
-                                 GLint internalformat,
-                                 GLsizei width,
-                                 GLsizei height,
-                                 GLint border,
-                                 GLenum format,
-                                 GLenum type,
-                                 const void* data);
-
-// A struct containing pointers to resolved gl* functions.
-struct GlProcs {
-  glGenTexturesProc glGenTextures;
-  glDeleteTexturesProc glDeleteTextures;
-  glBindTextureProc glBindTexture;
-  glTexParameteriProc glTexParameteri;
-  glTexImage2DProc glTexImage2D;
-  bool valid;
-};
-
 // Abstract external texture.
 class ExternalTexture {
  public:

shell/platform/windows/external_texture_d3d.cc

@@ -14,18 +14,18 @@ ExternalTextureD3d::ExternalTextureD3d(
     const FlutterDesktopGpuSurfaceTextureCallback texture_callback,
     void* user_data,
     const AngleSurfaceManager* surface_manager,
-    const GlProcs& gl_procs)
+    std::shared_ptr<GlProcTable> gl)
     : type_(type),
       texture_callback_(texture_callback),
       user_data_(user_data),
       surface_manager_(surface_manager),
-      gl_(gl_procs) {}
+      gl_(std::move(gl)) {}
 
 ExternalTextureD3d::~ExternalTextureD3d() {
   ReleaseImage();
 
   if (gl_texture_ != 0) {
-    gl_.glDeleteTextures(1, &gl_texture_);
+    gl_->DeleteTextures(1, &gl_texture_);
   }
 }
 
@@ -69,15 +69,15 @@ bool ExternalTextureD3d::CreateOrUpdateTexture(
   }
 
   if (gl_texture_ == 0) {
-    gl_.glGenTextures(1, &gl_texture_);
+    gl_->GenTextures(1, &gl_texture_);
 
-    gl_.glBindTexture(GL_TEXTURE_2D, gl_texture_);
-    gl_.glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_CLAMP_TO_EDGE);
-    gl_.glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_CLAMP_TO_EDGE);
-    gl_.glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR);
-    gl_.glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR);
+    gl_->BindTexture(GL_TEXTURE_2D, gl_texture_);
+    gl_->TexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_CLAMP_TO_EDGE);
+    gl_->TexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_CLAMP_TO_EDGE);
+    gl_->TexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR);
+    gl_->TexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR);
   } else {
-    gl_.glBindTexture(GL_TEXTURE_2D, gl_texture_);
+    gl_->BindTexture(GL_TEXTURE_2D, gl_texture_);
   }
 
   auto handle = SAFE_ACCESS(descriptor, handle, nullptr);

shell/platform/windows/external_texture_d3d.h

@@ -5,9 +5,12 @@
 #ifndef FLUTTER_SHELL_PLATFORM_WINDOWS_EXTERNAL_TEXTURE_D3D_H_
 #define FLUTTER_SHELL_PLATFORM_WINDOWS_EXTERNAL_TEXTURE_D3D_H_
 
+#include <memory>
+
 #include "flutter/fml/macros.h"
 #include "flutter/shell/platform/windows/angle_surface_manager.h"
 #include "flutter/shell/platform/windows/external_texture.h"
+#include "flutter/shell/platform/windows/gl_proc_table.h"
 
 namespace flutter {
 
@@ -19,7 +22,7 @@ class ExternalTextureD3d : public ExternalTexture {
       const FlutterDesktopGpuSurfaceTextureCallback texture_callback,
       void* user_data,
       const AngleSurfaceManager* surface_manager,
-      const GlProcs& gl_procs);
+      std::shared_ptr<GlProcTable> gl);
   virtual ~ExternalTextureD3d();
 
   // |ExternalTexture|
@@ -39,7 +42,7 @@ class ExternalTextureD3d : public ExternalTexture {
   const FlutterDesktopGpuSurfaceTextureCallback texture_callback_;
   void* const user_data_;
   const AngleSurfaceManager* surface_manager_;
-  const GlProcs& gl_;
+  std::shared_ptr<GlProcTable> gl_;
   GLuint gl_texture_ = 0;
   EGLSurface egl_surface_ = EGL_NO_SURFACE;
   void* last_surface_handle_ = nullptr;

shell/platform/windows/external_texture_pixelbuffer.cc

@@ -9,14 +9,14 @@ namespace flutter {
 ExternalTexturePixelBuffer::ExternalTexturePixelBuffer(
     const FlutterDesktopPixelBufferTextureCallback texture_callback,
     void* user_data,
-    const GlProcs& gl_procs)
+    std::shared_ptr<GlProcTable> gl)
     : texture_callback_(texture_callback),
       user_data_(user_data),
-      gl_(gl_procs) {}
+      gl_(std::move(gl)) {}
 
 ExternalTexturePixelBuffer::~ExternalTexturePixelBuffer() {
   if (gl_texture_ != 0) {
-    gl_.glDeleteTextures(1, &gl_texture_);
+    gl_->DeleteTextures(1, &gl_texture_);
   }
 }
 
@@ -51,20 +51,20 @@ bool ExternalTexturePixelBuffer::CopyPixelBuffer(size_t& width,
   height = pixel_buffer->height;
 
   if (gl_texture_ == 0) {
-    gl_.glGenTextures(1, &gl_texture_);
+    gl_->GenTextures(1, &gl_texture_);
 
-    gl_.glBindTexture(GL_TEXTURE_2D, gl_texture_);
-    gl_.glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_CLAMP_TO_EDGE);
-    gl_.glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_CLAMP_TO_EDGE);
-    gl_.glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR);
-    gl_.glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR);
+    gl_->BindTexture(GL_TEXTURE_2D, gl_texture_);
+    gl_->TexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_CLAMP_TO_EDGE);
+    gl_->TexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_CLAMP_TO_EDGE);
+    gl_->TexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR);
+    gl_->TexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR);
 
   } else {
-    gl_.glBindTexture(GL_TEXTURE_2D, gl_texture_);
+    gl_->BindTexture(GL_TEXTURE_2D, gl_texture_);
   }
-  gl_.glTexImage2D(GL_TEXTURE_2D, 0, GL_RGBA, pixel_buffer->width,
-                   pixel_buffer->height, 0, GL_RGBA, GL_UNSIGNED_BYTE,
-                   pixel_buffer->buffer);
+  gl_->TexImage2D(GL_TEXTURE_2D, 0, GL_RGBA, pixel_buffer->width,
+                  pixel_buffer->height, 0, GL_RGBA, GL_UNSIGNED_BYTE,
+                  pixel_buffer->buffer);
   if (pixel_buffer->release_callback) {
     pixel_buffer->release_callback(pixel_buffer->release_context);
   }

shell/platform/windows/external_texture_pixelbuffer.h

@@ -8,6 +8,7 @@
 #include "flutter/fml/macros.h"
 #include "flutter/shell/platform/common/public/flutter_texture_registrar.h"
 #include "flutter/shell/platform/windows/external_texture.h"
+#include "flutter/shell/platform/windows/gl_proc_table.h"
 
 namespace flutter {
 
@@ -17,7 +18,7 @@ class ExternalTexturePixelBuffer : public ExternalTexture {
   ExternalTexturePixelBuffer(
       const FlutterDesktopPixelBufferTextureCallback texture_callback,
       void* user_data,
-      const GlProcs& gl_procs);
+      std::shared_ptr<GlProcTable> gl);
 
   virtual ~ExternalTexturePixelBuffer();
 
@@ -37,7 +38,7 @@ class ExternalTexturePixelBuffer : public ExternalTexture {
 
   const FlutterDesktopPixelBufferTextureCallback texture_callback_ = nullptr;
   void* const user_data_ = nullptr;
-  const GlProcs& gl_;
+  std::shared_ptr<GlProcTable> gl_;
   GLuint gl_texture_ = 0;
 
   FML_DISALLOW_COPY_AND_ASSIGN(ExternalTexturePixelBuffer);

shell/platform/windows/flutter_windows_engine.cc

@@ -168,6 +168,8 @@ FlutterWindowsEngine::FlutterWindowsEngine(
     windows_proc_table_ = std::make_shared<WindowsProcTable>();
   }
 
+  gl_ = GlProcTable::Create();
+
   embedder_api_.struct_size = sizeof(FlutterEngineProcTable);
   FlutterEngineGetProcAddresses(&embedder_api_);
 
@@ -204,9 +206,8 @@ FlutterWindowsEngine::FlutterWindowsEngine(
       },
       static_cast<void*>(this));
 
-  FlutterWindowsTextureRegistrar::ResolveGlFunctions(gl_procs_);
   texture_registrar_ =
-      std::make_unique<FlutterWindowsTextureRegistrar>(this, gl_procs_);
+      std::make_unique<FlutterWindowsTextureRegistrar>(this, gl_);
 
   // Check for impeller support.
   auto& switches = project_->GetSwitches();

shell/platform/windows/flutter_windows_engine.h

@@ -360,9 +360,6 @@ class FlutterWindowsEngine {
   // The texture registrar.
   std::unique_ptr<FlutterWindowsTextureRegistrar> texture_registrar_;
 
-  // Resolved OpenGL functions used by external texture implementations.
-  GlProcs gl_procs_ = {};
-
   // An object used for intializing Angle and creating / destroying render
   // surfaces. Surface creation functionality requires a valid render_target.
   // May be nullptr if ANGLE failed to initialize.
@@ -422,6 +419,8 @@ class FlutterWindowsEngine {
 
   std::shared_ptr<WindowsProcTable> windows_proc_table_;
 
+  std::shared_ptr<GlProcTable> gl_;
+
   FML_DISALLOW_COPY_AND_ASSIGN(FlutterWindowsEngine);
 };
 

shell/platform/windows/flutter_windows_texture_registrar.cc

@@ -20,12 +20,12 @@ namespace flutter {
 
 FlutterWindowsTextureRegistrar::FlutterWindowsTextureRegistrar(
     FlutterWindowsEngine* engine,
-    const GlProcs& gl_procs)
-    : engine_(engine), gl_procs_(gl_procs) {}
+    std::shared_ptr<GlProcTable> gl)
+    : engine_(engine), gl_(std::move(gl)) {}
 
 int64_t FlutterWindowsTextureRegistrar::RegisterTexture(
     const FlutterDesktopTextureInfo* texture_info) {
-  if (!gl_procs_.valid) {
+  if (!gl_) {
     return kInvalidTexture;
   }
 
@@ -37,7 +37,7 @@ int64_t FlutterWindowsTextureRegistrar::RegisterTexture(
 
     return EmplaceTexture(std::make_unique<flutter::ExternalTexturePixelBuffer>(
         texture_info->pixel_buffer_config.callback,
-        texture_info->pixel_buffer_config.user_data, gl_procs_));
+        texture_info->pixel_buffer_config.user_data, gl_));
   } else if (texture_info->type == kFlutterDesktopGpuSurfaceTexture) {
     const FlutterDesktopGpuSurfaceTextureConfig* gpu_surface_config =
         &texture_info->gpu_surface_config;
@@ -53,8 +53,7 @@ int64_t FlutterWindowsTextureRegistrar::RegisterTexture(
 
       auto user_data = SAFE_ACCESS(gpu_surface_config, user_data, nullptr);
       return EmplaceTexture(std::make_unique<flutter::ExternalTextureD3d>(
-          surface_type, callback, user_data, engine_->surface_manager(),
-          gl_procs_));
+          surface_type, callback, user_data, engine_->surface_manager(), gl_));
     }
   }
 
@@ -126,21 +125,4 @@ bool FlutterWindowsTextureRegistrar::PopulateTexture(
   return texture->PopulateTexture(width, height, opengl_texture);
 }
 
-void FlutterWindowsTextureRegistrar::ResolveGlFunctions(GlProcs& procs) {
-  procs.glGenTextures =
-      reinterpret_cast<glGenTexturesProc>(eglGetProcAddress("glGenTextures"));
-  procs.glDeleteTextures = reinterpret_cast<glDeleteTexturesProc>(
-      eglGetProcAddress("glDeleteTextures"));
-  procs.glBindTexture =
-      reinterpret_cast<glBindTextureProc>(eglGetProcAddress("glBindTexture"));
-  procs.glTexParameteri = reinterpret_cast<glTexParameteriProc>(
-      eglGetProcAddress("glTexParameteri"));
-  procs.glTexImage2D =
-      reinterpret_cast<glTexImage2DProc>(eglGetProcAddress("glTexImage2D"));
-
-  procs.valid = procs.glGenTextures && procs.glDeleteTextures &&
-                procs.glBindTexture && procs.glTexParameteri &&
-                procs.glTexImage2D;
-}
-
 };  // namespace flutter