[Impeller] cache for text shadows. (#166228)

Fixes flutter/flutter#164303
Fixes flutter/flutter#165116

When rendering a text shadow, cache the resulting snapshot for at least
one frame. Only attempts to content-aware hash for single glyphs
(Icons). in other cases the exact layout may be different enough that
its not worth trying to cache.

Author: Jonah Williams

engine/src/flutter/ci/licenses_golden/licenses_flutter

@@ -51252,6 +51252,8 @@ ORIGIN: ../../../flutter/impeller/entity/contents/sweep_gradient_contents.cc + .
 ORIGIN: ../../../flutter/impeller/entity/contents/sweep_gradient_contents.h + ../../../flutter/LICENSE
 ORIGIN: ../../../flutter/impeller/entity/contents/text_contents.cc + ../../../flutter/LICENSE
 ORIGIN: ../../../flutter/impeller/entity/contents/text_contents.h + ../../../flutter/LICENSE
+ORIGIN: ../../../flutter/impeller/entity/contents/text_shadow_cache.cc + ../../../flutter/LICENSE
+ORIGIN: ../../../flutter/impeller/entity/contents/text_shadow_cache.h + ../../../flutter/LICENSE
 ORIGIN: ../../../flutter/impeller/entity/contents/texture_contents.cc + ../../../flutter/LICENSE
 ORIGIN: ../../../flutter/impeller/entity/contents/texture_contents.h + ../../../flutter/LICENSE
 ORIGIN: ../../../flutter/impeller/entity/contents/tiled_texture_contents.cc + ../../../flutter/LICENSE
@@ -54240,6 +54242,8 @@ FILE: ../../../flutter/impeller/entity/contents/sweep_gradient_contents.cc
 FILE: ../../../flutter/impeller/entity/contents/sweep_gradient_contents.h
 FILE: ../../../flutter/impeller/entity/contents/text_contents.cc
 FILE: ../../../flutter/impeller/entity/contents/text_contents.h
+FILE: ../../../flutter/impeller/entity/contents/text_shadow_cache.cc
+FILE: ../../../flutter/impeller/entity/contents/text_shadow_cache.h
 FILE: ../../../flutter/impeller/entity/contents/texture_contents.cc
 FILE: ../../../flutter/impeller/entity/contents/texture_contents.h
 FILE: ../../../flutter/impeller/entity/contents/tiled_texture_contents.cc

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

@@ -13,6 +13,9 @@
 #include "flutter/fml/build_config.h"
 #include "flutter/impeller/display_list/aiks_unittests.h"
 #include "flutter/testing/testing.h"
+#include "impeller/display_list/aiks_context.h"
+#include "impeller/display_list/dl_dispatcher.h"
+#include "impeller/entity/contents/content_context.h"
 #include "impeller/entity/contents/text_contents.h"
 #include "impeller/entity/entity.h"
 #include "impeller/geometry/matrix.h"
@@ -41,7 +44,8 @@ bool RenderTextInCanvasSkia(const std::shared_ptr<Context>& context,
                             DisplayListBuilder& canvas,
                             const std::string& text,
                             const std::string_view& font_fixture,
-                            const TextRenderOptions& options = {}) {
+                            const TextRenderOptions& options = {},
+                            const std::optional<SkFont>& font = std::nullopt) {
   // Draw the baseline.
   DlPaint paint;
   paint.setColor(DlColor::kAqua().withAlpha(255 * 0.25));
@@ -54,17 +58,23 @@ bool RenderTextInCanvasSkia(const std::shared_ptr<Context>& context,
   canvas.DrawCircle(options.position, 5.0, paint);
 
   // Construct the text blob.
-  auto c_font_fixture = std::string(font_fixture);
-  auto mapping = flutter::testing::OpenFixtureAsSkData(c_font_fixture.c_str());
-  if (!mapping) {
-    return false;
-  }
-  sk_sp<SkFontMgr> font_mgr = txt::GetDefaultFontManager();
-  SkFont sk_font(font_mgr->makeFromData(mapping), options.font_size);
-  if (options.is_subpixel) {
-    sk_font.setSubpixel(true);
+  SkFont selected_font;
+  if (!font.has_value()) {
+    auto c_font_fixture = std::string(font_fixture);
+    auto mapping =
+        flutter::testing::OpenFixtureAsSkData(c_font_fixture.c_str());
+    if (!mapping) {
+      return false;
+    }
+    sk_sp<SkFontMgr> font_mgr = txt::GetDefaultFontManager();
+    selected_font = SkFont(font_mgr->makeFromData(mapping), options.font_size);
+    if (options.is_subpixel) {
+      selected_font.setSubpixel(true);
+    }
+  } else {
+    selected_font = font.value();
   }
-  auto blob = SkTextBlob::MakeFromString(text.c_str(), sk_font);
+  auto blob = SkTextBlob::MakeFromString(text.c_str(), selected_font);
   if (!blob) {
     return false;
   }
@@ -731,5 +741,108 @@ TEST_P(AiksTest, TextContentsMismatchedTransformTest) {
                                    *render_pass));
 }
 
+TEST_P(AiksTest, TextWithShadowCache) {
+  DisplayListBuilder builder;
+  builder.Scale(GetContentScale().x, GetContentScale().y);
+  DlPaint paint;
+  paint.setColor(DlColor::ARGB(1, 0.1, 0.1, 0.1));
+  builder.DrawPaint(paint);
+
+  AiksContext aiks_context(GetContext(),
+                           std::make_shared<TypographerContextSkia>());
+  // Cache empty
+  EXPECT_EQ(aiks_context.GetContentContext()
+                .GetTextShadowCache()
+                .GetCacheSizeForTesting(),
+            0u);
+
+  ASSERT_TRUE(RenderTextInCanvasSkia(
+      GetContext(), builder, "Hello World", kFontFixture,
+      TextRenderOptions{
+          .color = DlColor::kBlue(),
+          .filter = DlBlurMaskFilter::Make(DlBlurStyle::kNormal, 4)}));
+
+  DisplayListToTexture(builder.Build(), {400, 400}, aiks_context);
+
+  // Text should be cached.
+  EXPECT_EQ(aiks_context.GetContentContext()
+                .GetTextShadowCache()
+                .GetCacheSizeForTesting(),
+            1u);
+}
+
+TEST_P(AiksTest, MultipleTextWithShadowCache) {
+  DisplayListBuilder builder;
+  builder.Scale(GetContentScale().x, GetContentScale().y);
+  DlPaint paint;
+  paint.setColor(DlColor::ARGB(1, 0.1, 0.1, 0.1));
+  builder.DrawPaint(paint);
+
+  AiksContext aiks_context(GetContext(),
+                           std::make_shared<TypographerContextSkia>());
+  // Cache empty
+  EXPECT_EQ(aiks_context.GetContentContext()
+                .GetTextShadowCache()
+                .GetCacheSizeForTesting(),
+            0u);
+
+  for (auto i = 0; i < 5; i++) {
+    ASSERT_TRUE(RenderTextInCanvasSkia(
+        GetContext(), builder, "Hello World", kFontFixture,
+        TextRenderOptions{
+            .color = DlColor::kBlue(),
+            .filter = DlBlurMaskFilter::Make(DlBlurStyle::kNormal, 4)}));
+  }
+
+  DisplayListToTexture(builder.Build(), {400, 400}, aiks_context);
+
+  // Text should be cached. Each text gets its own entry as we don't analyze the
+  // strings.
+  EXPECT_EQ(aiks_context.GetContentContext()
+                .GetTextShadowCache()
+                .GetCacheSizeForTesting(),
+            5u);
+}
+
+TEST_P(AiksTest, SingleIconShadowTest) {
+  DisplayListBuilder builder;
+  builder.Scale(GetContentScale().x, GetContentScale().y);
+  DlPaint paint;
+  paint.setColor(DlColor::ARGB(1, 0.1, 0.1, 0.1));
+  builder.DrawPaint(paint);
+
+  AiksContext aiks_context(GetContext(),
+                           std::make_shared<TypographerContextSkia>());
+  // Cache empty
+  EXPECT_EQ(aiks_context.GetContentContext()
+                .GetTextShadowCache()
+                .GetCacheSizeForTesting(),
+            0u);
+
+  // Create font instance outside loop so all draws use identical font instance.
+  auto c_font_fixture = std::string(kFontFixture);
+  auto mapping = flutter::testing::OpenFixtureAsSkData(c_font_fixture.c_str());
+  ASSERT_TRUE(mapping);
+  sk_sp<SkFontMgr> font_mgr = txt::GetDefaultFontManager();
+  SkFont sk_font(font_mgr->makeFromData(mapping), 50);
+
+  for (auto i = 0; i < 10; i++) {
+    ASSERT_TRUE(RenderTextInCanvasSkia(
+        GetContext(), builder, "A", kFontFixture,
+        TextRenderOptions{
+            .color = DlColor::kBlue(),
+            .filter = DlBlurMaskFilter::Make(DlBlurStyle::kNormal, 4)},
+        sk_font));
+  }
+
+  DisplayListToTexture(builder.Build(), {400, 400}, aiks_context);
+
+  // Text should be cached. All 10 glyphs use the same cache entry.
+  EXPECT_EQ(aiks_context.GetContentContext()
+                .GetTextShadowCache()
+                .GetCacheSizeForTesting(),
+            1u);
+}
+
 }  // namespace testing
 }  // namespace impeller

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

@@ -78,6 +78,7 @@ TEST_P(AiksTest, CollapsedDrawPaintInSubpassBackdropFilter) {
 
 TEST_P(AiksTest, ColorMatrixFilterSubpassCollapseOptimization) {
   DisplayListBuilder builder(DlRect::MakeSize(GetWindowSize()));
+  builder.DrawPaint(DlPaint().setColor(DlColor::kWhite()));
 
   const float matrix[20] = {
       -1.0, 0,    0,    1.0, 0,  //

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

@@ -20,7 +20,6 @@
 #include "impeller/base/validation.h"
 #include "impeller/core/formats.h"
 #include "impeller/display_list/color_filter.h"
-#include "impeller/display_list/dl_atlas_geometry.h"
 #include "impeller/display_list/image_filter.h"
 #include "impeller/display_list/skia_conversions.h"
 #include "impeller/entity/contents/atlas_contents.h"
@@ -32,6 +31,7 @@
 #include "impeller/entity/contents/line_contents.h"
 #include "impeller/entity/contents/solid_rrect_blur_contents.h"
 #include "impeller/entity/contents/text_contents.h"
+#include "impeller/entity/contents/text_shadow_cache.h"
 #include "impeller/entity/contents/texture_contents.h"
 #include "impeller/entity/contents/vertices_contents.h"
 #include "impeller/entity/geometry/circle_geometry.h"
@@ -1467,6 +1467,50 @@ bool Canvas::Restore() {
   return true;
 }
 
+bool Canvas::AttemptBlurredTextOptimization(
+    const std::shared_ptr<TextFrame>& text_frame,
+    const std::shared_ptr<TextContents>& text_contents,
+    Entity& entity,
+    const Paint& paint) {
+  if (!paint.mask_blur_descriptor.has_value() ||  //
+      paint.image_filter != nullptr ||            //
+      paint.color_filter != nullptr ||            //
+      paint.invert_colors) {
+    return false;
+  }
+
+  // TODO(bdero): This mask blur application is a hack. It will always wind up
+  //              doing a gaussian blur that affects the color source itself
+  //              instead of just the mask. The color filter text support
+  //              needs to be reworked in order to interact correctly with
+  //              mask filters.
+  //              https://github.com/flutter/flutter/issues/133297
+  std::shared_ptr<FilterContents> filter =
+      paint.mask_blur_descriptor->CreateMaskBlur(
+          FilterInput::Make(text_contents),
+          /*is_solid_color=*/true, GetCurrentTransform());
+
+  std::optional<Glyph> maybe_glyph = text_frame->AsSingleGlyph();
+  int64_t identifier = maybe_glyph.has_value()
+                           ? maybe_glyph.value().index
+                           : reinterpret_cast<int64_t>(text_frame.get());
+  TextShadowCache::TextShadowCacheKey cache_key(
+      /*p_max_basis=*/entity.GetTransform().GetMaxBasisLengthXY(),
+      /*p_identifier=*/identifier,
+      /*p_is_single_glyph=*/maybe_glyph.has_value(),
+      /*p_font=*/text_frame->GetFont(),
+      /*p_sigma=*/paint.mask_blur_descriptor->sigma);
+
+  std::optional<Entity> result = renderer_.GetTextShadowCache().Lookup(
+      renderer_, entity, filter, cache_key);
+  if (result.has_value()) {
+    AddRenderEntityToCurrentPass(result.value(), /*reuse_depth=*/false);
+    return true;
+  } else {
+    return false;
+  }
+}
+
 void Canvas::DrawTextFrame(const std::shared_ptr<TextFrame>& text_frame,
                            Point position,
                            const Paint& paint) {
@@ -1491,15 +1535,12 @@ void Canvas::DrawTextFrame(const std::shared_ptr<TextFrame>& text_frame,
   entity.SetTransform(GetCurrentTransform() *
                       Matrix::MakeTranslation(position));
 
-  // TODO(bdero): This mask blur application is a hack. It will always wind up
-  //              doing a gaussian blur that affects the color source itself
-  //              instead of just the mask. The color filter text support
-  //              needs to be reworked in order to interact correctly with
-  //              mask filters.
-  //              https://github.com/flutter/flutter/issues/133297
-  entity.SetContents(paint.WithFilters(paint.WithMaskBlur(
-      std::move(text_contents), true, GetCurrentTransform())));
+  if (AttemptBlurredTextOptimization(text_frame, text_contents, entity,
+                                     paint)) {
+    return;
+  }
 
+  entity.SetContents(paint.WithFilters(std::move(text_contents)));
   AddRenderEntityToCurrentPass(entity, false);
 }
 

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

@@ -17,6 +17,7 @@
 #include "impeller/display_list/paint.h"
 #include "impeller/entity/contents/atlas_contents.h"
 #include "impeller/entity/contents/clip_contents.h"
+#include "impeller/entity/contents/text_contents.h"
 #include "impeller/entity/entity.h"
 #include "impeller/entity/entity_pass_clip_stack.h"
 #include "impeller/entity/geometry/geometry.h"
@@ -368,6 +369,12 @@ class Canvas {
                                       const SamplerDescriptor& sampler,
                                       SourceRectConstraint src_rect_constraint);
 
+  bool AttemptBlurredTextOptimization(
+      const std::shared_ptr<TextFrame>& text_frame,
+      const std::shared_ptr<TextContents>& text_contents,
+      Entity& entity,
+      const Paint& paint);
+
   RenderPass& GetCurrentRenderPass() const;
 
   Canvas(const Canvas&) = delete;

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

@@ -13,6 +13,7 @@
 #include "display_list/dl_sampling_options.h"
 #include "display_list/effects/dl_image_filter.h"
 #include "flutter/fml/logging.h"
+#include "fml/closure.h"
 #include "impeller/core/formats.h"
 #include "impeller/display_list/aiks_context.h"
 #include "impeller/display_list/canvas.h"
@@ -1333,15 +1334,19 @@ std::shared_ptr<Texture> DisplayListToTexture(
   );
   const auto& [data, count] = collector.TakeBackdropData();
   impeller_dispatcher.SetBackdropData(data, count);
+  context.GetContentContext().GetTextShadowCache().MarkFrameStart();
+  fml::ScopedCleanupClosure cleanup([&] {
+    if (reset_host_buffer) {
+      context.GetContentContext().GetTransientsBuffer().Reset();
+    }
+    context.GetContentContext().GetTextShadowCache().MarkFrameEnd();
+    context.GetContentContext().GetLazyGlyphAtlas()->ResetTextFrames();
+    context.GetContext()->DisposeThreadLocalCachedResources();
+  });
+
   display_list->Dispatch(impeller_dispatcher, sk_cull_rect);
   impeller_dispatcher.FinishRecording();
 
-  if (reset_host_buffer) {
-    context.GetContentContext().GetTransientsBuffer().Reset();
-  }
-  context.GetContentContext().GetLazyGlyphAtlas()->ResetTextFrames();
-  context.GetContext()->DisposeThreadLocalCachedResources();
-
   return target.GetRenderTargetTexture();
 }
 
@@ -1366,11 +1371,16 @@ bool RenderToTarget(ContentContext& context,
   );
   const auto& [data, count] = collector.TakeBackdropData();
   impeller_dispatcher.SetBackdropData(data, count);
+  context.GetTextShadowCache().MarkFrameStart();
+  fml::ScopedCleanupClosure cleanup([&] {
+    if (reset_host_buffer) {
+      context.GetTransientsBuffer().Reset();
+    }
+    context.GetTextShadowCache().MarkFrameEnd();
+  });
+
   display_list->Dispatch(impeller_dispatcher, cull_rect);
   impeller_dispatcher.FinishRecording();
-  if (reset_host_buffer) {
-    context.GetTransientsBuffer().Reset();
-  }
   context.GetLazyGlyphAtlas()->ResetTextFrames();
 
   return true;

engine/src/flutter/impeller/entity/BUILD.gn

@@ -179,6 +179,8 @@ impeller_component("entity") {
     "contents/sweep_gradient_contents.h",
     "contents/text_contents.cc",
     "contents/text_contents.h",
+    "contents/text_shadow_cache.cc",
+    "contents/text_shadow_cache.h",
     "contents/texture_contents.cc",
     "contents/texture_contents.h",
     "contents/tiled_texture_contents.cc",

engine/src/flutter/impeller/entity/contents/content_context.cc

@@ -13,6 +13,7 @@
 #include "impeller/core/texture_descriptor.h"
 #include "impeller/entity/contents/framebuffer_blend_contents.h"
 #include "impeller/entity/contents/pipelines.h"
+#include "impeller/entity/contents/text_shadow_cache.h"
 #include "impeller/entity/entity.h"
 #include "impeller/entity/render_target_cache.h"
 #include "impeller/renderer/command_buffer.h"
@@ -532,7 +533,8 @@ ContentContext::ContentContext(
                                      context_->GetResourceAllocator())
                                : std::move(render_target_allocator)),
       host_buffer_(HostBuffer::Create(context_->GetResourceAllocator(),
-                                      context_->GetIdleWaiter())) {
+                                      context_->GetIdleWaiter())),
+      text_shadow_cache_(std::make_unique<TextShadowCache>()) {
   if (!context_ || !context_->IsValid()) {
     return;
   }