[Impeller] take advantage of native decal sampling, blend cleanups (flutter/engine#40839)

[Impeller] take advantage of native decal sampling, blend cleanups

engine/src/flutter/impeller/entity/contents/filters/blend_filter_contents.cc

@@ -118,8 +118,13 @@ static std::optional<Entity> AdvancedBlend(
     typename FS::BlendInfo blend_info;
     typename VS::FrameInfo frame_info;
 
+    auto dst_sampler_descriptor = dst_snapshot->sampler_descriptor;
+    if (renderer.GetDeviceCapabilities().SupportsDecalTileMode()) {
+      dst_sampler_descriptor.width_address_mode = SamplerAddressMode::kDecal;
+      dst_sampler_descriptor.height_address_mode = SamplerAddressMode::kDecal;
+    }
     auto dst_sampler = renderer.GetContext()->GetSamplerLibrary()->GetSampler(
-        dst_snapshot->sampler_descriptor);
+        dst_sampler_descriptor);
     FS::BindTextureSamplerDst(cmd, dst_snapshot->texture, dst_sampler);
     frame_info.dst_y_coord_scale = dst_snapshot->texture->GetYCoordScale();
     blend_info.dst_input_alpha = absorb_opacity ? dst_snapshot->opacity : 1.0;
@@ -132,8 +137,13 @@ static std::optional<Entity> AdvancedBlend(
       // binding.
       FS::BindTextureSamplerSrc(cmd, dst_snapshot->texture, dst_sampler);
     } else {
+      auto src_sampler_descriptor = src_snapshot->sampler_descriptor;
+      if (renderer.GetDeviceCapabilities().SupportsDecalTileMode()) {
+        src_sampler_descriptor.width_address_mode = SamplerAddressMode::kDecal;
+        src_sampler_descriptor.height_address_mode = SamplerAddressMode::kDecal;
+      }
       auto src_sampler = renderer.GetContext()->GetSamplerLibrary()->GetSampler(
-          src_snapshot->sampler_descriptor);
+          src_sampler_descriptor);
       blend_info.color_factor = 0;
       FS::BindTextureSamplerSrc(cmd, src_snapshot->texture, src_sampler);
       frame_info.src_y_coord_scale = src_snapshot->texture->GetYCoordScale();
@@ -220,9 +230,10 @@ static std::optional<Entity> PipelineBlend(
       frame_info.mvp = Matrix::MakeOrthographic(pass.GetRenderTargetSize()) *
                        Matrix::MakeTranslation(-coverage.origin) *
                        input->transform;
-      FS::FragInfo frag_info;
-      frag_info.texture_sampler_y_coord_scale =
+      frame_info.texture_sampler_y_coord_scale =
           input->texture->GetYCoordScale();
+
+      FS::FragInfo frag_info;
       frag_info.input_alpha = absorb_opacity ? input->opacity : 1.0;
       FS::BindFragInfo(cmd, host_buffer.EmplaceUniform(frag_info));
       VS::BindFrameInfo(cmd, host_buffer.EmplaceUniform(frame_info));
@@ -257,10 +268,8 @@ static std::optional<Entity> PipelineBlend(
 
     if (foreground_color.has_value()) {
       auto contents = std::make_shared<SolidColorContents>();
-      contents->SetGeometry(Geometry::MakeFillPath(
-          PathBuilder{}
-              .AddRect(Rect::MakeSize(pass.GetRenderTargetSize()))
-              .TakePath()));
+      contents->SetGeometry(
+          Geometry::MakeRect(Rect::MakeSize(pass.GetRenderTargetSize())));
       contents->SetColor(foreground_color.value());
 
       Entity foreground_entity;

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

@@ -128,8 +128,15 @@ bool FramebufferBlendContents::Render(const ContentContext& renderer,
 
   VS::FrameInfo frame_info;
 
+  auto src_sampler_descriptor = src_snapshot->sampler_descriptor;
+  if (!renderer.GetDeviceCapabilities().SupportsDecalTileMode()) {
+    // No known devices that support framebuffer fetch but not decal tile mode.
+    return false;
+  }
+  src_sampler_descriptor.width_address_mode = SamplerAddressMode::kDecal;
+  src_sampler_descriptor.height_address_mode = SamplerAddressMode::kDecal;
   auto src_sampler = renderer.GetContext()->GetSamplerLibrary()->GetSampler(
-      src_snapshot->sampler_descriptor);
+      src_sampler_descriptor);
   FS::BindTextureSamplerSrc(cmd, src_snapshot->texture, src_sampler);
 
   frame_info.mvp = Matrix::MakeOrthographic(pass.GetRenderTargetSize()) *

engine/src/flutter/impeller/entity/shaders/blending/advanced_blend.glsl

@@ -22,19 +22,28 @@ in vec2 v_src_texture_coords;
 
 out vec4 frag_color;
 
+vec4 Sample(sampler2D texture_sampler, vec2 texture_coords) {
+// gles 2.0 is the only backend without native decal support.
+#ifdef IMPELLER_TARGET_OPENGLES
+  return IPSampleDecal(texture_sampler, texture_coords);
+#else
+  return texture(texture_sampler, texture_coords);
+#endif
+}
+
 void main() {
-  vec4 dst_sample = IPSampleDecal(texture_sampler_dst,  // sampler
-                                  v_dst_texture_coords  // texture coordinates
-                                  ) *
+  vec4 dst_sample = Sample(texture_sampler_dst,  // sampler
+                           v_dst_texture_coords  // texture coordinates
+                           ) *
                     blend_info.dst_input_alpha;
 
   vec4 dst = IPUnpremultiply(dst_sample);
-  vec4 src = blend_info.color_factor > 0
-                 ? blend_info.color
-                 : IPUnpremultiply(IPSampleDecal(
-                       texture_sampler_src,  // sampler
-                       v_src_texture_coords  // texture coordinates
-                       ));
+  vec4 src =
+      blend_info.color_factor > 0
+          ? blend_info.color
+          : IPUnpremultiply(Sample(texture_sampler_src,  // sampler
+                                   v_src_texture_coords  // texture coordinates
+                                   ));
 
   vec4 blended = vec4(Blend(dst.rgb, src.rgb), 1) * dst.a;
 

engine/src/flutter/impeller/entity/shaders/blending/blend.frag

@@ -8,7 +8,6 @@
 uniform sampler2D texture_sampler_src;
 
 uniform FragInfo {
-  float texture_sampler_y_coord_scale;
   float input_alpha;
 }
 frag_info;
@@ -18,7 +17,6 @@ in vec2 v_texture_coords;
 out vec4 frag_color;
 
 void main() {
-  frag_color = IPSample(texture_sampler_src, v_texture_coords,
-                        frag_info.texture_sampler_y_coord_scale) *
-               frag_info.input_alpha;
+  frag_color =
+      texture(texture_sampler_src, v_texture_coords) * frag_info.input_alpha;
 }

engine/src/flutter/impeller/entity/shaders/blending/blend.vert

@@ -2,10 +2,12 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+#include <impeller/texture.glsl>
 #include <impeller/types.glsl>
 
 uniform FrameInfo {
   mat4 mvp;
+  float texture_sampler_y_coord_scale;
 }
 frame_info;
 
@@ -16,5 +18,6 @@ out vec2 v_texture_coords;
 
 void main() {
   gl_Position = frame_info.mvp * vec4(vertices, 0.0, 1.0);
-  v_texture_coords = texture_coords;
+  v_texture_coords =
+      IPRemapCoords(texture_coords, frame_info.texture_sampler_y_coord_scale);
 }

engine/src/flutter/impeller/entity/shaders/blending/ios/framebuffer_blend.glsl

@@ -34,9 +34,9 @@ void main() {
   vec4 dst_sample = ReadDestination();
   vec4 dst = IPUnpremultiply(dst_sample);
   vec4 src =
-      IPUnpremultiply(IPSampleDecal(texture_sampler_src,  // sampler
-                                    v_src_texture_coords  // texture coordinates
-                                    ));
+      IPUnpremultiply(texture(texture_sampler_src,  // sampler
+                              v_src_texture_coords  // texture coordinates
+                              ));
 
   vec4 blended = vec4(Blend(dst.rgb, src.rgb), 1) * dst.a;