[Impeller] if drawTextFrame scale is massive, convert to Path. (#166234)

Fixes https://github.com/flutter/flutter/issues/165583
Fixes https://github.com/flutter/flutter/issues/136112

If the text scale gets too big, its faster (and higher res) to switch to
path rendering than to keep using the glyph atlas cache.

engine/src/flutter/display_list/testing/dl_rendering_unittests.cc

@@ -3900,7 +3900,6 @@ TEST_F(DisplayListRendering, DrawTextBlob) {
       // ~12 on top and ~8 on the bottom, so we add 33h & 13v allowed
       // padding to the tolerance
       CanvasCompareTester::DefaultTolerance.addBoundsPadding(33, 13));
-  EXPECT_TRUE(blob->unique());
 #endif  // OS_FUCHSIA
 }
 

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

@@ -190,6 +190,34 @@ TEST_P(AiksTest, ScaledK) {
   ASSERT_TRUE(OpenPlaygroundHere(builder.Build()));
 }
 
+// This is a test that looks for glyph artifacts we've see.
+TEST_P(AiksTest, MassiveScaleConvertToPath) {
+  Scalar scale = 16.0;
+  auto callback = [&]() -> sk_sp<DisplayList> {
+    if (AiksTest::ImGuiBegin("Controls", nullptr,
+                             ImGuiWindowFlags_AlwaysAutoResize)) {
+      ImGui::SliderFloat("Scale", &scale, 4, 20);
+      ImGui::End();
+    }
+
+    DisplayListBuilder builder;
+    DlPaint paint;
+    paint.setColor(DlColor::ARGB(1, 0.1, 0.1, 0.1));
+    builder.DrawPaint(paint);
+
+    builder.Scale(scale, scale);
+    RenderTextInCanvasSkia(
+        GetContext(), builder, "HELLO", "Roboto-Regular.ttf",
+        TextRenderOptions{.font_size = 16,
+                          .color = (16 * scale >= 250) ? DlColor::kYellow()
+                                                       : DlColor::kOrange(),
+                          .position = DlPoint(0, 20)});
+    return builder.Build();
+  };
+
+  ASSERT_TRUE(OpenPlaygroundHere(callback));
+}
+
 TEST_P(AiksTest, CanRenderTextFrameWithScalingOverflow) {
   Scalar scale = 60.0;
   Scalar offsetx = -500.0;
@@ -844,5 +872,32 @@ TEST_P(AiksTest, SingleIconShadowTest) {
             1u);
 }
 
+TEST_P(AiksTest, VarietyOfTextScalesShowingRasterAndPath) {
+  DisplayListBuilder builder;
+  DlPaint paint;
+  paint.setColor(DlColor::ARGB(1, 0.1, 0.1, 0.1));
+  builder.DrawPaint(paint);
+  builder.Scale(GetContentScale().x, GetContentScale().y);
+
+  std::vector<Scalar> scales = {4, 8, 16, 24, 32};
+  std::vector<Scalar> spacing = {8, 8, 8, 8, 8};
+  Scalar space = 16;
+  Scalar x = 0;
+  for (auto i = 0u; i < scales.size(); i++) {
+    builder.Save();
+    builder.Scale(scales[i], scales[i]);
+    RenderTextInCanvasSkia(
+        GetContext(), builder, "lo", "Roboto-Regular.ttf",
+        TextRenderOptions{.font_size = 16, .position = DlPoint(x, space)});
+    space += spacing[i];
+    if (i == 3) {
+      x = 10;
+      space = 16;
+    }
+    builder.Restore();
+  }
+  ASSERT_TRUE(OpenPlaygroundHere(builder.Build()));
+}
+
 }  // namespace testing
 }  // namespace impeller

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

@@ -14,6 +14,7 @@
 #include "display_list/effects/dl_color_filter.h"
 #include "display_list/effects/dl_color_source.h"
 #include "display_list/effects/dl_image_filter.h"
+#include "display_list/geometry/dl_path.h"
 #include "display_list/image/dl_image.h"
 #include "flutter/fml/logging.h"
 #include "flutter/fml/trace_event.h"
@@ -1511,9 +1512,27 @@ bool Canvas::AttemptBlurredTextOptimization(
   }
 }
 
+// If the text point size * max basis XY is larger than this value,
+// render the text as paths (if available) for faster and higher
+// fidelity rendering. This is a somewhat arbitrary cutoff
+static constexpr Scalar kMaxTextScale = 250;
+
 void Canvas::DrawTextFrame(const std::shared_ptr<TextFrame>& text_frame,
                            Point position,
                            const Paint& paint) {
+  Scalar max_scale = GetCurrentTransform().GetMaxBasisLengthXY();
+  if (max_scale * text_frame->GetFont().GetMetrics().point_size >
+      kMaxTextScale) {
+    fml::StatusOr<flutter::DlPath> path = text_frame->GetPath();
+    if (path.ok()) {
+      Save(1);
+      Concat(Matrix::MakeTranslation(position));
+      DrawPath(path.value().GetPath(), paint);
+      Restore();
+      return;
+    }
+  }
+
   Entity entity;
   entity.SetClipDepth(GetClipHeight());
   entity.SetBlendMode(paint.blend_mode);
@@ -1521,7 +1540,7 @@ void Canvas::DrawTextFrame(const std::shared_ptr<TextFrame>& text_frame,
   auto text_contents = std::make_shared<TextContents>();
   text_contents->SetTextFrame(text_frame);
   text_contents->SetForceTextColor(paint.mask_blur_descriptor.has_value());
-  text_contents->SetScale(GetCurrentTransform().GetMaxBasisLengthXY());
+  text_contents->SetScale(max_scale);
   text_contents->SetColor(paint.color);
   text_contents->SetOffset(position);
   text_contents->SetTextProperties(paint.color,                           //

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

@@ -39,7 +39,10 @@ impeller_component("typographer") {
         [ "//flutter/third_party/abseil-cpp/absl/container:flat_hash_map" ]
   }
 
-  deps = [ "//flutter/fml" ]
+  deps = [
+    "//flutter/fml",
+    "//flutter/skia",
+  ]
 }
 
 impeller_component("typographer_unittests") {

engine/src/flutter/impeller/typographer/backends/skia/text_frame_skia.cc

@@ -6,7 +6,9 @@
 
 #include <vector>
 
+#include "flutter/display_list/geometry/dl_path.h"
 #include "flutter/fml/logging.h"
+#include "fml/status.h"
 #include "impeller/typographer/backends/skia/typeface_skia.h"
 #include "impeller/typographer/font.h"
 #include "impeller/typographer/glyph.h"
@@ -14,6 +16,7 @@
 #include "third_party/skia/include/core/SkFontMetrics.h"
 #include "third_party/skia/include/core/SkPaint.h"
 #include "third_party/skia/include/core/SkRect.h"
+#include "third_party/skia/modules/skparagraph/include/Paragraph.h"  // nogncheck
 #include "third_party/skia/src/core/SkStrikeSpec.h"    // nogncheck
 #include "third_party/skia/src/core/SkTextBlobPriv.h"  // nogncheck
 
@@ -83,7 +86,17 @@ std::shared_ptr<TextFrame> MakeTextFrameFromTextBlobSkia(
         continue;
     }
   }
-  return std::make_shared<TextFrame>(runs, ToRect(blob->bounds()), has_color);
+  return std::make_shared<TextFrame>(
+      runs, ToRect(blob->bounds()), has_color,
+      [blob]() -> fml::StatusOr<flutter::DlPath> {
+        SkPath path = skia::textlayout::Paragraph::GetPath(blob.get());
+        if (path.isEmpty()) {
+          return fml::Status(fml::StatusCode::kCancelled, "No path available");
+        }
+        SkPath transformed = path.makeTransform(
+            SkMatrix::Translate(blob->bounds().left(), blob->bounds().top()));
+        return flutter::DlPath(transformed);
+      });
 }
 
 }  // namespace impeller

engine/src/flutter/impeller/typographer/text_frame.cc

@@ -3,6 +3,8 @@
 // found in the LICENSE file.
 
 #include "impeller/typographer/text_frame.h"
+#include "flutter/display_list/geometry/dl_path.h"  // nogncheck
+#include "fml/status.h"
 #include "impeller/geometry/scalar.h"
 #include "impeller/typographer/font.h"
 #include "impeller/typographer/font_glyph_pair.h"
@@ -11,8 +13,14 @@ namespace impeller {
 
 TextFrame::TextFrame() = default;
 
-TextFrame::TextFrame(std::vector<TextRun>& runs, Rect bounds, bool has_color)
-    : runs_(std::move(runs)), bounds_(bounds), has_color_(has_color) {}
+TextFrame::TextFrame(std::vector<TextRun>& runs,
+                     Rect bounds,
+                     bool has_color,
+                     const PathCreator& path_creator)
+    : runs_(std::move(runs)),
+      bounds_(bounds),
+      has_color_(has_color),
+      path_creator_(path_creator) {}
 
 TextFrame::~TextFrame() = default;
 
@@ -138,6 +146,13 @@ void TextFrame::ClearFrameBounds() {
   bound_values_.clear();
 }
 
+fml::StatusOr<flutter::DlPath> TextFrame::GetPath() const {
+  if (path_creator_) {
+    return path_creator_();
+  }
+  return fml::Status(fml::StatusCode::kCancelled, "no path creator specified.");
+}
+
 bool TextFrame::IsFrameComplete() const {
   size_t run_size = 0;
   for (const auto& x : runs_) {

engine/src/flutter/impeller/typographer/text_frame.h

@@ -6,13 +6,23 @@
 #define FLUTTER_IMPELLER_TYPOGRAPHER_TEXT_FRAME_H_
 
 #include <cstdint>
+
+#include "fml/status_or.h"
 #include "impeller/geometry/rational.h"
 #include "impeller/typographer/glyph.h"
 #include "impeller/typographer/glyph_atlas.h"
 #include "impeller/typographer/text_run.h"
 
+// TODO(https://github.com/flutter/flutter/issues/166593): This is required to
+// break a cyclical dependency between display list, impeller, and typographer.
+namespace flutter {
+class DlPath;
+}
+
 namespace impeller {
 
+using PathCreator = std::function<fml::StatusOr<flutter::DlPath>()>;
+
 //------------------------------------------------------------------------------
 /// @brief      Represents a collection of shaped text runs.
 ///
@@ -25,7 +35,10 @@ class TextFrame {
  public:
   TextFrame();
 
-  TextFrame(std::vector<TextRun>& runs, Rect bounds, bool has_color);
+  TextFrame(std::vector<TextRun>& runs,
+            Rect bounds,
+            bool has_color,
+            const PathCreator& path_creator = {});
 
   ~TextFrame();
 
@@ -103,12 +116,10 @@ class TextFrame {
 
   Rational GetScale() const;
 
-  TextFrame& operator=(TextFrame&& other) = default;
-
-  TextFrame(const TextFrame& other) = default;
-
   const Matrix& GetTransform() const { return transform_; }
 
+  fml::StatusOr<flutter::DlPath> GetPath() const;
+
   Point GetOffset() const;
 
   Matrix GetOffsetTransform() const;
@@ -128,6 +139,7 @@ class TextFrame {
   std::vector<TextRun> runs_;
   Rect bounds_;
   bool has_color_;
+  const PathCreator path_creator_;
 
   // Data that is cached when rendering the text frame and is only
   // valid for the current atlas generation.

engine/src/flutter/txt/src/skia/paragraph_skia.cc

@@ -76,7 +76,7 @@ class DisplayListParagraphPainter : public skt::ParagraphPainter {
     if (impeller_enabled_) {
       SkTextBlobRunIterator run(blob.get());
       if (ShouldRenderAsPath(dl_paints_[paint_id])) {
-        auto path = skia::textlayout::Paragraph::GetPath(blob.get());
+        SkPath path = skia::textlayout::Paragraph::GetPath(blob.get());
         // If there is no path, this is an emoji and should be drawn as is,
         // ignoring the color source.
         if (path.isEmpty()) {