Don't waste space on an unnecessary depth buffer.

Author: chinmaygarde

impeller/aiks/canvas.cc

@@ -53,6 +53,10 @@ void Canvas::Concat(const Matrix& xformation) {
   xformation_stack_.back().xformation = xformation * GetCurrentTransformation();
 }
 
+void Canvas::ResetTransform() {
+  xformation_stack_.back().xformation = {};
+}
+
 void Canvas::Transform(const Matrix& xformation) {
   Concat(xformation);
 }

impeller/aiks/canvas.h

@@ -41,6 +41,8 @@ class Canvas {
 
   const Matrix& GetCurrentTransformation() const;
 
+  void ResetTransform();
+
   void Transform(const Matrix& xformation);
 
   void Concat(const Matrix& xformation);

impeller/display_list/display_list_dispatcher.cc

@@ -206,6 +206,11 @@ void DisplayListDispatcher::transformFullPerspective(SkScalar mxx,
   canvas_.Transform(xformation);
 }
 
+// |flutter::Dispatcher|
+void DisplayListDispatcher::transformReset() {
+  canvas_.ResetTransform();
+}
+
 static Rect ToRect(const SkRect& rect) {
   return Rect::MakeLTRB(rect.fLeft, rect.fTop, rect.fRight, rect.fBottom);
 }

impeller/display_list/display_list_dispatcher.h

@@ -118,6 +118,9 @@ class DisplayListDispatcher final : public flutter::Dispatcher {
                                 SkScalar mwz,
                                 SkScalar mwt) override;
 
+  // |flutter::Dispatcher|
+  void transformReset() override;
+
   // |flutter::Dispatcher|
   void clipRect(const SkRect& rect, SkClipOp clip_op, bool is_aa) override;
 

impeller/renderer/backend/metal/formats_mtl.h

@@ -29,6 +29,8 @@ constexpr MTLPixelFormat ToMTLPixelFormat(PixelFormat format) {
       return MTLPixelFormatDepth32Float_Stencil8;
     case PixelFormat::kR8G8B8A8UNormInt:
       return MTLPixelFormatRGBA8Unorm;
+    case PixelFormat::kS8UInt:
+      return MTLPixelFormatStencil8;
     case PixelFormat::kR8G8B8A8UNormIntSRGB:
       return MTLPixelFormatRGBA8Unorm_sRGB;
   }

impeller/renderer/backend/metal/surface_mtl.mm

@@ -61,7 +61,7 @@
   TextureDescriptor stencil0_tex;
   stencil0_tex.type = TextureType::k2DMultisample;
   stencil0_tex.sample_count = SampleCount::kCount4;
-  stencil0_tex.format = PixelFormat::kD32FloatS8UNormInt;
+  stencil0_tex.format = PixelFormat::kS8UInt;
   stencil0_tex.size = msaa_tex_desc.size;
   stencil0_tex.usage =
       static_cast<TextureUsageMask>(TextureUsage::kRenderTarget);

impeller/renderer/formats.h

@@ -50,6 +50,7 @@ enum class PixelFormat {
   kR8G8B8A8UNormIntSRGB,
   kB8G8R8A8UNormInt,
   kB8G8R8A8UNormIntSRGB,
+  kS8UInt,
   // Esoteric formats only used as render targets.
   kD32FloatS8UNormInt,
 };
@@ -166,6 +167,8 @@ constexpr size_t BytesPerPixelForPixelFormat(PixelFormat format) {
   switch (format) {
     case PixelFormat::kUnknown:
       return 0u;
+    case PixelFormat::kS8UInt:
+      return 1u;
     case PixelFormat::kR8G8B8A8UNormInt:
     case PixelFormat::kR8G8B8A8UNormIntSRGB:
     case PixelFormat::kB8G8R8A8UNormInt:

impeller/renderer/pipeline_builder.h

@@ -109,7 +109,7 @@ struct PipelineBuilder {
       StencilAttachmentDescriptor stencil0;
       stencil0.stencil_compare = CompareFunction::kLessEqual;
       desc.SetStencilAttachmentDescriptors(stencil0);
-      desc.SetStencilPixelFormat(PixelFormat::kD32FloatS8UNormInt);
+      desc.SetStencilPixelFormat(PixelFormat::kS8UInt);
     }
 
     return true;

impeller/renderer/render_target.cc

@@ -188,7 +188,7 @@ RenderTarget RenderTarget::CreateOffscreen(const Context& context,
                      static_cast<uint64_t>(TextureUsage::kShaderRead);
 
   TextureDescriptor stencil_tex0;
-  stencil_tex0.format = PixelFormat::kD32FloatS8UNormInt;
+  stencil_tex0.format = PixelFormat::kS8UInt;
   stencil_tex0.size = size;
   stencil_tex0.usage =
       static_cast<TextureUsageMask>(TextureUsage::kRenderTarget);

impeller/renderer/renderer_unittests.cc

@@ -224,7 +224,7 @@ TEST_F(RendererTest, CanRenderToTexture) {
     stencil0.store_action = StoreAction::kDontCare;
     TextureDescriptor stencil_texture_desc;
     stencil_texture_desc.size = texture_descriptor.size;
-    stencil_texture_desc.format = PixelFormat::kD32FloatS8UNormInt;
+    stencil_texture_desc.format = PixelFormat::kS8UInt;
     stencil_texture_desc.usage =
         static_cast<TextureUsageMask>(TextureUsage::kRenderTarget);
     stencil0.texture = context->GetPermanentsAllocator()->CreateTexture(