[embedder] Add FBO callback that takes frame info

shell/common/shell_test_platform_view_gl.cc

@@ -60,7 +60,7 @@ bool ShellTestPlatformViewGL::GLContextPresent() {
 }
 
 // |GPUSurfaceGLDelegate|
-intptr_t ShellTestPlatformViewGL::GLContextFBO() const {
+intptr_t ShellTestPlatformViewGL::GLContextFBO(GLFrameInfo frame_info) const {
   return gl_surface_.GetFramebuffer();
 }
 

shell/common/shell_test_platform_view_gl.h

@@ -56,7 +56,7 @@ class ShellTestPlatformViewGL : public ShellTestPlatformView,
   bool GLContextPresent() override;
 
   // |GPUSurfaceGLDelegate|
-  intptr_t GLContextFBO() const override;
+  intptr_t GLContextFBO(GLFrameInfo frame_info) const override;
 
   // |GPUSurfaceGLDelegate|
   GLProcResolver GetGLProcResolver() const override;

shell/gpu/gpu_surface_gl.cc

@@ -204,10 +204,12 @@ bool GPUSurfaceGL::CreateOrUpdateSurfaces(const SkISize& size) {
 
   sk_sp<SkSurface> onscreen_surface;
 
+  GLFrameInfo frame_info = {static_cast<uint32_t>(size.width()),
+                            static_cast<uint32_t>(size.height())};
   onscreen_surface =
-      WrapOnscreenSurface(context_.get(),            // GL context
-                          size,                      // root surface size
-                          delegate_->GLContextFBO()  // window FBO ID
+      WrapOnscreenSurface(context_.get(),  // GL context
+                          size,            // root surface size
+                          delegate_->GLContextFBO(frame_info)  // window FBO ID
       );
 
   if (onscreen_surface == nullptr) {
@@ -287,13 +289,16 @@ bool GPUSurfaceGL::PresentSurface(SkCanvas* canvas) {
     auto current_size =
         SkISize::Make(onscreen_surface_->width(), onscreen_surface_->height());
 
+    GLFrameInfo frame_info = {static_cast<uint32_t>(current_size.width()),
+                              static_cast<uint32_t>(current_size.height())};
+
     // The FBO has changed, ask the delegate for the new FBO and do a surface
     // re-wrap.
-    auto new_onscreen_surface =
-        WrapOnscreenSurface(context_.get(),            // GL context
-                            current_size,              // root surface size
-                            delegate_->GLContextFBO()  // window FBO ID
-        );
+    auto new_onscreen_surface = WrapOnscreenSurface(
+        context_.get(),                      // GL context
+        current_size,                        // root surface size
+        delegate_->GLContextFBO(frame_info)  // window FBO ID
+    );
 
     if (!new_onscreen_surface) {
       return false;

shell/gpu/gpu_surface_gl_delegate.h

@@ -14,6 +14,13 @@
 
 namespace flutter {
 
+// A structure to represent the frame information which is passed to the
+// embedder when requesting a frame buffer object.
+struct GLFrameInfo {
+  uint32_t width;
+  uint32_t height;
+};
+
 class GPUSurfaceGLDelegate : public GPUSurfaceDelegate {
  public:
   ~GPUSurfaceGLDelegate() override;
@@ -33,13 +40,13 @@ class GPUSurfaceGLDelegate : public GPUSurfaceDelegate {
   virtual bool GLContextPresent() = 0;
 
   // The ID of the main window bound framebuffer. Typically FBO0.
-  virtual intptr_t GLContextFBO() const = 0;
+  virtual intptr_t GLContextFBO(GLFrameInfo frame_info) const = 0;
 
   // The rendering subsystem assumes that the ID of the main window bound
   // framebuffer remains constant throughout. If this assumption in incorrect,
   // embedders are required to return true from this method. In such cases,
-  // GLContextFBO() will be called again to acquire the new FBO ID for rendering
-  // subsequent frames.
+  // GLContextFBO(frame_info) will be called again to acquire the new FBO ID for
+  // rendering subsequent frames.
   virtual bool GLContextFBOResetAfterPresent() const;
 
   // Indicates whether or not the surface supports pixel readback as used in

shell/platform/android/android_surface_gl.cc

@@ -115,7 +115,7 @@ bool AndroidSurfaceGL::GLContextPresent() {
   return onscreen_surface_->SwapBuffers();
 }
 
-intptr_t AndroidSurfaceGL::GLContextFBO() const {
+intptr_t AndroidSurfaceGL::GLContextFBO(GLFrameInfo frame_info) const {
   FML_DCHECK(IsValid());
   // The default window bound framebuffer on Android.
   return 0;

shell/platform/android/android_surface_gl.h

@@ -59,7 +59,7 @@ class AndroidSurfaceGL final : public GPUSurfaceGLDelegate,
   bool GLContextPresent() override;
 
   // |GPUSurfaceGLDelegate|
-  intptr_t GLContextFBO() const override;
+  intptr_t GLContextFBO(GLFrameInfo frame_info) const override;
 
   // |GPUSurfaceGLDelegate|
   ExternalViewEmbedder* GetExternalViewEmbedder() override;

shell/platform/android/surface/android_surface_mock.cc

@@ -18,7 +18,7 @@ bool AndroidSurfaceMock::GLContextPresent() {
   return true;
 }
 
-intptr_t AndroidSurfaceMock::GLContextFBO() const {
+intptr_t AndroidSurfaceMock::GLContextFBO(GLFrameInfo frame_info) const {
   return 0;
 }
 

shell/platform/android/surface/android_surface_mock.h

@@ -48,7 +48,7 @@ class AndroidSurfaceMock final : public GPUSurfaceGLDelegate,
   bool GLContextPresent() override;
 
   // |GPUSurfaceGLDelegate|
-  intptr_t GLContextFBO() const override;
+  intptr_t GLContextFBO(GLFrameInfo frame_info) const override;
 
   // |GPUSurfaceGLDelegate|
   ExternalViewEmbedder* GetExternalViewEmbedder() override;

shell/platform/darwin/ios/ios_surface_gl.h

@@ -43,7 +43,7 @@ class IOSSurfaceGL final : public IOSSurface, public GPUSurfaceGLDelegate {
   bool GLContextPresent() override;
 
   // |GPUSurfaceGLDelegate|
-  intptr_t GLContextFBO() const override;
+  intptr_t GLContextFBO(GLFrameInfo frame_info) const override;
 
   // |GPUSurfaceGLDelegate|
   bool SurfaceSupportsReadback() const override;

shell/platform/darwin/ios/ios_surface_gl.mm

@@ -44,7 +44,7 @@
 }
 
 // |GPUSurfaceGLDelegate|
-intptr_t IOSSurfaceGL::GLContextFBO() const {
+intptr_t IOSSurfaceGL::GLContextFBO(GLFrameInfo frame_info) const {
   return IsValid() ? render_target_->GetFramebuffer() : GL_NONE;
 }
 

shell/platform/embedder/embedder.cc

@@ -93,8 +93,17 @@ static bool IsOpenGLRendererConfigValid(const FlutterRendererConfig* config) {
 
   if (SAFE_ACCESS(open_gl_config, make_current, nullptr) == nullptr ||
       SAFE_ACCESS(open_gl_config, clear_current, nullptr) == nullptr ||
-      SAFE_ACCESS(open_gl_config, present, nullptr) == nullptr ||
-      SAFE_ACCESS(open_gl_config, fbo_callback, nullptr) == nullptr) {
+      SAFE_ACCESS(open_gl_config, present, nullptr) == nullptr) {
+    return false;
+  }
+
+  bool fbo_callback_exists =
+      SAFE_ACCESS(open_gl_config, fbo_callback, nullptr) != nullptr;
+  bool fbo_with_frame_info_callback_exists =
+      SAFE_ACCESS(open_gl_config, fbo_with_frame_info_callback, nullptr) !=
+      nullptr;
+  // only one of these callbacks must exist.
+  if (fbo_callback_exists == fbo_with_frame_info_callback_exists) {
     return false;
   }
 
@@ -168,8 +177,20 @@ InferOpenGLPlatformViewCreationCallback(
     return ptr(user_data);
   };
 
-  auto gl_fbo_callback = [ptr = config->open_gl.fbo_callback,
-                          user_data]() -> intptr_t { return ptr(user_data); };
+  auto gl_fbo_callback =
+      [fbo_callback = config->open_gl.fbo_callback,
+       fbo_with_frame_info_callback =
+           config->open_gl.fbo_with_frame_info_callback,
+       user_data](flutter::GLFrameInfo gl_frame_info) -> intptr_t {
+    if (fbo_callback) {
+      return fbo_callback(user_data);
+    } else {
+      FlutterFrameInfo frame_info = {};
+      frame_info.struct_size = sizeof(FlutterFrameInfo);
+      frame_info.size = {gl_frame_info.width, gl_frame_info.height};
+      return fbo_with_frame_info_callback(user_data, &frame_info);
+    }
+  };
 
   const FlutterOpenGLRendererConfig* open_gl_config = &config->open_gl;
   std::function<bool()> gl_make_resource_current_callback = nullptr;

shell/platform/embedder/embedder.h

@@ -306,12 +306,46 @@ typedef bool (*TextureFrameCallback)(void* /* user data */,
                                      FlutterOpenGLTexture* /* texture out */);
 typedef void (*VsyncCallback)(void* /* user data */, intptr_t /* baton */);
 
+/// A structure to represent the width and height.
+typedef struct {
+  double width;
+  double height;
+} FlutterSize;
+
+/// A structure to represent the width and height.
+///
+/// See: \ref FlutterSize when the value are not integers.
+typedef struct {
+  uint32_t width;
+  uint32_t height;
+} FlutterUIntSize;
+
+/// This information is passed to the embedder when requesting a frame buffer
+/// object.
+///
+/// See: \ref FlutterSoftwareRendererConfig.fbo_with_frame_info_callback.
+typedef struct {
+  /// The size of this struct. Must be sizeof(FlutterFrameInfo).
+  size_t struct_size;
+  /// The size of the surface that will be backed by the fbo.
+  FlutterUIntSize size;
+} FlutterFrameInfo;
+
+typedef uint32_t (*UIntFrameInfoCallback)(
+    void* /* user data */,
+    const FlutterFrameInfo* /* frame info */);
+
 typedef struct {
   /// The size of this struct. Must be sizeof(FlutterOpenGLRendererConfig).
   size_t struct_size;
   BoolCallback make_current;
   BoolCallback clear_current;
   BoolCallback present;
+  /// Specifying one (and only one) of the `fbo_callback` or
+  /// `fbo_with_frame_info_callback` is required. Specifying both is an error
+  /// and engine intialization will be terminated. The return value indicates
+  /// the id of the frame buffer object that flutter will obtain the gl surface
+  /// from.
   UIntCallback fbo_callback;
   /// This is an optional callback. Flutter will ask the emebdder to create a GL
   /// context current on a background thread. If the embedder is able to do so,
@@ -342,6 +376,14 @@ typedef struct {
   /// that external texture details can be supplied to the engine for subsequent
   /// composition.
   TextureFrameCallback gl_external_texture_frame_callback;
+  /// Specifying one (and only one) of the `fbo_callback` or
+  /// `fbo_with_frame_info_callback` is required. Specifying both is an error
+  /// and engine intialization will be terminated. The return value indicates
+  /// the id of the frame buffer object (fbo) that flutter will obtain the gl
+  /// surface from. When using this variant, the embedder is passed a
+  /// `FlutterFrameInfo` struct that indicates the properties of the surface
+  /// that flutter will acquire from the returned fbo.
+  UIntFrameInfoCallback fbo_with_frame_info_callback;
 } FlutterOpenGLRendererConfig;
 
 typedef struct {
@@ -502,11 +544,6 @@ typedef struct {
   double y;
 } FlutterPoint;
 
-typedef struct {
-  double width;
-  double height;
-} FlutterSize;
-
 typedef struct {
   FlutterRect rect;
   FlutterSize upper_left_corner_radius;

shell/platform/embedder/embedder_surface_gl.cc

@@ -50,8 +50,8 @@ bool EmbedderSurfaceGL::GLContextPresent() {
 }
 
 // |GPUSurfaceGLDelegate|
-intptr_t EmbedderSurfaceGL::GLContextFBO() const {
-  return gl_dispatch_table_.gl_fbo_callback();
+intptr_t EmbedderSurfaceGL::GLContextFBO(GLFrameInfo frame_info) const {
+  return gl_dispatch_table_.gl_fbo_callback(frame_info);
 }
 
 // |GPUSurfaceGLDelegate|

shell/platform/embedder/embedder_surface_gl.h

@@ -19,7 +19,7 @@ class EmbedderSurfaceGL final : public EmbedderSurface,
     std::function<bool(void)> gl_make_current_callback;           // required
     std::function<bool(void)> gl_clear_current_callback;          // required
     std::function<bool(void)> gl_present_callback;                // required
-    std::function<intptr_t(void)> gl_fbo_callback;                // required
+    std::function<intptr_t(GLFrameInfo)> gl_fbo_callback;         // required
     std::function<bool(void)> gl_make_resource_current_callback;  // optional
     std::function<SkMatrix(void)>
         gl_surface_transformation_callback;              // optional
@@ -59,7 +59,7 @@ class EmbedderSurfaceGL final : public EmbedderSurface,
   bool GLContextPresent() override;
 
   // |GPUSurfaceGLDelegate|
-  intptr_t GLContextFBO() const override;
+  intptr_t GLContextFBO(GLFrameInfo frame_info) const override;
 
   // |GPUSurfaceGLDelegate|
   bool GLContextFBOResetAfterPresent() const override;

shell/platform/embedder/tests/embedder_config_builder.cc

@@ -35,8 +35,10 @@ EmbedderConfigBuilder::EmbedderConfigBuilder(
   opengl_renderer_config_.present = [](void* context) -> bool {
     return reinterpret_cast<EmbedderTestContext*>(context)->GLPresent();
   };
-  opengl_renderer_config_.fbo_callback = [](void* context) -> uint32_t {
-    return reinterpret_cast<EmbedderTestContext*>(context)->GLGetFramebuffer();
+  opengl_renderer_config_.fbo_with_frame_info_callback =
+      [](void* context, const FlutterFrameInfo* frame_info) -> uint32_t {
+    return reinterpret_cast<EmbedderTestContext*>(context)->GLGetFramebuffer(
+        *frame_info);
   };
   opengl_renderer_config_.make_resource_current = [](void* context) -> bool {
     return reinterpret_cast<EmbedderTestContext*>(context)
@@ -110,6 +112,21 @@ void EmbedderConfigBuilder::SetSoftwareRendererConfig(SkISize surface_size) {
   context_.SetupOpenGLSurface(surface_size);
 }
 
+void EmbedderConfigBuilder::SetOpenGLFBOCallBack() {
+  // SetOpenGLRendererConfig must be called before this.
+  FML_CHECK(renderer_config_.type == FlutterRendererType::kOpenGL);
+  renderer_config_.open_gl.fbo_callback = [](void* context) -> uint32_t {
+    FlutterFrameInfo frame_info = {};
+    // fbo_callback doesn't use the frame size information, only
+    // fbo_callback_with_frame_info does.
+    frame_info.struct_size = sizeof(FlutterFrameInfo);
+    frame_info.size.width = 0;
+    frame_info.size.height = 0;
+    return reinterpret_cast<EmbedderTestContext*>(context)->GLGetFramebuffer(
+        frame_info);
+  };
+}
+
 void EmbedderConfigBuilder::SetOpenGLRendererConfig(SkISize surface_size) {
   renderer_config_.type = FlutterRendererType::kOpenGL;
   renderer_config_.open_gl = opengl_renderer_config_;

shell/platform/embedder/tests/embedder_config_builder.h

@@ -49,6 +49,12 @@ class EmbedderConfigBuilder {
 
   void SetOpenGLRendererConfig(SkISize surface_size);
 
+  // Used to explicitly set an `open_gl.fbo_callback`. Using this method will
+  // cause your test to fail since the ctor for this class sets
+  // `open_gl.fbo_callback_with_frame_info`. This method exists as a utility to
+  // explicitly test this behavior.
+  void SetOpenGLFBOCallBack();
+
   void SetAssetsPath();
 
   void SetSnapshots();

shell/platform/embedder/tests/embedder_test_context.cc

@@ -197,11 +197,16 @@ bool EmbedderTestContext::GLPresent() {
   return true;
 }
 
-uint32_t EmbedderTestContext::GLGetFramebuffer() {
+uint32_t EmbedderTestContext::GLGetFramebuffer(FlutterFrameInfo frame_info) {
   FML_CHECK(gl_surface_) << "GL surface must be initialized.";
+  gl_surface_fbo_frame_infos_.push_back(frame_info);
   return gl_surface_->GetFramebuffer();
 }
 
+std::vector<FlutterFrameInfo> EmbedderTestContext::GetGLFBOFrameInfos() {
+  return gl_surface_fbo_frame_infos_;
+}
+
 bool EmbedderTestContext::GLMakeResourceCurrent() {
   FML_CHECK(gl_surface_) << "GL surface must be initialized.";
   return gl_surface_->MakeResourceCurrent();

shell/platform/embedder/tests/embedder_test_context.h

@@ -79,6 +79,9 @@ class EmbedderTestContext {
 
   size_t GetSoftwareSurfacePresentCount() const;
 
+  // Returns the frame information for all the frames that were rendered.
+  std::vector<FlutterFrameInfo> GetGLFBOFrameInfos();
+
  private:
   // This allows the builder to access the hooks.
   friend class EmbedderConfigBuilder;
@@ -101,6 +104,7 @@ class EmbedderTestContext {
   std::unique_ptr<EmbedderTestCompositor> compositor_;
   NextSceneCallback next_scene_callback_;
   SkMatrix root_surface_transformation_;
+  std::vector<FlutterFrameInfo> gl_surface_fbo_frame_infos_;
   size_t gl_surface_present_count_ = 0;
   size_t software_surface_present_count_ = 0;
 
@@ -133,7 +137,7 @@ class EmbedderTestContext {
 
   bool GLPresent();
 
-  uint32_t GLGetFramebuffer();
+  uint32_t GLGetFramebuffer(FlutterFrameInfo frame_info);
 
   bool GLMakeResourceCurrent();