Vulkan: Add support for FBO with unequal sized attachments

OpenGLES 3.0 allows FBO with unequal sized attachments. This CL removes
assertion that all attachment must have equal size from vulkan backend,
and uses common intersect area to create VkFramebuffer object.

Bug: b/181800403
Change-Id: Icbb12a26784b184ebd91740855672013f64b889d
Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/2824760
Commit-Queue: Charlie Lao <cclao@google.com>
Reviewed-by: Jamie Madill <jmadill@chromium.org>
Reviewed-by: Tim Van Patten <timvp@google.com>

src/libANGLE/Framebuffer.cpp

@@ -517,6 +517,34 @@ const FramebufferAttachment *FramebufferState::getDepthStencilAttachment() const
     return nullptr;
 }
 
+const Extents FramebufferState::getAttachmentExtentsIntersection() const
+{
+    int32_t width  = std::numeric_limits<int32_t>::max();
+    int32_t height = std::numeric_limits<int32_t>::max();
+    for (const FramebufferAttachment &attachment : mColorAttachments)
+    {
+        if (attachment.isAttached())
+        {
+            width  = std::min(width, attachment.getSize().width);
+            height = std::min(height, attachment.getSize().height);
+        }
+    }
+
+    if (mDepthAttachment.isAttached())
+    {
+        width  = std::min(width, mDepthAttachment.getSize().width);
+        height = std::min(height, mDepthAttachment.getSize().height);
+    }
+
+    if (mStencilAttachment.isAttached())
+    {
+        width  = std::min(width, mStencilAttachment.getSize().width);
+        height = std::min(height, mStencilAttachment.getSize().height);
+    }
+
+    return Extents(width, height, 0);
+}
+
 bool FramebufferState::attachmentsHaveSameDimensions() const
 {
     Optional<Extents> attachmentSize;
@@ -673,11 +701,12 @@ Box FramebufferState::getDimensions() const
 
 Extents FramebufferState::getExtents() const
 {
-    ASSERT(attachmentsHaveSameDimensions());
+    // OpenGLES3.0 (https://www.khronos.org/registry/OpenGL/specs/es/3.0/es_spec_3.0.pdf
+    // section 4.4.4.2) allows attachments have unequal size.
     const FramebufferAttachment *first = getFirstNonNullAttachment();
     if (first)
     {
-        return first->getSize();
+        return getAttachmentExtentsIntersection();
     }
     return Extents(getDefaultWidth(), getDefaultHeight(), 0);
 }

src/libANGLE/Framebuffer.h

@@ -81,6 +81,7 @@ class FramebufferState final : angle::NonCopyable
     }
     const DrawBufferMask getColorAttachmentsMask() const { return mColorAttachmentsMask; }
 
+    const Extents getAttachmentExtentsIntersection() const;
     bool attachmentsHaveSameDimensions() const;
     bool hasSeparateDepthAndStencilAttachments() const;
     bool colorAttachmentsAreUniqueImages() const;

src/libANGLE/renderer/vulkan/FramebufferVk.cpp

@@ -2020,7 +2020,8 @@ angle::Result FramebufferVk::getFramebuffer(ContextVk *contextVk,
 
     // Gather VkImageViews over all FBO attachments, also size of attached region.
     std::vector<VkImageView> attachments;
-    gl::Extents attachmentsSize;
+    gl::Extents attachmentsSize = mState.getExtents();
+    ASSERT(attachmentsSize.width != 0 && attachmentsSize.height != 0);
 
     // Color attachments.
     const auto &colorRenderTargets = mRenderTargetCache.getColors();
@@ -2034,9 +2035,6 @@ angle::Result FramebufferVk::getFramebuffer(ContextVk *contextVk,
             contextVk, mCurrentFramebufferDesc.getWriteControlMode(), &imageView));
 
         attachments.push_back(imageView->getHandle());
-
-        ASSERT(attachmentsSize.empty() || attachmentsSize == colorRenderTarget->getExtents());
-        attachmentsSize = colorRenderTarget->getExtents();
     }
 
     // Depth/stencil attachment.
@@ -2047,10 +2045,6 @@ angle::Result FramebufferVk::getFramebuffer(ContextVk *contextVk,
         ANGLE_TRY(depthStencilRenderTarget->getImageView(contextVk, &imageView));
 
         attachments.push_back(imageView->getHandle());
-
-        ASSERT(attachmentsSize.empty() ||
-               attachmentsSize == depthStencilRenderTarget->getExtents());
-        attachmentsSize = depthStencilRenderTarget->getExtents();
     }
 
     // Color resolve attachments.
@@ -2076,8 +2070,6 @@ angle::Result FramebufferVk::getFramebuffer(ContextVk *contextVk,
                 ANGLE_TRY(colorRenderTarget->getResolveImageView(contextVk, &resolveImageView));
 
                 attachments.push_back(resolveImageView->getHandle());
-
-                ASSERT(!attachmentsSize.empty());
             }
         }
     }
@@ -2089,17 +2081,8 @@ angle::Result FramebufferVk::getFramebuffer(ContextVk *contextVk,
         ANGLE_TRY(depthStencilRenderTarget->getResolveImageView(contextVk, &imageView));
 
         attachments.push_back(imageView->getHandle());
-
-        ASSERT(!attachmentsSize.empty());
     }
 
-    if (attachmentsSize.empty())
-    {
-        // No attachments, so use the default values.
-        attachmentsSize.height = mState.getDefaultHeight();
-        attachmentsSize.width  = mState.getDefaultWidth();
-        attachmentsSize.depth  = 0;
-    }
     VkFramebufferCreateInfo framebufferInfo = {};
 
     framebufferInfo.sType           = VK_STRUCTURE_TYPE_FRAMEBUFFER_CREATE_INFO;
@@ -2708,10 +2691,6 @@ angle::Result FramebufferVk::readPixelsImpl(ContextVk *contextVk,
 gl::Extents FramebufferVk::getReadImageExtents() const
 {
     RenderTargetVk *readRenderTarget = mRenderTargetCache.getColorRead(mState);
-
-    ASSERT(readRenderTarget->getExtents().width == mState.getDimensions().width);
-    ASSERT(readRenderTarget->getExtents().height == mState.getDimensions().height);
-
     return readRenderTarget->getExtents();
 }
 

src/tests/gl_tests/FramebufferTest.cpp

@@ -3054,8 +3054,6 @@ TEST_P(FramebufferTest_ES3, ChangeAttachmentThenInvalidateAndDraw)
 // outside common intersection area are undefined.
 TEST_P(FramebufferTest_ES3, AttachmentsWithUnequalDimensions)
 {
-    // TODO: https://issuetracker.google.com/181800403
-    ANGLE_SKIP_TEST_IF(IsVulkan());
     // TODO: https://anglebug.com/5866
     ANGLE_SKIP_TEST_IF(IsD3D() || IsMetal());