[Impeller] Conditionally use A8 or R8 format glyph atlas based on capabilities.

impeller/aiks/aiks_blur_unittests.cc

@@ -354,6 +354,7 @@ TEST_P(AiksTest, GaussianBlurWithoutDecalSupport) {
   FLT_FORWARD(mock_capabilities, old_capabilities, SupportsCompute);
   FLT_FORWARD(mock_capabilities, old_capabilities,
               SupportsTextureToTextureBlits);
+  FLT_FORWARD(mock_capabilities, old_capabilities, GetDefaultGlyphAtlasFormat);
   ASSERT_TRUE(SetCapabilities(mock_capabilities).ok());
 
   auto texture = std::make_shared<Image>(CreateTextureForFixture("boston.jpg"));

impeller/entity/contents/content_context.cc

@@ -404,7 +404,11 @@ ContentContext::ContentContext(
                                                  options_trianglestrip);
   srgb_to_linear_filter_pipelines_.CreateDefault(*context_,
                                                  options_trianglestrip);
-  glyph_atlas_pipelines_.CreateDefault(*context_, options);
+  glyph_atlas_pipelines_.CreateDefault(
+      *context_, options,
+      {static_cast<Scalar>(
+          GetContext()->GetCapabilities()->GetDefaultGlyphAtlasFormat() ==
+          PixelFormat::kA8UNormInt)});
   glyph_atlas_color_pipelines_.CreateDefault(*context_, options);
   geometry_color_pipelines_.CreateDefault(*context_, options);
   yuv_to_rgb_filter_pipelines_.CreateDefault(*context_, options_trianglestrip);

impeller/entity/shaders/glyph_atlas.frag

@@ -8,6 +8,8 @@ precision mediump float;
 
 uniform f16sampler2D glyph_atlas_sampler;
 
+layout(constant_id = 0) const float use_alpha_color_channel = 1.0;
+
 in highp vec2 v_uv;
 
 IMPELLER_MAYBE_FLAT in f16vec4 v_text_color;
@@ -16,5 +18,9 @@ out f16vec4 frag_color;
 
 void main() {
   f16vec4 value = texture(glyph_atlas_sampler, v_uv);
-  frag_color = value.aaaa * v_text_color;
+  if (use_alpha_color_channel == 1.0) {
+    frag_color = value.aaaa * v_text_color;
+  } else {
+    frag_color = value.rrrr * v_text_color;
+  }
 }

impeller/renderer/backend/gles/capabilities_gles.cc

@@ -4,6 +4,7 @@
 
 #include "impeller/renderer/backend/gles/capabilities_gles.h"
 
+#include "impeller/core/formats.h"
 #include "impeller/renderer/backend/gles/proc_table_gles.h"
 
 namespace impeller {
@@ -102,6 +103,12 @@ CapabilitiesGLES::CapabilitiesGLES(const ProcTableGLES& gl) {
     num_shader_binary_formats = value;
   }
 
+  if (desc->IsES()) {
+    default_glyph_atlas_format_ = PixelFormat::kA8UNormInt;
+  } else {
+    default_glyph_atlas_format_ = PixelFormat::kR8UNormInt;
+  }
+
   supports_framebuffer_fetch_ = desc->HasExtension(kFramebufferFetchExt);
 
   if (desc->HasExtension(kTextureBorderClampExt) ||
@@ -194,4 +201,8 @@ bool CapabilitiesGLES::IsANGLE() const {
   return is_angle_;
 }
 
+PixelFormat CapabilitiesGLES::GetDefaultGlyphAtlasFormat() const {
+  return default_glyph_atlas_format_;
+}
+
 }  // namespace impeller

impeller/renderer/backend/gles/capabilities_gles.h

@@ -8,6 +8,7 @@
 #include <cstddef>
 
 #include "impeller/base/backend_cast.h"
+#include "impeller/core/formats.h"
 #include "impeller/core/shader_types.h"
 #include "impeller/geometry/size.h"
 #include "impeller/renderer/capabilities.h"
@@ -118,12 +119,16 @@ class CapabilitiesGLES final
   // |Capabilities|
   PixelFormat GetDefaultDepthStencilFormat() const override;
 
+  // |Capabilities|
+  PixelFormat GetDefaultGlyphAtlasFormat() const override;
+
  private:
   bool supports_framebuffer_fetch_ = false;
   bool supports_decal_sampler_address_mode_ = false;
   bool supports_offscreen_msaa_ = false;
   bool supports_implicit_msaa_ = false;
   bool is_angle_ = false;
+  PixelFormat default_glyph_atlas_format_ = PixelFormat::kUnknown;
 };
 
 }  // namespace impeller

impeller/renderer/backend/gles/texture_gles.cc

@@ -130,6 +130,11 @@ struct TexImage2DData {
         external_format = GL_ALPHA;
         type = GL_UNSIGNED_BYTE;
         break;
+      case PixelFormat::kR8UNormInt:
+        internal_format = GL_RED;
+        external_format = GL_RED;
+        type = GL_UNSIGNED_BYTE;
+        break;
       case PixelFormat::kR8G8B8A8UNormInt:
       case PixelFormat::kB8G8R8A8UNormInt:
       case PixelFormat::kR8G8B8A8UNormIntSRGB:
@@ -161,7 +166,6 @@ struct TexImage2DData {
         break;
       case PixelFormat::kUnknown:
       case PixelFormat::kD32FloatS8UInt:
-      case PixelFormat::kR8UNormInt:
       case PixelFormat::kR8G8UNormInt:
       case PixelFormat::kB10G10R10XRSRGB:
       case PixelFormat::kB10G10R10XR:

impeller/renderer/backend/metal/context_mtl.mm

@@ -67,6 +67,7 @@ static bool DeviceSupportsComputeSubgroups(id<MTLDevice> device) {
       .SetSupportsComputeSubgroups(DeviceSupportsComputeSubgroups(device))
       .SetSupportsReadFromResolve(true)
       .SetSupportsDeviceTransientTextures(true)
+      .SetDefaultGlyphAtlasFormat(PixelFormat::kA8UNormInt)
       .Build();
 }
 

impeller/renderer/backend/vulkan/capabilities_vk.cc

@@ -484,4 +484,8 @@ bool CapabilitiesVK::HasOptionalDeviceExtension(
          optional_device_extensions_.end();
 }
 
+PixelFormat CapabilitiesVK::GetDefaultGlyphAtlasFormat() const {
+  return PixelFormat::kR8UNormInt;
+}
+
 }  // namespace impeller

impeller/renderer/backend/vulkan/capabilities_vk.h

@@ -100,6 +100,9 @@ class CapabilitiesVK final : public Capabilities,
   // |Capabilities|
   PixelFormat GetDefaultDepthStencilFormat() const override;
 
+  // |Capabilities|
+  PixelFormat GetDefaultGlyphAtlasFormat() const override;
+
  private:
   bool validations_enabled_ = false;
   std::map<std::string, std::set<std::string>> exts_;

impeller/renderer/backend/vulkan/debug_report_vk.cc

@@ -111,15 +111,6 @@ DebugReportVK::Result DebugReportVK::OnDebugCallback(
     return Result::kContinue;
   }
 
-  // This is a real error but we can't fix it due to our headers being too
-  // old. More more details see:
-  // https://vulkan.lunarg.com/doc/view/1.3.224.1/mac/1.3-extensions/vkspec.html#VUID-VkImageViewCreateInfo-imageViewFormatSwizzle-04465
-  // This validation error currently only trips on macOS due to the use of
-  // texture swizzles.
-  if (data->messageIdNumber == static_cast<int32_t>(0x82ae5050)) {
-    return Result::kContinue;
-  }
-
   std::vector<std::pair<std::string, std::string>> items;
 
   items.emplace_back("Severity", vk::to_string(severity));

impeller/renderer/capabilities.cc

@@ -3,6 +3,7 @@
 // found in the LICENSE file.
 
 #include "impeller/renderer/capabilities.h"
+#include "impeller/core/formats.h"
 
 namespace impeller {
 
@@ -74,10 +75,16 @@ class StandardCapabilities final : public Capabilities {
     return default_depth_stencil_format_;
   }
 
+  // |Capabilities|
   bool SupportsDeviceTransientTextures() const override {
     return supports_device_transient_textures_;
   }
 
+  // |Capabilities|
+  PixelFormat GetDefaultGlyphAtlasFormat() const override {
+    return default_glyph_atlas_format_;
+  }
+
  private:
   StandardCapabilities(bool supports_offscreen_msaa,
                        bool supports_ssbo,
@@ -91,7 +98,8 @@ class StandardCapabilities final : public Capabilities {
                        bool supports_device_transient_textures,
                        PixelFormat default_color_format,
                        PixelFormat default_stencil_format,
-                       PixelFormat default_depth_stencil_format)
+                       PixelFormat default_depth_stencil_format,
+                       PixelFormat default_glyph_atlas_format)
       : supports_offscreen_msaa_(supports_offscreen_msaa),
         supports_ssbo_(supports_ssbo),
         supports_buffer_to_texture_blits_(supports_buffer_to_texture_blits),
@@ -105,7 +113,8 @@ class StandardCapabilities final : public Capabilities {
         supports_device_transient_textures_(supports_device_transient_textures),
         default_color_format_(default_color_format),
         default_stencil_format_(default_stencil_format),
-        default_depth_stencil_format_(default_depth_stencil_format) {}
+        default_depth_stencil_format_(default_depth_stencil_format),
+        default_glyph_atlas_format_(default_glyph_atlas_format) {}
 
   friend class CapabilitiesBuilder;
 
@@ -122,6 +131,7 @@ class StandardCapabilities final : public Capabilities {
   PixelFormat default_color_format_ = PixelFormat::kUnknown;
   PixelFormat default_stencil_format_ = PixelFormat::kUnknown;
   PixelFormat default_depth_stencil_format_ = PixelFormat::kUnknown;
+  PixelFormat default_glyph_atlas_format_ = PixelFormat::kUnknown;
 
   StandardCapabilities(const StandardCapabilities&) = delete;
 
@@ -207,6 +217,12 @@ CapabilitiesBuilder& CapabilitiesBuilder::SetSupportsDeviceTransientTextures(
   return *this;
 }
 
+CapabilitiesBuilder& CapabilitiesBuilder::SetDefaultGlyphAtlasFormat(
+    PixelFormat value) {
+  default_glyph_atlas_format_ = value;
+  return *this;
+}
+
 std::unique_ptr<Capabilities> CapabilitiesBuilder::Build() {
   return std::unique_ptr<StandardCapabilities>(new StandardCapabilities(  //
       supports_offscreen_msaa_,                                           //
@@ -221,7 +237,8 @@ std::unique_ptr<Capabilities> CapabilitiesBuilder::Build() {
       supports_device_transient_textures_,                                //
       default_color_format_.value_or(PixelFormat::kUnknown),              //
       default_stencil_format_.value_or(PixelFormat::kUnknown),            //
-      default_depth_stencil_format_.value_or(PixelFormat::kUnknown)       //
+      default_depth_stencil_format_.value_or(PixelFormat::kUnknown),      //
+      default_glyph_atlas_format_.value_or(PixelFormat::kUnknown)         //
       ));
 }
 

impeller/renderer/capabilities.h

@@ -105,6 +105,12 @@ class Capabilities {
   ///         format was found.
   virtual PixelFormat GetDefaultDepthStencilFormat() const = 0;
 
+  /// @brief Returns the default pixel format for the alpha bitmap glyph atlas.
+  ///
+  ///        Some backends may use Red channel while others use grey. This
+  ///        should not have any impact
+  virtual PixelFormat GetDefaultGlyphAtlasFormat() const = 0;
+
  protected:
   Capabilities();
 
@@ -145,6 +151,8 @@ class CapabilitiesBuilder {
 
   CapabilitiesBuilder& SetSupportsDeviceTransientTextures(bool value);
 
+  CapabilitiesBuilder& SetDefaultGlyphAtlasFormat(PixelFormat value);
+
   std::unique_ptr<Capabilities> Build();
 
  private:
@@ -161,6 +169,7 @@ class CapabilitiesBuilder {
   std::optional<PixelFormat> default_color_format_ = std::nullopt;
   std::optional<PixelFormat> default_stencil_format_ = std::nullopt;
   std::optional<PixelFormat> default_depth_stencil_format_ = std::nullopt;
+  std::optional<PixelFormat> default_glyph_atlas_format_ = std::nullopt;
 
   CapabilitiesBuilder(const CapabilitiesBuilder&) = delete;
 

impeller/renderer/capabilities_unittests.cc

@@ -31,31 +31,40 @@ CAPABILITY_TEST(SupportsDeviceTransientTextures, false);
 
 TEST(CapabilitiesTest, DefaultColorFormat) {
   auto defaults = CapabilitiesBuilder().Build();
-  ASSERT_EQ(defaults->GetDefaultColorFormat(), PixelFormat::kUnknown);
+  EXPECT_EQ(defaults->GetDefaultColorFormat(), PixelFormat::kUnknown);
   auto mutated = CapabilitiesBuilder()
                      .SetDefaultColorFormat(PixelFormat::kB10G10R10A10XR)
                      .Build();
-  ASSERT_EQ(mutated->GetDefaultColorFormat(), PixelFormat::kB10G10R10A10XR);
+  EXPECT_EQ(mutated->GetDefaultColorFormat(), PixelFormat::kB10G10R10A10XR);
 }
 
 TEST(CapabilitiesTest, DefaultStencilFormat) {
   auto defaults = CapabilitiesBuilder().Build();
-  ASSERT_EQ(defaults->GetDefaultStencilFormat(), PixelFormat::kUnknown);
+  EXPECT_EQ(defaults->GetDefaultStencilFormat(), PixelFormat::kUnknown);
   auto mutated = CapabilitiesBuilder()
                      .SetDefaultStencilFormat(PixelFormat::kS8UInt)
                      .Build();
-  ASSERT_EQ(mutated->GetDefaultStencilFormat(), PixelFormat::kS8UInt);
+  EXPECT_EQ(mutated->GetDefaultStencilFormat(), PixelFormat::kS8UInt);
 }
 
 TEST(CapabilitiesTest, DefaultDepthStencilFormat) {
   auto defaults = CapabilitiesBuilder().Build();
-  ASSERT_EQ(defaults->GetDefaultDepthStencilFormat(), PixelFormat::kUnknown);
+  EXPECT_EQ(defaults->GetDefaultDepthStencilFormat(), PixelFormat::kUnknown);
   auto mutated = CapabilitiesBuilder()
                      .SetDefaultDepthStencilFormat(PixelFormat::kD32FloatS8UInt)
                      .Build();
-  ASSERT_EQ(mutated->GetDefaultDepthStencilFormat(),
+  EXPECT_EQ(mutated->GetDefaultDepthStencilFormat(),
             PixelFormat::kD32FloatS8UInt);
 }
 
+TEST(CapabilitiesTest, DefaultGlyphAtlasFormat) {
+  auto defaults = CapabilitiesBuilder().Build();
+  EXPECT_EQ(defaults->GetDefaultGlyphAtlasFormat(), PixelFormat::kUnknown);
+  auto mutated = CapabilitiesBuilder()
+                     .SetDefaultGlyphAtlasFormat(PixelFormat::kA8UNormInt)
+                     .Build();
+  EXPECT_EQ(mutated->GetDefaultGlyphAtlasFormat(), PixelFormat::kA8UNormInt);
+}
+
 }  // namespace testing
 }  // namespace impeller

impeller/renderer/testing/mocks.h

@@ -204,6 +204,7 @@ class MockCapabilities : public Capabilities {
   MOCK_METHOD(PixelFormat, GetDefaultColorFormat, (), (const, override));
   MOCK_METHOD(PixelFormat, GetDefaultStencilFormat, (), (const, override));
   MOCK_METHOD(PixelFormat, GetDefaultDepthStencilFormat, (), (const, override));
+  MOCK_METHOD(PixelFormat, GetDefaultGlyphAtlasFormat, (), (const, override));
 };
 
 class MockCommandQueue : public CommandQueue {

impeller/typographer/backends/skia/typographer_context_skia.cc

@@ -15,6 +15,8 @@
 #include "impeller/typographer/backends/skia/typeface_skia.h"
 #include "impeller/typographer/rectangle_packer.h"
 #include "impeller/typographer/typographer_context.h"
+#include "include/core/SkColor.h"
+#include "include/core/SkSize.h"
 #include "third_party/skia/include/core/SkBitmap.h"
 #include "third_party/skia/include/core/SkCanvas.h"
 #include "third_party/skia/include/core/SkFont.h"
@@ -220,7 +222,9 @@ static std::shared_ptr<SkBitmap> CreateAtlasBitmap(const GlyphAtlas& atlas,
 
   switch (atlas.GetType()) {
     case GlyphAtlas::Type::kAlphaBitmap:
-      image_info = SkImageInfo::MakeA8(atlas_size.width, atlas_size.height);
+      image_info =
+          SkImageInfo::MakeA8(SkISize{static_cast<int32_t>(atlas_size.width),
+                                      static_cast<int32_t>(atlas_size.height)});
       break;
     case GlyphAtlas::Type::kColorBitmap:
       image_info =
@@ -466,7 +470,7 @@ std::shared_ptr<GlyphAtlas> TypographerContextSkia::CreateGlyphAtlas(
   PixelFormat format;
   switch (type) {
     case GlyphAtlas::Type::kAlphaBitmap:
-      format = PixelFormat::kA8UNormInt;
+      format = context.GetCapabilities()->GetDefaultGlyphAtlasFormat();
       break;
     case GlyphAtlas::Type::kColorBitmap:
       format = PixelFormat::kR8G8B8A8UNormInt;

impeller/typographer/backends/stb/typographer_context_stb.cc

@@ -516,11 +516,12 @@ std::shared_ptr<GlyphAtlas> TypographerContextSTB::CreateGlyphAtlas(
   PixelFormat format;
   switch (type) {
     case GlyphAtlas::Type::kAlphaBitmap:
-      format = PixelFormat::kA8UNormInt;
+      format = context.GetCapabilities()->GetDefaultGlyphAtlasFormat();
       break;
     case GlyphAtlas::Type::kColorBitmap:
-      format = DISABLE_COLOR_FONT_SUPPORT ? PixelFormat::kA8UNormInt
-                                          : PixelFormat::kR8G8B8A8UNormInt;
+      format = DISABLE_COLOR_FONT_SUPPORT
+                   ? context.GetCapabilities()->GetDefaultGlyphAtlasFormat()
+                   : PixelFormat::kR8G8B8A8UNormInt;
       break;
   }
   auto texture = UploadGlyphTextureAtlas(context.GetResourceAllocator(), bitmap,

impeller/typographer/glyph_atlas.h

@@ -10,7 +10,6 @@
 #include <optional>
 #include <unordered_map>
 
-#include "flutter/fml/macros.h"
 #include "impeller/core/texture.h"
 #include "impeller/geometry/rect.h"
 #include "impeller/renderer/pipeline.h"
@@ -33,8 +32,10 @@ class GlyphAtlas {
   enum class Type {
     //--------------------------------------------------------------------------
     /// The glyphs are reprsented at their requested size using only an 8-bit
-    /// alpha channel.
+    /// color channel.
     ///
+    /// This might be backed by a grey or red single channel texture, depending
+    /// on the backend capabilities.
     kAlphaBitmap,
 
     //--------------------------------------------------------------------------

impeller/typographer/typographer_unittests.cc

@@ -117,7 +117,7 @@ TEST_P(TypographerTest, LazyAtlasTracksColor) {
 
   lazy_atlas.AddTextFrame(*frame, 1.0f);
 
-  // Creates different atlases for color and alpha bitmap.
+  // Creates different atlases for color and red bitmap.
   auto color_atlas = lazy_atlas.CreateOrGetGlyphAtlas(
       *GetContext(), GlyphAtlas::Type::kColorBitmap);