Add //impeller/typographer. (flutter#36)

Renders shaped text frames. Has the ability to plug into to different text
shapers and render glyphs using different techniques.

For now, the Aiks layer expects a prepared glyph atlas. But this will be changed
so that render pass will be responsible for preparing these and setting these on
the content renderer after pass consolidation.

Author: chinmaygarde

impeller/BUILD.gn

@@ -21,6 +21,7 @@ group("impeller") {
     "geometry",
     "image",
     "renderer",
+    "typographer",
   ]
 
   if (is_host) {
@@ -43,5 +44,6 @@ executable("impeller_unittests") {
     "image:image_unittests",
     "playground",
     "renderer:renderer_unittests",
+    "typographer:typographer_unittests",
   ]
 }

impeller/aiks/aiks_unittests.cc

@@ -8,6 +8,9 @@
 #include "impeller/aiks/image.h"
 #include "impeller/geometry/geometry_unittests.h"
 #include "impeller/geometry/path_builder.h"
+#include "impeller/typographer/backends/skia/text_frame_skia.h"
+#include "impeller/typographer/backends/skia/text_render_context_skia.h"
+#include "third_party/skia/include/core/SkData.h"
 
 namespace impeller {
 namespace testing {
@@ -283,5 +286,114 @@ TEST_F(AiksTest, CanRenderDifferencePaths) {
   ASSERT_TRUE(OpenPlaygroundHere(canvas.EndRecordingAsPicture()));
 }
 
+static sk_sp<SkData> OpenFixtureAsSkData(const char* fixture_name) {
+  auto mapping = flutter::testing::OpenFixtureAsMapping(fixture_name);
+  if (!mapping) {
+    return nullptr;
+  }
+  return SkData::MakeWithProc(
+      mapping->GetMapping(), mapping->GetSize(),
+      [](const void* ptr, void* context) {
+        delete reinterpret_cast<fml::Mapping*>(context);
+      },
+      mapping.release());
+}
+
+TEST_F(AiksTest, CanRenderTextFrame) {
+  Canvas canvas;
+
+  Scalar baseline = 200.0;
+  Point text_position = {100, baseline};
+
+  // Draw the baseline.
+  canvas.DrawRect({50, baseline, 900, 10},
+                  Paint{.color = Color::Aqua().WithAlpha(0.25)});
+
+  // Mark the point at which the text is drawn.
+  canvas.DrawCircle(text_position, 5.0,
+                    Paint{.color = Color::Red().WithAlpha(0.25)});
+
+  // Construct the text blob.
+  auto mapping = OpenFixtureAsSkData("Roboto-Regular.ttf");
+  ASSERT_TRUE(mapping);
+  SkFont sk_font(SkTypeface::MakeFromData(mapping), 50.0);
+  auto blob = SkTextBlob::MakeFromString(
+      "the quick brown fox jumped over the lazy dog!.?", sk_font);
+  ASSERT_TRUE(blob);
+
+  // Create the Impeller text frame and draw it at the designated baseline.
+  auto frame = TextFrameFromTextBlob(blob);
+  TextRenderContextSkia text_context(GetContext());
+  ASSERT_TRUE(text_context.IsValid());
+  auto atlas = text_context.CreateGlyphAtlas(frame);
+  ASSERT_NE(atlas, nullptr);
+  canvas.DrawTextFrame(std::move(frame), std::move(atlas), text_position);
+  ASSERT_TRUE(OpenPlaygroundHere(canvas.EndRecordingAsPicture()));
+}
+
+TEST_F(AiksTest, CanRenderItalicizedText) {
+  Canvas canvas;
+
+  Scalar baseline = 200.0;
+  Point text_position = {100, baseline};
+
+  // Draw the baseline.
+  canvas.DrawRect({50, baseline, 900, 10},
+                  Paint{.color = Color::Aqua().WithAlpha(0.25)});
+
+  // Mark the point at which the text is drawn.
+  canvas.DrawCircle(text_position, 5.0,
+                    Paint{.color = Color::Red().WithAlpha(0.25)});
+
+  // Construct the text blob.
+  auto mapping = OpenFixtureAsSkData("HomemadeApple.ttf");
+  ASSERT_TRUE(mapping);
+  SkFont sk_font(SkTypeface::MakeFromData(mapping), 50.0);
+  auto blob = SkTextBlob::MakeFromString(
+      "the quick brown fox jumped over the lazy dog!.?", sk_font);
+  ASSERT_TRUE(blob);
+
+  // Create the Impeller text frame and draw it at the designated baseline.
+  auto frame = TextFrameFromTextBlob(blob);
+  TextRenderContextSkia text_context(GetContext());
+  ASSERT_TRUE(text_context.IsValid());
+  auto atlas = text_context.CreateGlyphAtlas(frame);
+  ASSERT_NE(atlas, nullptr);
+  canvas.DrawTextFrame(std::move(frame), std::move(atlas), text_position);
+  ASSERT_TRUE(OpenPlaygroundHere(canvas.EndRecordingAsPicture()));
+}
+
+TEST_F(AiksTest, CanRenderEmojiTextFrame) {
+  Canvas canvas;
+
+  Scalar baseline = 200.0;
+  Point text_position = {100, baseline};
+
+  // Draw the baseline.
+  canvas.DrawRect({50, baseline, 900, 10},
+                  Paint{.color = Color::Aqua().WithAlpha(0.25)});
+
+  // Mark the point at which the text is drawn.
+  canvas.DrawCircle(text_position, 5.0,
+                    Paint{.color = Color::Red().WithAlpha(0.25)});
+
+  // Construct the text blob.
+  auto mapping = OpenFixtureAsSkData("NotoColorEmoji.ttf");
+  ASSERT_TRUE(mapping);
+  SkFont sk_font(SkTypeface::MakeFromData(mapping), 50.0);
+  auto blob = SkTextBlob::MakeFromString(
+      "😀 😃 😄 😁 😆 😅 😂 🤣 🥲 ☺️ 😊", sk_font);
+  ASSERT_TRUE(blob);
+
+  // Create the Impeller text frame and draw it at the designated baseline.
+  auto frame = TextFrameFromTextBlob(blob);
+  TextRenderContextSkia text_context(GetContext());
+  ASSERT_TRUE(text_context.IsValid());
+  auto atlas = text_context.CreateGlyphAtlas(frame);
+  ASSERT_NE(atlas, nullptr);
+  canvas.DrawTextFrame(std::move(frame), std::move(atlas), text_position);
+  ASSERT_TRUE(OpenPlaygroundHere(canvas.EndRecordingAsPicture()));
+}
+
 }  // namespace testing
 }  // namespace impeller

impeller/aiks/canvas.cc

@@ -252,4 +252,25 @@ void Canvas::Save(bool create_subpass) {
   xformation_stack_.emplace_back(std::move(entry));
 }
 
+void Canvas::DrawTextFrame(TextFrame text_frame,
+                           std::shared_ptr<GlyphAtlas> atlas,
+                           Point position) {
+  if (!atlas || !atlas->IsValid()) {
+    return;
+  }
+
+  auto text_contents = std::make_shared<TextContents>();
+  text_contents->SetTextFrame(std::move(text_frame));
+  text_contents->SetGlyphAtlas(std::move(atlas));
+
+  Entity entity;
+  entity.SetTransformation(GetCurrentTransformation() *
+                           Matrix::MakeTranslation(position));
+  entity.SetPath({});
+  entity.SetStencilDepth(GetStencilDepth());
+  entity.SetContents(std::move(text_contents));
+
+  GetCurrentPass().AddEntity(std::move(entity));
+}
+
 }  // namespace impeller

impeller/aiks/canvas.h

@@ -18,6 +18,7 @@
 #include "impeller/geometry/path.h"
 #include "impeller/geometry/point.h"
 #include "impeller/geometry/vector.h"
+#include "impeller/typographer/text_frame.h"
 
 namespace impeller {
 
@@ -74,6 +75,10 @@ class Canvas {
 
   void DrawPicture(Picture picture);
 
+  void DrawTextFrame(TextFrame text_frame,
+                     std::shared_ptr<GlyphAtlas> atlas,
+                     Point position);
+
   Picture EndRecordingAsPicture();
 
  private:

impeller/aiks/paint.cc

@@ -7,6 +7,10 @@
 namespace impeller {
 
 std::shared_ptr<Contents> Paint::CreateContentsForEntity() const {
+  if (contents) {
+    return contents;
+  }
+
   switch (style) {
     case Style::kFill: {
       auto solid_color = std::make_shared<SolidColorContents>();

impeller/aiks/paint.h

@@ -21,6 +21,7 @@ struct Paint {
   Color color = Color::Black();
   Scalar stroke_width = 0.0;
   Style style = Style::kFill;
+  std::shared_ptr<Contents> contents;
 
   std::shared_ptr<Contents> CreateContentsForEntity() const;
 };

impeller/base/BUILD.gn

@@ -8,6 +8,7 @@ impeller_component("base") {
   sources = [
     "allocation.cc",
     "allocation.h",
+    "backend_cast.h",
     "base.h",
     "config.h",
     "promise.cc",

impeller/base/allocation.cc

@@ -38,7 +38,7 @@ bool Allocation::Truncate(size_t length, bool npot) {
   return true;
 }
 
-static uint32_t NextPowerOfTwoSize(uint32_t x) {
+uint32_t Allocation::NextPowerOfTwoSize(uint32_t x) {
   if (x == 0) {
     return 1;
   }

impeller/base/allocation.h

@@ -25,6 +25,8 @@ class Allocation {
 
   [[nodiscard]] bool Truncate(size_t length, bool npot = true);
 
+  static uint32_t NextPowerOfTwoSize(uint32_t x);
+
  private:
   uint8_t* buffer_ = nullptr;
   size_t length_ = 0;