Bug 1755704 - Part 2. Implement stubbed out surface related WebGPU canvas methods. r=gfx-reviewers,lsalzman

This patch hooks up the improved CanvasManagerChild::GetSnapshot method
to the WebGPU canvas context object in order to do readbacks for various
DOM facing methods such as ConvertToBlob and for Firefox Screenshots.

Differential Revision: https://phabricator.services.mozilla.com/D144309

dom/webgpu/CanvasContext.cpp

@@ -5,9 +5,11 @@
 
 #include "mozilla/dom/WebGPUBinding.h"
 #include "CanvasContext.h"
-#include "nsDisplayList.h"
+#include "gfxUtils.h"
 #include "LayerUserData.h"
+#include "nsDisplayList.h"
 #include "mozilla/dom/HTMLCanvasElement.h"
+#include "mozilla/gfx/CanvasManagerChild.h"
 #include "mozilla/layers/CompositableInProcessManager.h"
 #include "mozilla/layers/ImageDataSerializer.h"
 #include "mozilla/layers/LayersSurfaces.h"
@@ -124,5 +126,51 @@ void CanvasContext::SwapChainPresent() {
   }
 }
 
+mozilla::UniquePtr<uint8_t[]> CanvasContext::GetImageBuffer(int32_t* aFormat) {
+  gfxAlphaType any;
+  RefPtr<gfx::SourceSurface> snapshot = GetSurfaceSnapshot(&any);
+  if (!snapshot) {
+    *aFormat = 0;
+    return nullptr;
+  }
+
+  RefPtr<gfx::DataSourceSurface> dataSurface = snapshot->GetDataSurface();
+  return gfxUtils::GetImageBuffer(dataSurface, /* aIsAlphaPremultiplied */ true,
+                                  aFormat);
+}
+
+NS_IMETHODIMP CanvasContext::GetInputStream(const char* aMimeType,
+                                            const nsAString& aEncoderOptions,
+                                            nsIInputStream** aStream) {
+  gfxAlphaType any;
+  RefPtr<gfx::SourceSurface> snapshot = GetSurfaceSnapshot(&any);
+  if (!snapshot) {
+    return NS_ERROR_FAILURE;
+  }
+
+  RefPtr<gfx::DataSourceSurface> dataSurface = snapshot->GetDataSurface();
+  return gfxUtils::GetInputStream(dataSurface, /* aIsAlphaPremultiplied */ true,
+                                  aMimeType, aEncoderOptions, aStream);
+}
+
+already_AddRefed<mozilla::gfx::SourceSurface> CanvasContext::GetSurfaceSnapshot(
+    gfxAlphaType* aOutAlphaType) {
+  if (aOutAlphaType) {
+    *aOutAlphaType = gfxAlphaType::Premult;
+  }
+
+  auto* const cm = gfx::CanvasManagerChild::Get();
+  if (!cm) {
+    return nullptr;
+  }
+
+  if (!mBridge || !mBridge->IsOpen() || !mHandle) {
+    return nullptr;
+  }
+
+  return cm->GetSnapshot(cm->Id(), mBridge->Id(), mHandle, mGfxFormat,
+                         /* aPremultiply */ false, /* aYFlip */ false);
+}
+
 }  // namespace webgpu
 }  // namespace mozilla

dom/webgpu/CanvasContext.h

@@ -54,20 +54,12 @@ class CanvasContext final : public nsICanvasRenderingContextInternal,
     return NS_OK;
   }
 
-  mozilla::UniquePtr<uint8_t[]> GetImageBuffer(int32_t* aFormat) override {
-    MOZ_CRASH("todo");
-  }
+  mozilla::UniquePtr<uint8_t[]> GetImageBuffer(int32_t* aFormat) override;
   NS_IMETHOD GetInputStream(const char* aMimeType,
                             const nsAString& aEncoderOptions,
-                            nsIInputStream** aStream) override {
-    *aStream = nullptr;
-    return NS_ERROR_NOT_IMPLEMENTED;
-  }
-
+                            nsIInputStream** aStream) override;
   already_AddRefed<mozilla::gfx::SourceSurface> GetSurfaceSnapshot(
-      gfxAlphaType* aOutAlphaType) override {
-    return nullptr;
-  }
+      gfxAlphaType* aOutAlphaType) override;
 
   void SetOpaqueValueFromOpaqueAttr(bool aOpaqueAttrValue) override {}
   bool GetIsOpaque() override { return true; }