[Impeller] Fix EntityPassTarget::Flip with implict MSAA. (#47701)

This allows backdrop filters to work with GLES and MSAA.

The swap implementation was only swapping out the resolve texture. But with implicit msaa resolve, the resolve texture and msaa texture are the same - so both need to be swapped.

Fixes flutter/flutter#137301

Author: Jonah Williams

ci/licenses_golden/excluded_files

@@ -138,6 +138,7 @@
 ../../../flutter/impeller/entity/contents/filters/inputs/filter_input_unittests.cc
 ../../../flutter/impeller/entity/contents/test
 ../../../flutter/impeller/entity/contents/vertices_contents_unittests.cc
+../../../flutter/impeller/entity/entity_pass_target_unittests.cc
 ../../../flutter/impeller/entity/entity_unittests.cc
 ../../../flutter/impeller/entity/geometry/geometry_unittests.cc
 ../../../flutter/impeller/entity/render_target_cache_unittests.cc

impeller/BUILD.gn

@@ -98,7 +98,6 @@ impeller_component("impeller_unittests") {
       "aiks:aiks_unittests",
       "display_list:display_list_unittests",
       "entity:entity_unittests",
-      "entity:render_target_cache_unittests",
       "fixtures",
       "geometry:geometry_unittests",
       "image:image_unittests",

impeller/core/texture.h

@@ -6,7 +6,6 @@
 
 #include <string_view>
 
-#include "flutter/fml/macros.h"
 #include "flutter/fml/mapping.h"
 #include "impeller/core/formats.h"
 #include "impeller/core/texture_descriptor.h"

impeller/entity/BUILD.gn

@@ -282,10 +282,12 @@ impeller_component("entity_unittests") {
     "contents/checkerboard_contents_unittests.cc",
     "contents/filters/inputs/filter_input_unittests.cc",
     "contents/vertices_contents_unittests.cc",
+    "entity_pass_target_unittests.cc",
     "entity_playground.cc",
     "entity_playground.h",
     "entity_unittests.cc",
     "geometry/geometry_unittests.cc",
+    "render_target_cache_unittests.cc",
   ]
 
   deps = [
@@ -296,14 +298,3 @@ impeller_component("entity_unittests") {
     "//flutter/impeller/typographer/backends/skia:typographer_skia_backend",
   ]
 }
-
-impeller_component("render_target_cache_unittests") {
-  testonly = true
-
-  sources = [ "render_target_cache_unittests.cc" ]
-
-  deps = [
-    ":entity",
-    "//flutter/testing:testing_lib",
-  ]
-}

impeller/entity/entity_pass.cc

@@ -286,7 +286,8 @@ static EntityPassTarget CreateRenderTarget(ContentContext& renderer,
   }
 
   return EntityPassTarget(
-      target, renderer.GetDeviceCapabilities().SupportsReadFromResolve());
+      target, renderer.GetDeviceCapabilities().SupportsReadFromResolve(),
+      renderer.GetDeviceCapabilities().SupportsImplicitResolvingMSAA());
 }
 
 uint32_t EntityPass::GetTotalPassReads(ContentContext& renderer) const {
@@ -397,7 +398,10 @@ bool EntityPass::Render(ContentContext& renderer,
         entity.SetContents(contents);
         entity.SetBlendMode(BlendMode::kSource);
 
-        entity.Render(renderer, *render_pass);
+        if (!entity.Render(renderer, *render_pass)) {
+          VALIDATION_LOG << "Failed to render EntityPass root blit.";
+          return false;
+        }
       }
 
       if (!render_pass->EncodeCommands()) {
@@ -455,7 +459,8 @@ bool EntityPass::Render(ContentContext& renderer,
 
   EntityPassTarget pass_target(
       root_render_target,
-      renderer.GetDeviceCapabilities().SupportsReadFromResolve());
+      renderer.GetDeviceCapabilities().SupportsReadFromResolve(),
+      renderer.GetDeviceCapabilities().SupportsImplicitResolvingMSAA());
 
   return OnRender(                               //
       renderer,                                  // renderer

impeller/entity/entity_pass_target.cc

@@ -11,9 +11,11 @@
 namespace impeller {
 
 EntityPassTarget::EntityPassTarget(const RenderTarget& render_target,
-                                   bool supports_read_from_resolve)
+                                   bool supports_read_from_resolve,
+                                   bool supports_implicit_msaa)
     : target_(render_target),
-      supports_read_from_resolve_(supports_read_from_resolve) {}
+      supports_read_from_resolve_(supports_read_from_resolve),
+      supports_implicit_msaa_(supports_implicit_msaa) {}
 
 std::shared_ptr<Texture> EntityPassTarget::Flip(Allocator& allocator) {
   auto color0 = target_.GetColorAttachments().find(0)->second;
@@ -45,7 +47,16 @@ std::shared_ptr<Texture> EntityPassTarget::Flip(Allocator& allocator) {
     }
   }
 
-  std::swap(color0.resolve_texture, secondary_color_texture_);
+  // If the color0 resolve texture is the same as the texture, then we're
+  // running on the GLES backend with implicit resolve.
+  if (supports_implicit_msaa_) {
+    auto new_secondary = color0.resolve_texture;
+    color0.resolve_texture = secondary_color_texture_;
+    color0.texture = secondary_color_texture_;
+    secondary_color_texture_ = new_secondary;
+  } else {
+    std::swap(color0.resolve_texture, secondary_color_texture_);
+  }
 
   target_.SetColorAttachment(color0, 0);
 

impeller/entity/entity_pass_target.h

@@ -14,7 +14,8 @@ class InlinePassContext;
 class EntityPassTarget {
  public:
   explicit EntityPassTarget(const RenderTarget& render_target,
-                            bool supports_read_from_resolve);
+                            bool supports_read_from_resolve,
+                            bool supports_implicit_msaa);
 
   /// @brief  Flips the backdrop and returns a readable texture that can be
   ///         bound/sampled to restore the previous pass.
@@ -34,6 +35,7 @@ class EntityPassTarget {
   std::shared_ptr<Texture> secondary_color_texture_;
 
   bool supports_read_from_resolve_;
+  bool supports_implicit_msaa_;
 
   friend InlinePassContext;
 

impeller/entity/entity_pass_target_unittests.cc

@@ -0,0 +1,114 @@
+// Copyright 2013 The Flutter Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include <memory>
+
+#include "flutter/testing/testing.h"
+#include "gtest/gtest.h"
+#include "impeller/core/formats.h"
+#include "impeller/entity/entity_pass_target.h"
+#include "impeller/entity/entity_playground.h"
+
+namespace impeller {
+namespace testing {
+
+using EntityPassTargetTest = EntityPlayground;
+INSTANTIATE_PLAYGROUND_SUITE(EntityPassTargetTest);
+
+TEST_P(EntityPassTargetTest, SwapWithMSAATexture) {
+  if (GetContentContext()
+          ->GetDeviceCapabilities()
+          .SupportsImplicitResolvingMSAA()) {
+    GTEST_SKIP() << "Implicit MSAA is used on this device.";
+  }
+  auto content_context = GetContentContext();
+  auto buffer = content_context->GetContext()->CreateCommandBuffer();
+  auto render_target = RenderTarget::CreateOffscreenMSAA(
+      *content_context->GetContext(),
+      *GetContentContext()->GetRenderTargetCache(), {100, 100});
+
+  auto entity_pass_target = EntityPassTarget(render_target, false, false);
+
+  auto color0 = entity_pass_target.GetRenderTarget()
+                    .GetColorAttachments()
+                    .find(0u)
+                    ->second;
+  auto msaa_tex = color0.texture;
+  auto resolve_tex = color0.resolve_texture;
+
+  entity_pass_target.Flip(
+      *content_context->GetContext()->GetResourceAllocator());
+
+  color0 = entity_pass_target.GetRenderTarget()
+               .GetColorAttachments()
+               .find(0u)
+               ->second;
+
+  ASSERT_EQ(msaa_tex, color0.texture);
+  ASSERT_NE(resolve_tex, color0.resolve_texture);
+}
+
+TEST_P(EntityPassTargetTest, SwapWithMSAAImplicitResolve) {
+  auto content_context = GetContentContext();
+  auto buffer = content_context->GetContext()->CreateCommandBuffer();
+  auto context = content_context->GetContext();
+  auto& allocator = *context->GetResourceAllocator();
+
+  // Emulate implicit MSAA resolve by making color resolve and msaa texture the
+  // same.
+  RenderTarget render_target;
+  {
+    PixelFormat pixel_format =
+        context->GetCapabilities()->GetDefaultColorFormat();
+
+    // Create MSAA color texture.
+
+    TextureDescriptor color0_tex_desc;
+    color0_tex_desc.storage_mode = StorageMode::kDevicePrivate;
+    color0_tex_desc.type = TextureType::kTexture2DMultisample;
+    color0_tex_desc.sample_count = SampleCount::kCount4;
+    color0_tex_desc.format = pixel_format;
+    color0_tex_desc.size = ISize{100, 100};
+    color0_tex_desc.usage = static_cast<uint64_t>(TextureUsage::kRenderTarget);
+
+    auto color0_msaa_tex = allocator.CreateTexture(color0_tex_desc);
+
+    // Color attachment.
+
+    ColorAttachment color0;
+    color0.load_action = LoadAction::kDontCare;
+    color0.store_action = StoreAction::kStoreAndMultisampleResolve;
+    color0.texture = color0_msaa_tex;
+    color0.resolve_texture = color0_msaa_tex;
+
+    render_target.SetColorAttachment(color0, 0u);
+    render_target.SetStencilAttachment(std::nullopt);
+  }
+
+  auto entity_pass_target = EntityPassTarget(render_target, false, true);
+
+  auto color0 = entity_pass_target.GetRenderTarget()
+                    .GetColorAttachments()
+                    .find(0u)
+                    ->second;
+  auto msaa_tex = color0.texture;
+  auto resolve_tex = color0.resolve_texture;
+
+  ASSERT_EQ(msaa_tex, resolve_tex);
+
+  entity_pass_target.Flip(
+      *content_context->GetContext()->GetResourceAllocator());
+
+  color0 = entity_pass_target.GetRenderTarget()
+               .GetColorAttachments()
+               .find(0u)
+               ->second;
+
+  ASSERT_NE(msaa_tex, color0.texture);
+  ASSERT_NE(resolve_tex, color0.resolve_texture);
+  ASSERT_EQ(color0.texture, color0.resolve_texture);
+}
+
+}  // namespace testing
+}  // namespace impeller