[CP][Impeller] Fix crash when using BackdropFilters in certain GLES drivers. (#163581)

This is a cherry picked of https://github.com/flutter/flutter/pull/163345 and https://github.com/flutter/flutter/pull/163327 combined, as they both are parts of the same bug.

The issues are:
  https://github.com/flutter/flutter/issues/163304
  https://github.com/flutter/flutter/issues/163421
  
And potentially others, though we don't have clear repros or stack traces for all of them.

CHANGELOG.md

@@ -30,6 +30,7 @@ INTERNAL NOTE
 ### [3.29.0](https://github.com/flutter/flutter/releases/tag/3.29.0)
 Initial stable release.
 
+- [flutter/163304](https://github.com/flutter/flutter/issues/163304) Fixes crash when using backdrop filter on GLES backend.
 - [flutter/161334](https://github.com/flutter/flutter/issues/161334) Disable Vulkan on certain Xclipse GPU models.
 
 ## Flutter 3.27 Changes

engine/src/flutter/impeller/display_list/canvas.cc

@@ -1677,6 +1677,14 @@ std::shared_ptr<Texture> Canvas::FlipBackdrop(Point global_pass_position,
   return input_texture;
 }
 
+bool Canvas::SupportsBlitToOnscreen() const {
+  return renderer_.GetContext()
+             ->GetCapabilities()
+             ->SupportsTextureToTextureBlits() &&
+         renderer_.GetContext()->GetBackendType() !=
+             Context::BackendType::kOpenGLES;
+}
+
 bool Canvas::BlitToOnscreen(bool is_onscreen) {
   auto command_buffer = renderer_.GetContext()->CreateCommandBuffer();
   command_buffer->SetLabel("EntityPass Root Command Buffer");
@@ -1684,9 +1692,7 @@ bool Canvas::BlitToOnscreen(bool is_onscreen) {
                               .inline_pass_context->GetPassTarget()
                               .GetRenderTarget();
 
-  if (renderer_.GetContext()
-          ->GetCapabilities()
-          ->SupportsTextureToTextureBlits()) {
+  if (SupportsBlitToOnscreen()) {
     auto blit_pass = command_buffer->CreateBlitPass();
     blit_pass->AddCopy(offscreen_target.GetRenderTargetTexture(),
                        render_target_.GetRenderTargetTexture());

engine/src/flutter/impeller/display_list/canvas.h

@@ -251,6 +251,16 @@ class Canvas {
   // Visible for testing.
   bool RequiresReadback() const { return requires_readback_; }
 
+  // Whether the current device has the capabilities to blit an offscreen
+  // texture into the onscreen.
+  //
+  // This requires the availibility of the blit framebuffer command, but is
+  // disabled for GLES. A simple glBlitFramebuffer does not support resolving
+  // different sample counts which may be present in GLES when using MSAA.
+  //
+  // Visible for testing.
+  bool SupportsBlitToOnscreen() const;
+
  private:
   ContentContext& renderer_;
   RenderTarget render_target_;

engine/src/flutter/impeller/display_list/canvas_unittests.cc

@@ -14,6 +14,7 @@
 #include "impeller/display_list/aiks_unittests.h"
 #include "impeller/display_list/canvas.h"
 #include "impeller/geometry/geometry_asserts.h"
+#include "impeller/playground/playground.h"
 #include "impeller/renderer/render_target.h"
 
 namespace impeller {
@@ -278,5 +279,17 @@ TEST_P(AiksTest, BackdropCountDownWithNestedSaveLayers) {
   EXPECT_TRUE(canvas->RequiresReadback());
 }
 
+TEST_P(AiksTest, SupportsBlitToOnscreen) {
+  ContentContext context(GetContext(), nullptr);
+  auto canvas = CreateTestCanvas(context, Rect::MakeLTRB(0, 0, 100, 100),
+                                 /*requires_readback=*/true);
+
+  if (GetBackend() == PlaygroundBackend::kOpenGLES) {
+    EXPECT_FALSE(canvas->SupportsBlitToOnscreen());
+  } else {
+    EXPECT_TRUE(canvas->SupportsBlitToOnscreen());
+  }
+}
+
 }  // namespace testing
 }  // namespace impeller

engine/src/flutter/impeller/renderer/backend/gles/test/texture_gles_unittests.cc

@@ -65,4 +65,23 @@ TEST_P(TextureGLESTest, CanSetSyncFence) {
   ASSERT_FALSE(sync_fence.has_value());
 }
 
+TEST_P(TextureGLESTest, Binds2DTexture) {
+  TextureDescriptor desc;
+  desc.storage_mode = StorageMode::kDevicePrivate;
+  desc.size = {100, 100};
+  desc.format = PixelFormat::kR8G8B8A8UNormInt;
+  desc.type = TextureType::kTexture2DMultisample;
+  desc.sample_count = SampleCount::kCount4;
+
+  auto texture = GetContext()->GetResourceAllocator()->CreateTexture(desc);
+
+  ASSERT_TRUE(texture);
+
+  EXPECT_EQ(
+      TextureGLES::Cast(*texture).ComputeTypeForBinding(GL_READ_FRAMEBUFFER),
+      TextureGLES::Type::kTexture);
+  EXPECT_EQ(TextureGLES::Cast(*texture).ComputeTypeForBinding(GL_FRAMEBUFFER),
+            TextureGLES::Type::kTextureMultisampled);
+}
+
 }  // namespace impeller::testing

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

@@ -392,6 +392,15 @@ static std::optional<GLenum> ToRenderBufferFormat(PixelFormat format) {
   FML_UNREACHABLE();
 }
 
+TextureGLES::Type TextureGLES::ComputeTypeForBinding(GLenum target) const {
+  // When binding to a GL_READ_FRAMEBUFFER, any multisampled
+  // textures must be bound as single sampled.
+  if (target == GL_READ_FRAMEBUFFER && type_ == Type::kTextureMultisampled) {
+    return Type::kTexture;
+  }
+  return type_;
+}
+
 void TextureGLES::InitializeContentsIfNecessary() const {
   if (!IsValid() || slices_initialized_[0]) {
     return;
@@ -588,7 +597,7 @@ bool TextureGLES::SetAsFramebufferAttachment(
   }
   const auto& gl = reactor_->GetProcTable();
 
-  switch (type_) {
+  switch (ComputeTypeForBinding(target)) {
     case Type::kTexture:
       gl.FramebufferTexture2D(target,                             // target
                               ToAttachmentType(attachment_type),  // attachment

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

@@ -144,6 +144,9 @@ class TextureGLES final : public Texture,
   // Visible for testing.
   std::optional<HandleGLES> GetSyncFence() const;
 
+  // visible for testing
+  Type ComputeTypeForBinding(GLenum target) const;
+
  private:
   std::shared_ptr<ReactorGLES> reactor_;
   const Type type_;