Create 1x1 Dummy Texture For Single-Plane External Textures

Creates a 1x1x1 dummy texture that will be bound, but unused to shaders
that use external textures. It is expected that a special texture type
will be introduced and used in the future to optimize backends that
allow null bindings.

Bug: dawn:1082
Change-Id: I0c49f58f6a725290ec9b73b09578c0f85e5b38d7
Reviewed-on: https://dawn-review.googlesource.com/c/dawn/+/78940
Reviewed-by: Corentin Wallez <cwallez@chromium.org>
Reviewed-by: Austin Eng <enga@chromium.org>
Commit-Queue: Brandon1 Jones <brandon1.jones@intel.com>

src/dawn_native/ExternalTexture.cpp

@@ -125,7 +125,31 @@ namespace dawn::native {
                                                const ExternalTextureDescriptor* descriptor) {
         // Store any passed in TextureViews associated with individual planes.
         mTextureViews[0] = descriptor->plane0;
-        mTextureViews[1] = descriptor->plane1;
+
+        if (descriptor->plane1) {
+            mTextureViews[1] = descriptor->plane1;
+        } else {
+            TextureDescriptor textureDesc;
+            textureDesc.dimension = wgpu::TextureDimension::e2D;
+            textureDesc.format = wgpu::TextureFormat::RGBA8Unorm;
+            textureDesc.label = "Dawn_External_Texture_Dummy_Texture";
+            textureDesc.size = {1, 1, 1};
+            textureDesc.usage = wgpu::TextureUsage::TextureBinding;
+
+            DAWN_TRY_ASSIGN(mDummyTexture, device->CreateTexture(&textureDesc));
+
+            TextureViewDescriptor textureViewDesc;
+            textureViewDesc.arrayLayerCount = 1;
+            textureViewDesc.aspect = wgpu::TextureAspect::All;
+            textureViewDesc.baseArrayLayer = 0;
+            textureViewDesc.dimension = wgpu::TextureViewDimension::e2D;
+            textureViewDesc.format = wgpu::TextureFormat::RGBA8Unorm;
+            textureViewDesc.label = "Dawn_External_Texture_Dummy_Texture_View";
+            textureViewDesc.mipLevelCount = 1;
+
+            DAWN_TRY_ASSIGN(mTextureViews[1],
+                            device->CreateTextureView(mDummyTexture.Get(), &textureViewDesc));
+        }
 
         // We must create a buffer to store parameters needed by a shader that operates on this
         // external texture.

src/dawn_native/ExternalTexture.h

@@ -65,6 +65,7 @@ namespace dawn::native {
         ExternalTextureBase(DeviceBase* device, const ExternalTextureDescriptor* descriptor);
         ExternalTextureBase(DeviceBase* device, ObjectBase::ErrorTag tag);
 
+        Ref<TextureBase> mDummyTexture;
         Ref<BufferBase> mParamsBuffer;
         std::array<Ref<TextureViewBase>, kMaxPlanesPerFormat> mTextureViews;
 

src/dawn_native/PassResourceUsageTracker.cpp

@@ -131,9 +131,6 @@ namespace dawn::native {
                     const std::array<Ref<TextureViewBase>, kMaxPlanesPerFormat>& textureViews =
                         externalTexture->GetTextureViews();
 
-                    // Only single-plane formats are supported right now, so assert only one
-                    // view exists.
-                    ASSERT(textureViews[1].Get() == nullptr);
                     ASSERT(textureViews[2].Get() == nullptr);
 
                     mExternalTextureUsages.insert(externalTexture);
@@ -205,9 +202,6 @@ namespace dawn::native {
                     const std::array<Ref<TextureViewBase>, kMaxPlanesPerFormat>& textureViews =
                         externalTexture->GetTextureViews();
 
-                    // Only single-plane formats are supported right now, so assert only one
-                    // view exists.
-                    ASSERT(textureViews[1].Get() == nullptr);
                     ASSERT(textureViews[2].Get() == nullptr);
 
                     mUsage.referencedExternalTextures.insert(externalTexture);

src/dawn_native/d3d12/BindGroupD3D12.cpp

@@ -180,9 +180,6 @@ namespace dawn::native::d3d12 {
                     const std::array<Ref<TextureViewBase>, kMaxPlanesPerFormat>& views =
                         GetBindingAsExternalTexture(bindingIndex)->GetTextureViews();
 
-                    // Only single-plane formats are supported right now, so assert only one view
-                    // exists.
-                    ASSERT(views[1].Get() == nullptr);
                     ASSERT(views[2].Get() == nullptr);
 
                     auto& srv = ToBackend(views[0])->GetSRVDescriptor();

src/dawn_native/metal/CommandBufferMTL.mm

@@ -495,9 +495,6 @@ namespace dawn::native::metal {
                             const std::array<Ref<TextureViewBase>, kMaxPlanesPerFormat>& views =
                                 group->GetBindingAsExternalTexture(bindingIndex)->GetTextureViews();
 
-                            // Only single-plane formats are supported right now, so assert only one
-                            // view exists.
-                            ASSERT(views[1].Get() == nullptr);
                             ASSERT(views[2].Get() == nullptr);
 
                             TextureView* textureView = ToBackend(views[0].Get());

src/dawn_native/opengl/CommandBufferGL.cpp

@@ -370,9 +370,6 @@ namespace dawn::native::opengl {
                                                    ->GetBindingAsExternalTexture(bindingIndex)
                                                    ->GetTextureViews();
 
-                            // Only single-plane formats are supported right now, so assert only one
-                            // view exists.
-                            ASSERT(textureViews[1].Get() == nullptr);
                             ASSERT(textureViews[2].Get() == nullptr);
 
                             TextureView* view = ToBackend(textureViews[0].Get());

src/dawn_native/vulkan/BindGroupVk.cpp

@@ -134,9 +134,6 @@ namespace dawn::native::vulkan {
                     const std::array<Ref<dawn::native::TextureViewBase>, kMaxPlanesPerFormat>&
                         textureViews = GetBindingAsExternalTexture(bindingIndex)->GetTextureViews();
 
-                    // Only single-plane formats are supported right now, so ensure only one view
-                    // exists.
-                    ASSERT(textureViews[1].Get() == nullptr);
                     ASSERT(textureViews[2].Get() == nullptr);
 
                     TextureView* view = ToBackend(textureViews[0].Get());