Update embedder support for Impeller/OpenGL to load some missing shaders and configure a depth attachment (flutter/engine#50416)

engine/src/flutter/impeller/renderer/backend/gles/buffer_bindings_gles.cc

@@ -15,6 +15,11 @@
 
 namespace impeller {
 
+// This prefix is used in the names of inputs generated by ANGLE's framebuffer
+// fetch emulation.
+static constexpr std::string_view kAngleInputAttachmentPrefix =
+    "ANGLEInputAttachment";
+
 BufferBindingsGLES::BufferBindingsGLES() = default;
 
 BufferBindingsGLES::~BufferBindingsGLES() = default;
@@ -110,6 +115,17 @@ bool BufferBindingsGLES::ReadUniformsBindings(const ProcTableGLES& gl,
                         &uniform_type,      // type
                         name.data()         // name
     );
+
+    // Skip unrecognized variables generated by ANGLE.
+    if (gl.GetCapabilities()->IsANGLE()) {
+      if (written_count >=
+              static_cast<GLsizei>(kAngleInputAttachmentPrefix.length()) &&
+          std::string_view(name.data(), kAngleInputAttachmentPrefix.length()) ==
+              kAngleInputAttachmentPrefix) {
+        continue;
+      }
+    }
+
     auto location = gl.GetUniformLocation(program, name.data());
     if (location == -1) {
       VALIDATION_LOG << "Could not query the location of an active uniform.";

engine/src/flutter/impeller/renderer/backend/gles/capabilities_gles.cc

@@ -117,6 +117,8 @@ CapabilitiesGLES::CapabilitiesGLES(const ProcTableGLES& gl) {
     gl.GetIntegerv(GL_MAX_SAMPLES_EXT, &value);
     supports_offscreen_msaa_ = value >= 4;
   }
+
+  is_angle_ = desc->IsANGLE();
 }
 
 size_t CapabilitiesGLES::GetMaxTextureUnits(ShaderStage stage) const {
@@ -188,4 +190,8 @@ PixelFormat CapabilitiesGLES::GetDefaultDepthStencilFormat() const {
   return PixelFormat::kD24UnormS8Uint;
 }
 
+bool CapabilitiesGLES::IsANGLE() const {
+  return is_angle_;
+}
+
 }  // namespace impeller

engine/src/flutter/impeller/renderer/backend/gles/capabilities_gles.h

@@ -74,6 +74,8 @@ class CapabilitiesGLES final
 
   size_t GetMaxTextureUnits(ShaderStage stage) const;
 
+  bool IsANGLE() const;
+
   // |Capabilities|
   bool SupportsOffscreenMSAA() const override;
 
@@ -121,6 +123,7 @@ class CapabilitiesGLES final
   bool supports_decal_sampler_address_mode_ = false;
   bool supports_offscreen_msaa_ = false;
   bool supports_implicit_msaa_ = false;
+  bool is_angle_ = false;
 };
 
 }  // namespace impeller

engine/src/flutter/impeller/renderer/backend/gles/description_gles.cc

@@ -40,6 +40,10 @@ static bool DetermineIfES(const std::string& version) {
   return HasPrefix(version, "OpenGL ES");
 }
 
+static bool DetermineIfANGLE(const std::string& version) {
+  return version.find("ANGLE") != std::string::npos;
+}
+
 static std::optional<Version> DetermineVersion(std::string version) {
   // Format for OpenGL "OpenGL<space>ES<space><version
   // number><space><vendor-specific information>".
@@ -81,6 +85,7 @@ DescriptionGLES::DescriptionGLES(const ProcTableGLES& gl)
       gl_version_string_(GetGLString(gl, GL_VERSION)),
       sl_version_string_(GetGLString(gl, GL_SHADING_LANGUAGE_VERSION)) {
   is_es_ = DetermineIfES(gl_version_string_);
+  is_angle_ = DetermineIfANGLE(gl_version_string_);
 
   auto gl_version = DetermineVersion(gl_version_string_);
   if (!gl_version.has_value()) {
@@ -164,6 +169,10 @@ bool DescriptionGLES::IsES() const {
   return is_es_;
 }
 
+bool DescriptionGLES::IsANGLE() const {
+  return is_angle_;
+}
+
 bool DescriptionGLES::HasExtension(const std::string& ext) const {
   return extensions_.find(ext) != extensions_.end();
 }

engine/src/flutter/impeller/renderer/backend/gles/description_gles.h

@@ -34,6 +34,8 @@ class DescriptionGLES {
   /// @brief      Returns whether GLES includes the debug extension.
   bool HasDebugExtension() const;
 
+  bool IsANGLE() const;
+
  private:
   Version gl_version_;
   Version sl_version_;
@@ -43,6 +45,7 @@ class DescriptionGLES {
   std::string gl_version_string_;
   std::string sl_version_string_;
   std::set<std::string> extensions_;
+  bool is_angle_ = false;
   bool is_valid_ = false;
 
   DescriptionGLES(const DescriptionGLES&) = delete;

engine/src/flutter/impeller/renderer/backend/gles/render_pass_gles.cc

@@ -473,23 +473,21 @@ struct RenderPassData {
   if (gl.DiscardFramebufferEXT.IsAvailable()) {
     std::vector<GLenum> attachments;
 
+    // TODO(jonahwilliams): discarding stencil or depth on the default fbo
+    // causes Angle to discard the entire render target. Until we know the
+    // reason, default to storing.
+    bool angle_safe = gl.GetCapabilities()->IsANGLE() ? !is_default_fbo : true;
+
     if (pass_data.discard_color_attachment) {
       attachments.push_back(is_default_fbo ? GL_COLOR_EXT
                                            : GL_COLOR_ATTACHMENT0);
     }
-    if (pass_data.discard_depth_attachment) {
+    if (pass_data.discard_depth_attachment && angle_safe) {
       attachments.push_back(is_default_fbo ? GL_DEPTH_EXT
                                            : GL_DEPTH_ATTACHMENT);
     }
 
-// TODO(jonahwilliams): discarding the stencil on the default fbo when running
-// on Windows causes Angle to discard the entire render target. Until we know
-// the reason, default to storing.
-#ifdef FML_OS_WIN
-    if (pass_data.discard_stencil_attachment && !is_default_fbo) {
-#else
-    if (pass_data.discard_stencil_attachment) {
-#endif
+    if (pass_data.discard_stencil_attachment && angle_safe) {
       attachments.push_back(is_default_fbo ? GL_STENCIL_EXT
                                            : GL_STENCIL_ATTACHMENT);
     }

engine/src/flutter/shell/platform/embedder/BUILD.gn

@@ -250,6 +250,7 @@ test_fixtures("fixtures") {
     "fixtures/scene_without_custom_compositor.png",
     "fixtures/scene_without_custom_compositor_with_xform.png",
     "fixtures/snapshot_large_scene.png",
+    "fixtures/solid_red.png",
     "fixtures/verifyb143464703.png",
     "fixtures/verifyb143464703_soft_noxform.png",
   ]

engine/src/flutter/shell/platform/embedder/embedder.cc

@@ -310,22 +310,27 @@ InferOpenGLPlatformViewCreationCallback(
       // damage are always 1. Once the function that computes damage implements
       // support for multiple damage rectangles, GLPresentInfo should also
       // contain the number of damage rectangles.
-      const size_t num_rects = 1;
 
-      std::array<FlutterRect, num_rects> frame_damage_rect = {
-          SkIRectToFlutterRect(*(gl_present_info.frame_damage))};
-      std::array<FlutterRect, num_rects> buffer_damage_rect = {
-          SkIRectToFlutterRect(*(gl_present_info.buffer_damage))};
+      std::optional<FlutterRect> frame_damage_rect;
+      if (gl_present_info.frame_damage) {
+        frame_damage_rect =
+            SkIRectToFlutterRect(*(gl_present_info.frame_damage));
+      }
+      std::optional<FlutterRect> buffer_damage_rect;
+      if (gl_present_info.buffer_damage) {
+        buffer_damage_rect =
+            SkIRectToFlutterRect(*(gl_present_info.buffer_damage));
+      }
 
       FlutterDamage frame_damage{
           .struct_size = sizeof(FlutterDamage),
-          .num_rects = frame_damage_rect.size(),
-          .damage = frame_damage_rect.data(),
+          .num_rects = frame_damage_rect ? size_t{1} : size_t{0},
+          .damage = frame_damage_rect ? &frame_damage_rect.value() : nullptr,
       };
       FlutterDamage buffer_damage{
           .struct_size = sizeof(FlutterDamage),
-          .num_rects = buffer_damage_rect.size(),
-          .damage = buffer_damage_rect.data(),
+          .num_rects = buffer_damage_rect ? size_t{1} : size_t{0},
+          .damage = buffer_damage_rect ? &buffer_damage_rect.value() : nullptr,
       };
 
       // Construct the present information concerning the frame being rendered.
@@ -981,31 +986,44 @@ MakeRenderTargetFromBackingStoreImpeller(
   color0.load_action = impeller::LoadAction::kClear;
   color0.store_action = impeller::StoreAction::kStore;
 
-  impeller::TextureDescriptor stencil0_tex;
-  stencil0_tex.type = impeller::TextureType::kTexture2D;
-  stencil0_tex.format = impeller::PixelFormat::kR8G8B8A8UNormInt;
-  stencil0_tex.size = size;
-  stencil0_tex.usage = static_cast<impeller::TextureUsageMask>(
+  impeller::TextureDescriptor depth_stencil_texture_desc;
+  depth_stencil_texture_desc.type = impeller::TextureType::kTexture2D;
+  depth_stencil_texture_desc.format = impeller::PixelFormat::kR8G8B8A8UNormInt;
+  depth_stencil_texture_desc.size = size;
+  depth_stencil_texture_desc.usage = static_cast<impeller::TextureUsageMask>(
       impeller::TextureUsage::kRenderTarget);
-  stencil0_tex.sample_count = impeller::SampleCount::kCount1;
+  depth_stencil_texture_desc.sample_count = impeller::SampleCount::kCount1;
+
+  auto depth_stencil_tex = std::make_shared<impeller::TextureGLES>(
+      gl_context.GetReactor(), depth_stencil_texture_desc,
+      impeller::TextureGLES::IsWrapped::kWrapped);
+
+  impeller::DepthAttachment depth0;
+  depth0.clear_depth = 0;
+  depth0.texture = depth_stencil_tex;
+  depth0.load_action = impeller::LoadAction::kClear;
+  depth0.store_action = impeller::StoreAction::kDontCare;
 
   impeller::StencilAttachment stencil0;
   stencil0.clear_stencil = 0;
-  stencil0.texture = std::make_shared<impeller::TextureGLES>(
-      gl_context.GetReactor(), stencil0_tex,
-      impeller::TextureGLES::IsWrapped::kWrapped);
+  stencil0.texture = depth_stencil_tex;
   stencil0.load_action = impeller::LoadAction::kClear;
   stencil0.store_action = impeller::StoreAction::kDontCare;
 
   impeller::RenderTarget render_target_desc;
 
   render_target_desc.SetColorAttachment(color0, 0u);
+  render_target_desc.SetDepthAttachment(depth0);
   render_target_desc.SetStencilAttachment(stencil0);
 
+  fml::closure framebuffer_destruct =
+      [callback = framebuffer->destruction_callback,
+       user_data = framebuffer->user_data]() { callback(user_data); };
+
   return std::make_unique<flutter::EmbedderRenderTargetImpeller>(
       backing_store, aiks_context,
       std::make_unique<impeller::RenderTarget>(std::move(render_target_desc)),
-      on_release);
+      on_release, framebuffer_destruct);
 #else
   return nullptr;
 #endif
@@ -1075,7 +1093,7 @@ MakeRenderTargetFromBackingStoreImpeller(
   return std::make_unique<flutter::EmbedderRenderTargetImpeller>(
       backing_store, aiks_context,
       std::make_unique<impeller::RenderTarget>(std::move(render_target_desc)),
-      on_release);
+      on_release, fml::closure());
 #else
   return nullptr;
 #endif

engine/src/flutter/shell/platform/embedder/embedder_render_target_impeller.cc

@@ -13,15 +13,22 @@ EmbedderRenderTargetImpeller::EmbedderRenderTargetImpeller(
     FlutterBackingStore backing_store,
     std::shared_ptr<impeller::AiksContext> aiks_context,
     std::unique_ptr<impeller::RenderTarget> impeller_target,
-    fml::closure on_release)
+    fml::closure on_release,
+    fml::closure framebuffer_destruction_callback)
     : EmbedderRenderTarget(backing_store, std::move(on_release)),
       aiks_context_(std::move(aiks_context)),
-      impeller_target_(std::move(impeller_target)) {
+      impeller_target_(std::move(impeller_target)),
+      framebuffer_destruction_callback_(
+          std::move(framebuffer_destruction_callback)) {
   FML_DCHECK(aiks_context_);
   FML_DCHECK(impeller_target_);
 }
 
-EmbedderRenderTargetImpeller::~EmbedderRenderTargetImpeller() = default;
+EmbedderRenderTargetImpeller::~EmbedderRenderTargetImpeller() {
+  if (framebuffer_destruction_callback_) {
+    framebuffer_destruction_callback_();
+  }
+}
 
 sk_sp<SkSurface> EmbedderRenderTargetImpeller::GetSkiaSurface() const {
   return nullptr;

engine/src/flutter/shell/platform/embedder/embedder_render_target_impeller.h

@@ -15,7 +15,8 @@ class EmbedderRenderTargetImpeller final : public EmbedderRenderTarget {
       FlutterBackingStore backing_store,
       std::shared_ptr<impeller::AiksContext> aiks_context,
       std::unique_ptr<impeller::RenderTarget> impeller_target,
-      fml::closure on_release);
+      fml::closure on_release,
+      fml::closure framebuffer_destruction_callback);
 
   // |EmbedderRenderTarget|
   ~EmbedderRenderTargetImpeller() override;
@@ -35,6 +36,7 @@ class EmbedderRenderTargetImpeller final : public EmbedderRenderTarget {
  private:
   std::shared_ptr<impeller::AiksContext> aiks_context_;
   std::unique_ptr<impeller::RenderTarget> impeller_target_;
+  fml::closure framebuffer_destruction_callback_;
 
   FML_DISALLOW_COPY_AND_ASSIGN(EmbedderRenderTargetImpeller);
 };

engine/src/flutter/shell/platform/embedder/embedder_surface_gl_impeller.cc

@@ -7,6 +7,8 @@
 #include <utility>
 
 #include "impeller/entity/gles/entity_shaders_gles.h"
+#include "impeller/entity/gles/framebuffer_blend_shaders_gles.h"
+#include "impeller/entity/gles/modern_shaders_gles.h"
 #include "impeller/renderer/backend/gles/context_gles.h"
 #include "impeller/renderer/backend/gles/proc_table_gles.h"
 
@@ -68,6 +70,12 @@ EmbedderSurfaceGLImpeller::EmbedderSurfaceGLImpeller(
       std::make_shared<fml::NonOwnedMapping>(
           impeller_entity_shaders_gles_data,
           impeller_entity_shaders_gles_length),
+      std::make_shared<fml::NonOwnedMapping>(
+          impeller_modern_shaders_gles_data,
+          impeller_modern_shaders_gles_length),
+      std::make_shared<fml::NonOwnedMapping>(
+          impeller_framebuffer_blend_shaders_gles_data,
+          impeller_framebuffer_blend_shaders_gles_length),
 #if IMPELLER_ENABLE_3D
       std::make_shared<fml::NonOwnedMapping>(
           impeller_scene_shaders_gles_data, impeller_scene_shaders_gles_length),

engine/src/flutter/shell/platform/embedder/tests/embedder_gl_unittests.cc

@@ -26,6 +26,7 @@
 #include "flutter/fml/thread.h"
 #include "flutter/lib/ui/painting/image.h"
 #include "flutter/runtime/dart_vm.h"
+#include "flutter/shell/platform/embedder/embedder_surface_gl_impeller.h"
 #include "flutter/shell/platform/embedder/tests/embedder_assertions.h"
 #include "flutter/shell/platform/embedder/tests/embedder_config_builder.h"
 #include "flutter/shell/platform/embedder/tests/embedder_test.h"
@@ -4699,6 +4700,37 @@ TEST_F(EmbedderTest,
   latch.Wait();
 }
 
+TEST_F(EmbedderTest, CanRenderWithImpellerOpenGL) {
+  auto& context = GetEmbedderContext(EmbedderTestContextType::kOpenGLContext);
+  EmbedderConfigBuilder builder(context);
+
+  builder.AddCommandLineArgument("--enable-impeller");
+  builder.SetDartEntrypoint("draw_solid_red");
+  builder.SetOpenGLRendererConfig(SkISize::Make(800, 600));
+  builder.SetCompositor();
+  builder.SetRenderTargetType(
+      EmbedderTestBackingStoreProducer::RenderTargetType::kOpenGLFramebuffer);
+
+  auto rendered_scene = context.GetNextSceneImage();
+
+  auto engine = builder.LaunchEngine();
+  ASSERT_TRUE(engine.is_valid());
+
+  // Send a window metrics events so frames may be scheduled.
+  FlutterWindowMetricsEvent event = {};
+  event.struct_size = sizeof(event);
+  event.width = 800;
+  event.height = 600;
+  event.pixel_ratio = 1.0;
+  ASSERT_EQ(FlutterEngineSendWindowMetricsEvent(engine.get(), &event),
+            kSuccess);
+
+  ASSERT_TRUE(ImageMatchesFixture(
+      FixtureNameForBackend(EmbedderTestContextType::kOpenGLContext,
+                            "solid_red.png"),
+      rendered_scene));
+}
+
 INSTANTIATE_TEST_SUITE_P(
     EmbedderTestGlVk,
     EmbedderTestMultiBackend,