Bug 1948175 - Add byte stride delivery to PCanvasManagerChild::SendGetSnapshot() r=gfx-reviewers,lsalzman

On macOS, ComputeRGBStride() uses alignment of 32 bytes.

Differential Revision: https://phabricator.services.mozilla.com/D238150

Author: sotaro

dom/canvas/WebGLIpdl.h

@@ -127,12 +127,14 @@ struct IPDLParamTraits<mozilla::webgl::FrontBufferSnapshotIpc> final {
 
   static void Write(IPC::MessageWriter* const writer, IProtocol* actor, T& in) {
     WriteParam(writer, in.surfSize);
+    WriteParam(writer, in.byteStride);
     WriteIPDLParam(writer, actor, std::move(in.shmem));
   }
 
   static bool Read(IPC::MessageReader* const reader, IProtocol* actor,
                    T* const out) {
     return ReadParam(reader, &out->surfSize) &&
+           ReadParam(reader, &out->byteStride) &&
            ReadIPDLParam(reader, actor, &out->shmem);
   }
 };

dom/canvas/WebGLParent.cpp

@@ -147,14 +147,15 @@ IPCResult WebGLParent::GetFrontBufferSnapshot(
     if (maybeSize) {
       const auto& surfSize = *maybeSize;
       const auto byteSize = 4 * surfSize.x * surfSize.y;
+      const auto byteStride = 4 * surfSize.x;
 
       auto shmem = webgl::RaiiShmem::Alloc(aProtocol, byteSize);
       if (!shmem) {
         NS_WARNING("Failed to alloc shmem for RecvGetFrontBufferSnapshot.");
         return false;
       }
       const auto range = shmem.ByteRange();
-      *ret = {surfSize, Some(shmem.Extract())};
+      *ret = {surfSize, byteStride, Some(shmem.Extract())};
 
       if (!mHost->FrontBufferSnapshotInto(Some(range))) {
         gfxCriticalNote << "WebGLParent::RecvGetFrontBufferSnapshot: "

dom/canvas/WebGLTypes.h

@@ -894,6 +894,7 @@ struct GetUniformData final {
 
 struct FrontBufferSnapshotIpc final {
   uvec2 surfSize = {};
+  size_t byteStride = 0;
   Maybe<mozilla::ipc::Shmem> shmem = {};
 };
 

dom/webgpu/ipc/WebGPUParent.cpp

@@ -1247,7 +1247,8 @@ static void ReadbackSnapshotCallback(uint8_t* userdata,
 
 ipc::IPCResult WebGPUParent::GetFrontBufferSnapshot(
     IProtocol* aProtocol, const layers::RemoteTextureOwnerId& aOwnerId,
-    const RawId& aCommandEncoderId, Maybe<Shmem>& aShmem, gfx::IntSize& aSize) {
+    const RawId& aCommandEncoderId, Maybe<Shmem>& aShmem, gfx::IntSize& aSize,
+    uint32_t& aByteStride) {
   const auto& lookup = mPresentationDataMap.find(aOwnerId);
   if (lookup == mPresentationDataMap.end()) {
     MOZ_ASSERT_UNREACHABLE("unexpected to be called");
@@ -1259,6 +1260,7 @@ ipc::IPCResult WebGPUParent::GetFrontBufferSnapshot(
   aSize = data->mDesc.size();
   uint32_t stride = layers::ImageDataSerializer::ComputeRGBStride(
       data->mDesc.format(), aSize.width);
+  aByteStride = stride;
   uint32_t len = data->mDesc.size().height * stride;
   Shmem shmem;
   if (!AllocShmem(len, &shmem)) {

dom/webgpu/ipc/WebGPUParent.h

@@ -135,8 +135,8 @@ class WebGPUParent final : public PWebGPUParent, public SupportsWeakPtr {
 
   ipc::IPCResult GetFrontBufferSnapshot(
       IProtocol* aProtocol, const layers::RemoteTextureOwnerId& aOwnerId,
-      const RawId& aCommandEncoderId, Maybe<Shmem>& aShmem,
-      gfx::IntSize& aSize);
+      const RawId& aCommandEncoderId, Maybe<Shmem>& aShmem, gfx::IntSize& aSize,
+      uint32_t& aByteStride);
 
   void ActorDestroy(ActorDestroyReason aWhy) override;
 

gfx/ipc/CanvasManagerChild.cpp

@@ -255,7 +255,7 @@ already_AddRefed<DataSourceSurface> CanvasManagerChild::GetSnapshot(
   }
 
   IntSize size(res.surfSize.x, res.surfSize.y);
-  CheckedInt32 stride = CheckedInt32(size.width) * sizeof(uint32_t);
+  CheckedInt32 stride = CheckedInt32(res.byteStride);
   if (!stride.isValid()) {
     return nullptr;
   }

gfx/ipc/CanvasManagerParent.cpp

@@ -221,13 +221,15 @@ mozilla::ipc::IPCResult CanvasManagerParent::RecvGetSnapshot(
       if (aCommandEncoderId.isNothing()) {
         return IPC_FAIL(this, "invalid CommandEncoderId");
       }
+      uint32_t stride = 0;
       mozilla::ipc::IPCResult rv = webgpu->GetFrontBufferSnapshot(
-          this, *aOwnerId, *aCommandEncoderId, buffer.shmem, size);
+          this, *aOwnerId, *aCommandEncoderId, buffer.shmem, size, stride);
       if (!rv) {
         return rv;
       }
       buffer.surfSize.x = static_cast<uint32_t>(size.width);
       buffer.surfSize.y = static_cast<uint32_t>(size.height);
+      buffer.byteStride = stride;
     } break;
     default:
       return IPC_FAIL(this, "unsupported protocol");