[Impeller] more efficient use of transient onscreen attachments.

impeller/renderer/backend/vulkan/surface_vk.cc

@@ -30,14 +30,13 @@ std::unique_ptr<SurfaceVK> SurfaceVK::WrapSwapchainImage(
     msaa_tex_desc.size = swapchain_image->GetSize();
     msaa_tex_desc.usage = static_cast<uint64_t>(TextureUsage::kRenderTarget);
 
-    if (!swapchain_image->HasMSAATexture()) {
+    if (!swapchain_image->GetMSAATexture()) {
       msaa_tex = context->GetResourceAllocator()->CreateTexture(msaa_tex_desc);
       msaa_tex->SetLabel("ImpellerOnscreenColorMSAA");
       if (!msaa_tex) {
         VALIDATION_LOG << "Could not allocate MSAA color texture.";
         return nullptr;
       }
-      swapchain_image->SetMSAATexture(msaa_tex);
     } else {
       msaa_tex = swapchain_image->GetMSAATexture();
     }
@@ -77,6 +76,10 @@ std::unique_ptr<SurfaceVK> SurfaceVK::WrapSwapchainImage(
 
   RenderTarget render_target_desc;
   render_target_desc.SetColorAttachment(color0, 0u);
+  render_target_desc.SetupDepthStencilAttachments(
+      *context, *context->GetResourceAllocator(), swapchain_image->GetSize(),
+      enable_msaa, "Onscreen", RenderTarget::kDefaultStencilAttachmentConfig,
+      swapchain_image->GetDepthStencilTexture());
 
   // The constructor is private. So make_unique may not be used.
   return std::unique_ptr<SurfaceVK>(

impeller/renderer/backend/vulkan/surface_vk.h

@@ -7,7 +7,6 @@
 
 #include <memory>
 
-#include "flutter/fml/macros.h"
 #include "impeller/renderer/backend/vulkan/context_vk.h"
 #include "impeller/renderer/backend/vulkan/swapchain_image_vk.h"
 #include "impeller/renderer/surface.h"

impeller/renderer/backend/vulkan/swapchain_image_vk.cc

@@ -36,15 +36,20 @@ bool SwapchainImageVK::IsValid() const {
 }
 
 std::shared_ptr<Texture> SwapchainImageVK::GetMSAATexture() const {
-  return msaa_tex_;
+  return msaa_texture_;
 }
 
-bool SwapchainImageVK::HasMSAATexture() const {
-  return msaa_tex_ != nullptr;
+std::shared_ptr<Texture> SwapchainImageVK::GetDepthStencilTexture() const {
+  return depth_stencil_texture_;
 }
 
-void SwapchainImageVK::SetMSAATexture(std::shared_ptr<Texture> msaa_tex) {
-  msaa_tex_ = std::move(msaa_tex);
+void SwapchainImageVK::SetMSAATexture(std::shared_ptr<Texture> texture) {
+  msaa_texture_ = std::move(texture);
+}
+
+void SwapchainImageVK::SetDepthStencilTexture(
+    std::shared_ptr<Texture> texture) {
+  depth_stencil_texture_ = std::move(texture);
 }
 
 PixelFormat SwapchainImageVK::GetPixelFormat() const {

impeller/renderer/backend/vulkan/swapchain_image_vk.h

@@ -33,21 +33,24 @@ class SwapchainImageVK final : public TextureSourceVK {
 
   std::shared_ptr<Texture> GetMSAATexture() const;
 
-  bool HasMSAATexture() const;
+  std::shared_ptr<Texture> GetDepthStencilTexture() const;
 
   // |TextureSourceVK|
   vk::ImageView GetImageView() const override;
 
   vk::ImageView GetRenderTargetView() const override;
 
-  void SetMSAATexture(std::shared_ptr<Texture> msaa_tex);
+  void SetMSAATexture(std::shared_ptr<Texture> texture);
+
+  void SetDepthStencilTexture(std::shared_ptr<Texture> texture);
 
   bool IsSwapchainImage() const override { return true; }
 
  private:
   vk::Image image_ = VK_NULL_HANDLE;
   vk::UniqueImageView image_view_ = {};
-  std::shared_ptr<Texture> msaa_tex_;
+  std::shared_ptr<Texture> msaa_texture_;
+  std::shared_ptr<Texture> depth_stencil_texture_;
   bool is_valid_ = false;
 
   SwapchainImageVK(const SwapchainImageVK&) = delete;

impeller/renderer/backend/vulkan/swapchain_impl_vk.cc

@@ -228,6 +228,35 @@ SwapchainImplVK::SwapchainImplVK(const std::shared_ptr<Context>& context,
   texture_desc.size = ISize::MakeWH(swapchain_info.imageExtent.width,
                                     swapchain_info.imageExtent.height);
 
+  // Allocate a single onscreen MSAA texture and Depth+Stencil Texture to
+  // be shared by all swapchain images.
+  TextureDescriptor msaa_desc;
+  msaa_desc.storage_mode = StorageMode::kDeviceTransient;
+  msaa_desc.type = TextureType::kTexture2DMultisample;
+  msaa_desc.sample_count = SampleCount::kCount4;
+  msaa_desc.format = texture_desc.format;
+  msaa_desc.size = texture_desc.size;
+  msaa_desc.usage = static_cast<uint64_t>(TextureUsage::kRenderTarget);
+
+  TextureDescriptor depth_stencil_desc;
+  depth_stencil_desc.storage_mode = StorageMode::kDeviceTransient;
+  depth_stencil_desc.type = TextureType::kTexture2DMultisample;
+  depth_stencil_desc.sample_count = SampleCount::kCount4;
+  depth_stencil_desc.format =
+      context->GetCapabilities()->GetDefaultDepthStencilFormat();
+  depth_stencil_desc.size = texture_desc.size;
+  depth_stencil_desc.usage = static_cast<uint64_t>(TextureUsage::kRenderTarget);
+
+  std::shared_ptr<Texture> msaa_texture =
+      context->GetResourceAllocator()->CreateTexture(msaa_desc);
+  std::shared_ptr<Texture> depth_stencil_texture =
+      context->GetResourceAllocator()->CreateTexture(depth_stencil_desc);
+  if (!msaa_texture || !depth_stencil_texture) {
+    VALIDATION_LOG
+        << "Failed to allocate onscreen MSAA or depth+stencil texture.";
+    return;
+  }
+
   std::vector<std::shared_ptr<SwapchainImageVK>> swapchain_images;
   for (const auto& image : images) {
     auto swapchain_image =
@@ -239,6 +268,8 @@ SwapchainImplVK::SwapchainImplVK(const std::shared_ptr<Context>& context,
       VALIDATION_LOG << "Could not create swapchain image.";
       return;
     }
+    swapchain_image->SetMSAATexture(msaa_texture);
+    swapchain_image->SetDepthStencilTexture(depth_stencil_texture);
 
     ContextVK::SetDebugName(
         vk_context.GetDevice(), swapchain_image->GetImage(),

impeller/renderer/render_target.cc

@@ -398,7 +398,8 @@ void RenderTarget::SetupDepthStencilAttachments(
     ISize size,
     bool msaa,
     const std::string& label,
-    RenderTarget::AttachmentConfig stencil_attachment_config) {
+    RenderTarget::AttachmentConfig stencil_attachment_config,
+    const std::shared_ptr<Texture>& depth_stencil_texture) {
   TextureDescriptor depth_stencil_texture_desc;
   depth_stencil_texture_desc.storage_mode =
       stencil_attachment_config.storage_mode;
@@ -412,23 +413,28 @@ void RenderTarget::SetupDepthStencilAttachments(
   depth_stencil_texture_desc.usage =
       static_cast<TextureUsageMask>(TextureUsage::kRenderTarget);
 
-  auto depth_stencil_texture =
-      allocator.CreateTexture(depth_stencil_texture_desc);
-  if (!depth_stencil_texture) {
+  std::shared_ptr<Texture> new_depth_stencil_texture =
+      depth_stencil_texture == nullptr
+          ? allocator.CreateTexture(depth_stencil_texture_desc)
+          : depth_stencil_texture;
+  FML_DCHECK(depth_stencil_texture == nullptr ||
+             depth_stencil_texture->GetTextureDescriptor() ==
+                 depth_stencil_texture_desc);
+  if (!new_depth_stencil_texture) {
     return;  // Error messages are handled by `Allocator::CreateTexture`.
   }
 
   DepthAttachment depth0;
   depth0.load_action = stencil_attachment_config.load_action;
   depth0.store_action = stencil_attachment_config.store_action;
   depth0.clear_depth = 0u;
-  depth0.texture = depth_stencil_texture;
+  depth0.texture = new_depth_stencil_texture;
 
   StencilAttachment stencil0;
   stencil0.load_action = stencil_attachment_config.load_action;
   stencil0.store_action = stencil_attachment_config.store_action;
   stencil0.clear_stencil = 0u;
-  stencil0.texture = std::move(depth_stencil_texture);
+  stencil0.texture = std::move(new_depth_stencil_texture);
 
   stencil0.texture->SetLabel(
       SPrintF("%s Depth+Stencil Texture", label.c_str()));

impeller/renderer/render_target.h

@@ -84,7 +84,8 @@ class RenderTarget final {
       bool msaa,
       const std::string& label = "Offscreen",
       RenderTarget::AttachmentConfig stencil_attachment_config =
-          RenderTarget::kDefaultStencilAttachmentConfig);
+          RenderTarget::kDefaultStencilAttachmentConfig,
+      const std::shared_ptr<Texture>& depth_stencil_texture = nullptr);
 
   SampleCount GetSampleCount() const;
 
@@ -176,15 +177,6 @@ class RenderTargetAllocator {
   virtual void End();
 
  private:
-  void SetupDepthStencilAttachments(
-      Allocator& allocator,
-      const Context& context,
-      ISize size,
-      bool msaa,
-      const std::string& label = "Offscreen",
-      RenderTarget::AttachmentConfig stencil_attachment_config =
-          RenderTarget::kDefaultStencilAttachmentConfig);
-
   std::shared_ptr<Allocator> allocator_;
 };