Multi-encodable render passes.

engine/src/flutter/impeller/compositor/formats_metal.mm

@@ -80,19 +80,10 @@ MTLDepthStencilDescriptor* ToMTLDepthStencilDescriptor(
 static bool ConfigureRenderPassAttachment(
     RenderPassAttachment& attachment,
     MTLRenderPassAttachmentDescriptor* desc) {
-  if (!attachment) {
-    return false;
-  }
-
-  if (!desc.texture) {
-    return false;
-  }
-
   attachment.texture = std::make_shared<Texture>(desc.texture);
   attachment.load_action = FromMTLLoadAction(desc.loadAction);
   attachment.store_action = FromMTLStoreAction(desc.storeAction);
-
-  return true;
+  return attachment;
 }
 
 static ColorRenderPassAttachment FromMTLRenderPassColorAttachmentDescriptor(

engine/src/flutter/impeller/compositor/render_pass.h

@@ -68,10 +68,13 @@ class RenderPass {
 
   bool IsValid() const;
 
+  bool Encode() const;
+
  private:
   friend class CommandBuffer;
 
-  id<MTLRenderCommandEncoder> pass_ = nil;
+  id<MTLCommandBuffer> buffer_ = nil;
+  MTLRenderPassDescriptor* desc_ = nil;
   bool is_valid_ = false;
 
   RenderPass(id<MTLCommandBuffer> buffer, const RenderPassDescriptor& desc);

engine/src/flutter/impeller/compositor/render_pass.mm

@@ -114,17 +114,11 @@ MTLRenderPassDescriptor* RenderPassDescriptor::ToMTLRenderPassDescriptor()
 }
 
 RenderPass::RenderPass(id<MTLCommandBuffer> buffer,
-                       const RenderPassDescriptor& desc) {
-  auto descriptor = desc.ToMTLRenderPassDescriptor();
-  if (!descriptor) {
+                       const RenderPassDescriptor& desc)
+    : buffer_(buffer), desc_(desc.ToMTLRenderPassDescriptor()) {
+  if (!buffer_ || !desc_) {
     return;
   }
-
-  pass_ = [buffer renderCommandEncoderWithDescriptor:descriptor];
-  if (!pass_) {
-    return;
-  }
-
   is_valid_ = true;
 }
 
@@ -134,4 +128,16 @@ bool RenderPass::IsValid() const {
   return is_valid_;
 }
 
+bool RenderPass::Encode() const {
+  if (!IsValid()) {
+    return false;
+  }
+  auto pass = [buffer_ renderCommandEncoderWithDescriptor:desc_];
+  if (!pass) {
+    return false;
+  }
+  [pass endEncoding];
+  return true;
+}
+
 }  // namespace impeller

engine/src/flutter/impeller/compositor/renderer.mm

@@ -43,6 +43,13 @@ bool Renderer::Render(const Surface& surface) {
     return false;
   }
 
+  auto render_pass =
+      command_buffer->CreateRenderPass(surface.GetRenderPassDescriptor());
+  if (!render_pass) {
+    return false;
+  }
+  render_pass->Encode();
+
   ::dispatch_semaphore_wait(frames_in_flight_sema_, DISPATCH_TIME_FOREVER);
 
   command_buffer->Commit(

engine/src/flutter/impeller/compositor/surface.h

@@ -22,6 +22,8 @@ class Surface {
 
   bool IsValid() const;
 
+  const RenderPassDescriptor& GetRenderPassDescriptor() const;
+
  private:
   RenderPassDescriptor desc_;
   bool is_valid_ = false;

engine/src/flutter/impeller/compositor/surface.mm

@@ -8,8 +8,8 @@
 
 namespace impeller {
 
-Surface::Surface(RenderPassDescriptor desc) {
-  if (desc.HasColorAttachment(0)) {
+Surface::Surface(RenderPassDescriptor desc) : desc_(std::move(desc)) {
+  if (!desc_.HasColorAttachment(0)) {
     return;
   }
   is_valid_ = true;
@@ -21,4 +21,8 @@ bool Surface::IsValid() const {
   return is_valid_;
 }
 
+const RenderPassDescriptor& Surface::GetRenderPassDescriptor() const {
+  return desc_;
+}
+
 }  // namespace impeller

engine/src/flutter/impeller/compositor/texture.h

@@ -7,6 +7,7 @@
 #include <Metal/Metal.h>
 
 #include "flutter/fml/macros.h"
+#include "impeller/geometry/size.h"
 
 namespace impeller {
 
@@ -16,6 +17,8 @@ class Texture {
 
   ~Texture();
 
+  Size GetSize() const;
+
   id<MTLTexture> GetMTLTexture() const;
 
  private:

engine/src/flutter/impeller/compositor/texture.mm

@@ -10,6 +10,11 @@ Texture::Texture(id<MTLTexture> texture) : texture_(texture) {}
 
 Texture::~Texture() = default;
 
+Size Texture::GetSize() const {
+  return {static_cast<double>(texture_.width),
+          static_cast<double>(texture_.height)};
+}
+
 id<MTLTexture> Texture::GetMTLTexture() const {
   return texture_;
 }

engine/src/flutter/impeller/geometry/size.h

@@ -4,6 +4,7 @@
 
 #pragma once
 
+#include <limits>
 #include <string>
 
 namespace impeller {
@@ -16,6 +17,11 @@ struct Size {
 
   constexpr Size(double width, double height) : width(width), height(height) {}
 
+  static constexpr Size Infinite() {
+    return Size{std::numeric_limits<double>::max(),
+                std::numeric_limits<double>::max()};
+  }
+
   /*
    *  Operator overloads
    */
@@ -46,6 +52,13 @@ struct Size {
     };
   }
 
+  constexpr Size Intersection(const Size& o) const {
+    return {
+        std::min(width, o.width),
+        std::min(height, o.height),
+    };
+  }
+
   constexpr bool IsZero() const { return width * height == 0.0; }
 
   constexpr bool IsPositive() const { return width * height > 0.0; }

engine/src/flutter/impeller/host/impeller_renderer.mm

@@ -230,6 +230,7 @@ static const size_t kAlignedUniformsSize = (sizeof(Uniforms) & ~0xFF) + 0x100;
   if (!renderer_->Render(surface)) {
     FML_LOG(ERROR) << "Could not render.";
   }
+
   /// Per frame updates here
   dispatch_semaphore_wait(_inFlightSemaphore, DISPATCH_TIME_FOREVER);