[Impeller] drawVertices uber shader. (#52315)

In order to land #52303 , we need to finally fix the advanced blend draw vertices combo. Right now a ColorFilter is used for advanced blends which doesn't work if there are overlapping vertices.

See also: flutter/flutter#145707

The issue was fixed for drawVertices/drawAtlas pipeline blends using the porterduff shader. This extends this to advanced blends, but since drawVertices/atlas with an advanced blend is uncommon and  because we don't 15 new shader variants, just add one special uber shader.

Part of flutter/flutter#131345

Author: jonahwilliams

ci/licenses_golden/licenses_flutter

@@ -40377,6 +40377,8 @@ ORIGIN: ../../../flutter/impeller/entity/shaders/blending/framebuffer_blend.frag
 ORIGIN: ../../../flutter/impeller/entity/shaders/blending/framebuffer_blend.vert + ../../../flutter/LICENSE
 ORIGIN: ../../../flutter/impeller/entity/shaders/blending/porter_duff_blend.frag + ../../../flutter/LICENSE
 ORIGIN: ../../../flutter/impeller/entity/shaders/blending/porter_duff_blend.vert + ../../../flutter/LICENSE
+ORIGIN: ../../../flutter/impeller/entity/shaders/blending/vertices_uber.frag + ../../../flutter/LICENSE
+ORIGIN: ../../../flutter/impeller/entity/shaders/blending/vertices_uber.vert + ../../../flutter/LICENSE
 ORIGIN: ../../../flutter/impeller/entity/shaders/border_mask_blur.frag + ../../../flutter/LICENSE
 ORIGIN: ../../../flutter/impeller/entity/shaders/border_mask_blur.vert + ../../../flutter/LICENSE
 ORIGIN: ../../../flutter/impeller/entity/shaders/clip.frag + ../../../flutter/LICENSE
@@ -43257,6 +43259,8 @@ FILE: ../../../flutter/impeller/entity/shaders/blending/framebuffer_blend.frag
 FILE: ../../../flutter/impeller/entity/shaders/blending/framebuffer_blend.vert
 FILE: ../../../flutter/impeller/entity/shaders/blending/porter_duff_blend.frag
 FILE: ../../../flutter/impeller/entity/shaders/blending/porter_duff_blend.vert
+FILE: ../../../flutter/impeller/entity/shaders/blending/vertices_uber.frag
+FILE: ../../../flutter/impeller/entity/shaders/blending/vertices_uber.vert
 FILE: ../../../flutter/impeller/entity/shaders/border_mask_blur.frag
 FILE: ../../../flutter/impeller/entity/shaders/border_mask_blur.vert
 FILE: ../../../flutter/impeller/entity/shaders/clip.frag

impeller/aiks/aiks_unittests.cc

@@ -2773,6 +2773,38 @@ TEST_P(AiksTest, VerticesGeometryColorUVPositionData) {
   ASSERT_TRUE(OpenPlaygroundHere(canvas.EndRecordingAsPicture()));
 }
 
+TEST_P(AiksTest, VerticesGeometryColorUVPositionDataAdvancedBlend) {
+  Canvas canvas;
+  Paint paint;
+  auto texture = CreateTextureForFixture("table_mountain_nx.png");
+
+  paint.color_source =
+      ColorSource::MakeImage(texture, Entity::TileMode::kClamp,
+                             Entity::TileMode::kClamp, {}, Matrix());
+
+  auto vertices = {
+      Point(0, 0),
+      Point(texture->GetSize().width, 0),
+      Point(0, texture->GetSize().height),
+      Point(texture->GetSize().width, 0),
+      Point(0, 0),
+      Point(texture->GetSize().width, texture->GetSize().height),
+  };
+  std::vector<uint16_t> indices = {};
+  std::vector<Point> texture_coordinates = {};
+  std::vector<Color> vertex_colors = {
+      Color::Red().WithAlpha(0.5),   Color::Blue().WithAlpha(0.5),
+      Color::Green().WithAlpha(0.5), Color::Red().WithAlpha(0.5),
+      Color::Blue().WithAlpha(0.5),  Color::Green().WithAlpha(0.5),
+  };
+  auto geometry = std::make_shared<VerticesGeometry>(
+      vertices, indices, texture_coordinates, vertex_colors,
+      Rect::MakeLTRB(0, 0, 1, 1), VerticesGeometry::VertexMode::kTriangles);
+
+  canvas.DrawVertices(geometry, BlendMode::kColorBurn, paint);
+  ASSERT_TRUE(OpenPlaygroundHere(canvas.EndRecordingAsPicture()));
+}
+
 TEST_P(AiksTest, MatrixImageFilterMagnify) {
   Canvas canvas;
   canvas.Scale(GetContentScale());

impeller/aiks/canvas.cc

@@ -938,23 +938,21 @@ void Canvas::DrawVertices(const std::shared_ptr<VerticesGeometry>& vertices,
 
   // If there is are per-vertex colors, an image, and the blend mode
   // is simple we can draw without a sub-renderpass.
-  if (blend_mode <= BlendMode::kModulate && vertices->HasVertexColors()) {
-    if (std::optional<ImageData> maybe_image_data =
-            GetImageColorSourceData(paint.color_source)) {
-      const ImageData& image_data = maybe_image_data.value();
-      auto contents = std::make_shared<VerticesSimpleBlendContents>();
-      contents->SetBlendMode(blend_mode);
-      contents->SetAlpha(paint.color.alpha);
-      contents->SetGeometry(vertices);
-
-      contents->SetEffectTransform(image_data.effect_transform);
-      contents->SetTexture(image_data.texture);
-      contents->SetTileMode(image_data.x_tile_mode, image_data.y_tile_mode);
-
-      entity.SetContents(paint.WithFilters(std::move(contents)));
-      AddRenderEntityToCurrentPass(std::move(entity));
-      return;
-    }
+  if (std::optional<ImageData> maybe_image_data =
+          GetImageColorSourceData(paint.color_source)) {
+    const ImageData& image_data = maybe_image_data.value();
+    auto contents = std::make_shared<VerticesSimpleBlendContents>();
+    contents->SetBlendMode(blend_mode);
+    contents->SetAlpha(paint.color.alpha);
+    contents->SetGeometry(vertices);
+
+    contents->SetEffectTransform(image_data.effect_transform);
+    contents->SetTexture(image_data.texture);
+    contents->SetTileMode(image_data.x_tile_mode, image_data.y_tile_mode);
+
+    entity.SetContents(paint.WithFilters(std::move(contents)));
+    AddRenderEntityToCurrentPass(std::move(entity));
+    return;
   }
 
   auto src_paint = paint;

impeller/entity/BUILD.gn

@@ -52,6 +52,8 @@ impeller_shaders("entity_shaders") {
     "shaders/filters/linear_to_srgb_filter.frag",
     "shaders/filters/morphology_filter.frag",
     "shaders/filters/morphology_filter.vert",
+    "shaders/blending/vertices_uber.frag",
+    "shaders/blending/vertices_uber.vert",
   ]
 
   if (impeller_debug) {

impeller/entity/contents/content_context.cc

@@ -445,6 +445,7 @@ ContentContext::ContentContext(
   yuv_to_rgb_filter_pipelines_.CreateDefault(*context_, options_trianglestrip);
   porter_duff_blend_pipelines_.CreateDefault(*context_, options_trianglestrip,
                                              {supports_decal});
+  vertices_uber_shader_.CreateDefault(*context_, options);
   // GLES only shader that is unsupported on macOS.
 #if defined(IMPELLER_ENABLE_OPENGLES) && !defined(FML_OS_MACOSX)
   if (GetContext()->GetBackendType() == Context::BackendType::kOpenGLES) {

impeller/entity/contents/content_context.h

@@ -81,6 +81,9 @@
 #include "impeller/entity/framebuffer_blend.frag.h"
 #include "impeller/entity/framebuffer_blend.vert.h"
 
+#include "impeller/entity/vertices_uber.frag.h"
+#include "impeller/entity/vertices_uber.vert.h"
+
 #ifdef IMPELLER_ENABLE_OPENGLES
 #include "impeller/entity/tiled_texture_fill_external.frag.h"
 #endif  // IMPELLER_ENABLE_OPENGLES
@@ -251,6 +254,10 @@ using FramebufferBlendSoftLightPipeline =
     RenderPipelineHandle<FramebufferBlendVertexShader,
                          FramebufferBlendFragmentShader>;
 
+/// Draw Vertices/Atlas Uber Shader
+using VerticesUberShader =
+    RenderPipelineHandle<VerticesUberVertexShader, VerticesUberFragmentShader>;
+
 /// Geometry Pipelines
 using PointsComputeShaderPipeline = ComputePipelineBuilder<PointsComputeShader>;
 using UvComputeShaderPipeline = ComputePipelineBuilder<UvComputeShader>;
@@ -721,6 +728,11 @@ class ContentContext {
     return GetPipeline(framebuffer_blend_softlight_pipelines_, opts);
   }
 
+  std::shared_ptr<Pipeline<PipelineDescriptor>> GetDrawVerticesUberShader(
+      ContentContextOptions opts) const {
+    return GetPipeline(vertices_uber_shader_, opts);
+  }
+
   std::shared_ptr<Pipeline<ComputePipelineDescriptor>> GetPointComputePipeline()
       const {
     FML_DCHECK(GetDeviceCapabilities().SupportsCompute());
@@ -995,6 +1007,7 @@ class ContentContext {
       framebuffer_blend_screen_pipelines_;
   mutable Variants<FramebufferBlendSoftLightPipeline>
       framebuffer_blend_softlight_pipelines_;
+  mutable Variants<VerticesUberShader> vertices_uber_shader_;
   mutable std::shared_ptr<Pipeline<ComputePipelineDescriptor>>
       point_field_compute_pipelines_;
   mutable std::shared_ptr<Pipeline<ComputePipelineDescriptor>>

impeller/entity/contents/vertices_contents.cc

@@ -243,7 +243,6 @@ void VerticesSimpleBlendContents::SetAlpha(Scalar alpha) {
 }
 
 void VerticesSimpleBlendContents::SetBlendMode(BlendMode blend_mode) {
-  FML_DCHECK(blend_mode <= BlendMode::kModulate);
   blend_mode_ = blend_mode;
 }
 
@@ -275,11 +274,22 @@ bool VerticesSimpleBlendContents::Render(const ContentContext& renderer,
                                          const Entity& entity,
                                          RenderPass& pass) const {
   FML_DCHECK(texture_);
-  FML_DCHECK(geometry_->HasVertexColors());
+  BlendMode blend_mode = blend_mode_;
+  if (!geometry_->HasVertexColors()) {
+    blend_mode = BlendMode::kSource;
+  }
+
+  auto dst_sampler_descriptor = descriptor_;
+  dst_sampler_descriptor.width_address_mode =
+      TileModeToAddressMode(tile_mode_x_, renderer.GetDeviceCapabilities())
+          .value_or(SamplerAddressMode::kClampToEdge);
+  dst_sampler_descriptor.height_address_mode =
+      TileModeToAddressMode(tile_mode_y_, renderer.GetDeviceCapabilities())
+          .value_or(SamplerAddressMode::kClampToEdge);
 
-  // Simple Porter-Duff blends can be accomplished without a sub renderpass.
-  using VS = PorterDuffBlendPipeline::VertexShader;
-  using FS = PorterDuffBlendPipeline::FragmentShader;
+  const std::unique_ptr<const Sampler>& dst_sampler =
+      renderer.GetContext()->GetSamplerLibrary()->GetSampler(
+          dst_sampler_descriptor);
 
   GeometryResult geometry_result = geometry_->GetPositionUVColorBuffer(
       Rect::MakeSize(texture_->GetSize()), inverse_matrix_, renderer, entity,
@@ -289,53 +299,76 @@ bool VerticesSimpleBlendContents::Render(const ContentContext& renderer,
   }
   FML_DCHECK(geometry_result.mode == GeometryResult::Mode::kNormal);
 
+  if (blend_mode <= Entity::kLastPipelineBlendMode) {
+    using VS = PorterDuffBlendPipeline::VertexShader;
+    using FS = PorterDuffBlendPipeline::FragmentShader;
+
+#ifdef IMPELLER_DEBUG
+    pass.SetCommandLabel(SPrintF("DrawVertices Porterduff Blend (%s)",
+                                 BlendModeToString(blend_mode)));
+#endif  // IMPELLER_DEBUG
+    pass.SetVertexBuffer(std::move(geometry_result.vertex_buffer));
+
+    auto options = OptionsFromPassAndEntity(pass, entity);
+    options.primitive_type = geometry_result.type;
+    pass.SetPipeline(renderer.GetPorterDuffBlendPipeline(options));
+
+    FS::BindTextureSamplerDst(pass, texture_, dst_sampler);
+
+    VS::FrameInfo frame_info;
+    FS::FragInfo frag_info;
+
+    frame_info.texture_sampler_y_coord_scale = texture_->GetYCoordScale();
+    frame_info.mvp = geometry_result.transform;
+
+    frag_info.output_alpha = alpha_;
+    frag_info.input_alpha = 1.0;
+
+    auto inverted_blend_mode =
+        InvertPorterDuffBlend(blend_mode).value_or(BlendMode::kSource);
+    auto blend_coefficients =
+        kPorterDuffCoefficients[static_cast<int>(inverted_blend_mode)];
+    frag_info.src_coeff = blend_coefficients[0];
+    frag_info.src_coeff_dst_alpha = blend_coefficients[1];
+    frag_info.dst_coeff = blend_coefficients[2];
+    frag_info.dst_coeff_src_alpha = blend_coefficients[3];
+    frag_info.dst_coeff_src_color = blend_coefficients[4];
+    // Only used on devices that do not natively support advanced blends.
+    frag_info.tmx = static_cast<int>(tile_mode_x_);
+    frag_info.tmy = static_cast<int>(tile_mode_y_);
+
+    auto& host_buffer = renderer.GetTransientsBuffer();
+    FS::BindFragInfo(pass, host_buffer.EmplaceUniform(frag_info));
+    VS::BindFrameInfo(pass, host_buffer.EmplaceUniform(frame_info));
+
+    return pass.Draw().ok();
+  }
+
+  using VS = VerticesUberShader::VertexShader;
+  using FS = VerticesUberShader::FragmentShader;
+
 #ifdef IMPELLER_DEBUG
-  pass.SetCommandLabel(SPrintF("DrawVertices Porterduff Blend (%s)",
-                               BlendModeToString(blend_mode_)));
+  pass.SetCommandLabel(SPrintF("DrawVertices Advanced Blend (%s)",
+                               BlendModeToString(blend_mode)));
 #endif  // IMPELLER_DEBUG
   pass.SetVertexBuffer(std::move(geometry_result.vertex_buffer));
 
   auto options = OptionsFromPassAndEntity(pass, entity);
   options.primitive_type = geometry_result.type;
-  pass.SetPipeline(renderer.GetPorterDuffBlendPipeline(options));
-
-  auto dst_sampler_descriptor = descriptor_;
-  dst_sampler_descriptor.width_address_mode =
-      TileModeToAddressMode(tile_mode_x_, renderer.GetDeviceCapabilities())
-          .value_or(SamplerAddressMode::kClampToEdge);
-  dst_sampler_descriptor.height_address_mode =
-      TileModeToAddressMode(tile_mode_y_, renderer.GetDeviceCapabilities())
-          .value_or(SamplerAddressMode::kClampToEdge);
+  pass.SetPipeline(renderer.GetDrawVerticesUberShader(options));
+  FS::BindTextureSampler(pass, texture_, dst_sampler);
 
-  const std::unique_ptr<const Sampler>& dst_sampler =
-      renderer.GetContext()->GetSamplerLibrary()->GetSampler(
-          dst_sampler_descriptor);
-  FS::BindTextureSamplerDst(pass, texture_, dst_sampler);
-
-  FS::FragInfo frag_info;
   VS::FrameInfo frame_info;
+  FS::FragInfo frag_info;
 
   frame_info.texture_sampler_y_coord_scale = texture_->GetYCoordScale();
-  frag_info.output_alpha = alpha_;
-  frag_info.input_alpha = 1.0;
-
-  auto inverted_blend_mode =
-      InvertPorterDuffBlend(blend_mode_).value_or(BlendMode::kSource);
-  auto blend_coefficients =
-      kPorterDuffCoefficients[static_cast<int>(inverted_blend_mode)];
-  frag_info.src_coeff = blend_coefficients[0];
-  frag_info.src_coeff_dst_alpha = blend_coefficients[1];
-  frag_info.dst_coeff = blend_coefficients[2];
-  frag_info.dst_coeff_src_alpha = blend_coefficients[3];
-  frag_info.dst_coeff_src_color = blend_coefficients[4];
+  frame_info.mvp = geometry_result.transform;
+  frag_info.alpha = alpha_;
+  frag_info.blend_mode = static_cast<int>(blend_mode);
 
   auto& host_buffer = renderer.GetTransientsBuffer();
   FS::BindFragInfo(pass, host_buffer.EmplaceUniform(frag_info));
-
-  frame_info.mvp = geometry_result.transform;
-
-  auto uniform_view = host_buffer.EmplaceUniform(frame_info);
-  VS::BindFrameInfo(pass, uniform_view);
+  VS::BindFrameInfo(pass, host_buffer.EmplaceUniform(frame_info));
 
   return pass.Draw().ok();
 }

impeller/entity/contents/vertices_contents.h

@@ -108,8 +108,8 @@ class VerticesUVContents final : public Contents {
   VerticesUVContents& operator=(const VerticesUVContents&) = delete;
 };
 
-/// A vertices contents for per-color vertices + texture and porter duff
-/// blended.
+/// A vertices contents for (optional) per-color vertices + texture and any
+/// blend mode.
 class VerticesSimpleBlendContents final : public Contents {
  public:
   VerticesSimpleBlendContents();

impeller/entity/geometry/vertices_geometry.cc

@@ -256,6 +256,7 @@ GeometryResult VerticesGeometry::GetPositionUVColorBuffer(
   auto uv_transform =
       texture_coverage.GetNormalizingTransform() * effect_transform;
   auto has_texture_coordinates = HasTextureCoordinates();
+  auto has_colors = HasVertexColors();
 
   size_t total_vtx_bytes = vertices_.size() * sizeof(VS::PerVertexData);
   auto vertex_buffer = renderer.GetTransientsBuffer().Emplace(
@@ -274,7 +275,7 @@ GeometryResult VerticesGeometry::GetPositionUVColorBuffer(
               .texture_coords =
                   Point(std::clamp(uv.x, 0.0f, 1.0f - kEhCloseEnough),
                         std::clamp(uv.y, 0.0f, 1.0f - kEhCloseEnough)),
-              .color = colors_[i],
+              .color = has_colors ? colors_[i] : Color::BlackTransparent(),
           };
           std::memcpy(vtx_contents++, &vertex_data, sizeof(VS::PerVertexData));
         }

impeller/entity/shaders/blending/porter_duff_blend.frag

@@ -21,6 +21,8 @@ uniform FragInfo {
   float16_t dst_coeff_src_color;
   float16_t input_alpha;
   float16_t output_alpha;
+  float tmx;
+  float tmy;
 }
 frag_info;
 
@@ -29,16 +31,20 @@ in f16vec4 v_color;
 
 out f16vec4 frag_color;
 
-f16vec4 Sample(f16sampler2D texture_sampler, vec2 texture_coords) {
+f16vec4 Sample(f16sampler2D texture_sampler,
+               vec2 texture_coords,
+               float tmx,
+               float tmy) {
   if (supports_decal > 0.0) {
     return texture(texture_sampler, texture_coords);
   }
-  return IPHalfSampleDecal(texture_sampler, texture_coords);
+  return IPHalfSampleWithTileMode(texture_sampler, texture_coords, tmx, tmy);
 }
 
 void main() {
-  f16vec4 dst =
-      texture(texture_sampler_dst, v_texture_coords) * frag_info.input_alpha;
+  f16vec4 dst = Sample(texture_sampler_dst, v_texture_coords, frag_info.tmx,
+                       frag_info.tmy) *
+                frag_info.input_alpha;
   f16vec4 src = v_color;
   frag_color =
       src * (frag_info.src_coeff + dst.a * frag_info.src_coeff_dst_alpha) +

impeller/entity/shaders/blending/vertices_uber.frag

@@ -0,0 +1,33 @@
+// 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 <impeller/blending.glsl>
+#include <impeller/types.glsl>
+#include "blend_select.glsl"
+
+uniform FragInfo {
+  float16_t alpha;
+  float16_t blend_mode;
+}
+frag_info;
+
+uniform f16sampler2D texture_sampler;
+
+in highp vec2 v_texture_coords;
+in mediump f16vec4 v_color;
+
+out f16vec4 frag_color;
+
+// A shader that implements the required src/dst blending for drawVertices and
+// drawAtlas advanced blends without requiring an offscreen render pass. This is
+// done in a single shader to reduce the permutations of PSO needed at runtime
+// for rarely used features.
+void main() {
+  f16vec4 dst = IPHalfUnpremultiply(v_color);
+  f16vec4 src = IPHalfUnpremultiply(texture(texture_sampler, v_texture_coords));
+  f16vec3 blend_result =
+      AdvancedBlend(dst.rgb, src.rgb, int(frag_info.blend_mode - 14.0));
+  frag_color = IPApplyBlendedColor(dst, src, blend_result);
+  frag_color *= frag_info.alpha;
+}