[Impeller] cache onscreen render targets. (#50751)

Currently we cache render pass objects to offscreen render targets only. Caching onscreen doesn't work as 1) the render targets are stored on the texture_vk object and 2) the texture_vk object is recreated for each frame (see https://github.com/flutter/engine/blob/main/impeller/renderer/backend/vulkan/surface_vk.cc#L14 ).

To make sure the render pass is cached, move the storage to the texture source.

part of flutter/flutter#141750

Author: Jonah Williams

impeller/renderer/backend/vulkan/test/mock_vulkan.cc

@@ -42,6 +42,8 @@ struct MockImage {};
 
 struct MockSemaphore {};
 
+struct MockFramebuffer {};
+
 static ISize currentImageSize = ISize{1, 1};
 
 class MockDevice final {
@@ -686,6 +688,14 @@ VkResult vkAcquireNextImageKHR(VkDevice device,
   return VK_SUCCESS;
 }
 
+VkResult vkCreateFramebuffer(VkDevice device,
+                             const VkFramebufferCreateInfo* pCreateInfo,
+                             const VkAllocationCallbacks* pAllocator,
+                             VkFramebuffer* pFramebuffer) {
+  *pFramebuffer = reinterpret_cast<VkFramebuffer>(new MockFramebuffer());
+  return VK_SUCCESS;
+}
+
 PFN_vkVoidFunction GetMockVulkanProcAddress(VkInstance instance,
                                             const char* pName) {
   if (strcmp("vkEnumerateInstanceExtensionProperties", pName) == 0) {
@@ -814,6 +824,8 @@ PFN_vkVoidFunction GetMockVulkanProcAddress(VkInstance instance,
     return (PFN_vkVoidFunction)vkDestroySurfaceKHR;
   } else if (strcmp("vkAcquireNextImageKHR", pName) == 0) {
     return (PFN_vkVoidFunction)vkAcquireNextImageKHR;
+  } else if (strcmp("vkCreateFramebuffer", pName) == 0) {
+    return (PFN_vkVoidFunction)vkCreateFramebuffer;
   }
   return noop;
 }

impeller/renderer/backend/vulkan/test/swapchain_unittests.cc

@@ -6,6 +6,7 @@
 #include "gtest/gtest.h"
 #include "impeller/renderer/backend/vulkan/swapchain_vk.h"
 #include "impeller/renderer/backend/vulkan/test/mock_vulkan.h"
+#include "impeller/renderer/backend/vulkan/texture_vk.h"
 #include "vulkan/vulkan_enums.hpp"
 
 namespace impeller {
@@ -52,5 +53,43 @@ TEST(SwapchainTest, RecreateSwapchainWhenSizeChanges) {
   EXPECT_EQ(image_b->GetSize(), expected_size);
 }
 
+TEST(SwapchainTest, CachesRenderPassOnSwapchainImage) {
+  auto const context = MockVulkanContextBuilder().Build();
+
+  auto surface = CreateSurface(*context);
+  auto swapchain =
+      SwapchainVK::Create(context, std::move(surface), ISize{1, 1});
+
+  EXPECT_TRUE(swapchain->IsValid());
+
+  // We should create 3 swapchain images with the current mock setup. However,
+  // we will only ever return the first image, so the render pass and
+  // framebuffer will be cached after one call to AcquireNextDrawable.
+  auto drawable = swapchain->AcquireNextDrawable();
+  RenderTarget render_target = drawable->GetTargetRenderPassDescriptor();
+
+  auto texture = render_target.GetRenderTargetTexture();
+  auto& texture_vk = TextureVK::Cast(*texture);
+  EXPECT_EQ(texture_vk.GetFramebuffer(), nullptr);
+  EXPECT_EQ(texture_vk.GetRenderPass(), nullptr);
+
+  auto command_buffer = context->CreateCommandBuffer();
+  auto render_pass = command_buffer->CreateRenderPass(render_target);
+
+  render_pass->EncodeCommands();
+
+  EXPECT_NE(texture_vk.GetFramebuffer(), nullptr);
+  EXPECT_NE(texture_vk.GetRenderPass(), nullptr);
+
+  {
+    auto drawable = swapchain->AcquireNextDrawable();
+    auto texture = render_target.GetRenderTargetTexture();
+    auto& texture_vk = TextureVK::Cast(*texture);
+
+    EXPECT_NE(texture_vk.GetFramebuffer(), nullptr);
+    EXPECT_NE(texture_vk.GetRenderPass(), nullptr);
+  }
+}
+
 }  // namespace testing
 }  // namespace impeller

impeller/renderer/backend/vulkan/texture_source_vk.cc

@@ -58,4 +58,22 @@ fml::Status TextureSourceVK::SetLayout(const BarrierVK& barrier) const {
   return {};
 }
 
+void TextureSourceVK::SetFramebuffer(
+    const SharedHandleVK<vk::Framebuffer>& framebuffer) {
+  framebuffer_ = framebuffer;
+}
+
+void TextureSourceVK::SetRenderPass(
+    const SharedHandleVK<vk::RenderPass>& render_pass) {
+  render_pass_ = render_pass;
+}
+
+SharedHandleVK<vk::Framebuffer> TextureSourceVK::GetFramebuffer() const {
+  return framebuffer_;
+}
+
+SharedHandleVK<vk::RenderPass> TextureSourceVK::GetRenderPass() const {
+  return render_pass_;
+}
+
 }  // namespace impeller

impeller/renderer/backend/vulkan/texture_source_vk.h

@@ -65,12 +65,38 @@ class TextureSourceVK {
   /// Whether or not this is a swapchain image.
   virtual bool IsSwapchainImage() const = 0;
 
+  /// Store the last framebuffer object used with this texture.
+  ///
+  /// This field is only set if this texture is used as the resolve texture
+  /// of a render pass. By construction, this framebuffer should be compatible
+  /// with any future render passes.
+  void SetFramebuffer(const SharedHandleVK<vk::Framebuffer>& framebuffer);
+
+  /// Store the last render pass object used with this texture.
+  ///
+  /// This field is only set if this texture is used as the resolve texture
+  /// of a render pass. By construction, this framebuffer should be compatible
+  /// with any future render passes.
+  void SetRenderPass(const SharedHandleVK<vk::RenderPass>& render_pass);
+
+  /// Retrieve the last framebuffer object used with this texture.
+  ///
+  /// May be nullptr if no previous framebuffer existed.
+  SharedHandleVK<vk::Framebuffer> GetFramebuffer() const;
+
+  /// Retrieve the last render pass object used with this texture.
+  ///
+  /// May be nullptr if no previous render pass existed.
+  SharedHandleVK<vk::RenderPass> GetRenderPass() const;
+
  protected:
   const TextureDescriptor desc_;
 
   explicit TextureSourceVK(TextureDescriptor desc);
 
  private:
+  SharedHandleVK<vk::Framebuffer> framebuffer_ = nullptr;
+  SharedHandleVK<vk::RenderPass> render_pass_ = nullptr;
   mutable RWMutex layout_mutex_;
   mutable vk::ImageLayout layout_ IPLR_GUARDED_BY(layout_mutex_) =
       vk::ImageLayout::eUndefined;

impeller/renderer/backend/vulkan/texture_vk.cc

@@ -175,20 +175,20 @@ vk::ImageView TextureVK::GetRenderTargetView() const {
 
 void TextureVK::SetFramebuffer(
     const SharedHandleVK<vk::Framebuffer>& framebuffer) {
-  framebuffer_ = framebuffer;
+  source_->SetFramebuffer(framebuffer);
 }
 
 void TextureVK::SetRenderPass(
     const SharedHandleVK<vk::RenderPass>& render_pass) {
-  render_pass_ = render_pass;
+  source_->SetRenderPass(render_pass);
 }
 
 SharedHandleVK<vk::Framebuffer> TextureVK::GetFramebuffer() const {
-  return framebuffer_;
+  return source_->GetFramebuffer();
 }
 
 SharedHandleVK<vk::RenderPass> TextureVK::GetRenderPass() const {
-  return render_pass_;
+  return source_->GetRenderPass();
 }
 
 }  // namespace impeller

impeller/renderer/backend/vulkan/texture_vk.h

@@ -73,8 +73,6 @@ class TextureVK final : public Texture, public BackendCast<TextureVK, Texture> {
  private:
   std::weak_ptr<Context> context_;
   std::shared_ptr<TextureSourceVK> source_;
-  SharedHandleVK<vk::Framebuffer> framebuffer_ = nullptr;
-  SharedHandleVK<vk::RenderPass> render_pass_ = nullptr;
 
   // |Texture|
   void SetLabel(std::string_view label) override;