Vulkan: Avoid recopying the data every time we draw line loops

src/libANGLE/Observer.cpp

@@ -115,4 +115,9 @@ void ObserverBinding::onSubjectReset()
 {
     mSubject = nullptr;
 }
+
+const Subject *ObserverBinding::getSubject() const
+{
+    return mSubject;
+}
 }  // namespace angle

src/libANGLE/Observer.h

@@ -77,6 +77,8 @@ class ObserverBinding final
     void onStateChange(const gl::Context *context, SubjectMessage message) const;
     void onSubjectReset();
 
+    const Subject *getSubject() const;
+
   private:
     Subject *mSubject;
     ObserverInterface *mObserver;

src/libANGLE/renderer/vulkan/BufferVk.cpp

@@ -84,6 +84,7 @@ gl::Error BufferVk::setData(const gl::Context *context,
         ANGLE_TRY(setDataImpl(contextVk, static_cast<const uint8_t *>(data), size, 0));
     }
 
+    onStateChange(context, angle::SubjectMessage::STATE_CHANGE);
     return gl::NoError();
 }
 
@@ -99,6 +100,7 @@ gl::Error BufferVk::setSubData(const gl::Context *context,
     ContextVk *contextVk = vk::GetImpl(context);
     ANGLE_TRY(setDataImpl(contextVk, static_cast<const uint8_t *>(data), size, offset));
 
+    onStateChange(context, angle::SubjectMessage::STATE_CHANGE);
     return gl::NoError();
 }
 
@@ -122,6 +124,7 @@ gl::Error BufferVk::map(const gl::Context *context, GLenum access, void **mapPtr
     ANGLE_TRY(
         mBufferMemory.map(device, 0, mState.getSize(), 0, reinterpret_cast<uint8_t **>(mapPtr)));
 
+    onStateChange(context, angle::SubjectMessage::STATE_CHANGE);
     return gl::NoError();
 }
 
@@ -138,6 +141,7 @@ gl::Error BufferVk::mapRange(const gl::Context *context,
 
     ANGLE_TRY(mBufferMemory.map(device, offset, length, 0, reinterpret_cast<uint8_t **>(mapPtr)));
 
+    onStateChange(context, angle::SubjectMessage::STATE_CHANGE);
     return gl::NoError();
 }
 
@@ -150,6 +154,7 @@ gl::Error BufferVk::unmap(const gl::Context *context, GLboolean *result)
 
     mBufferMemory.unmap(device);
 
+    onStateChange(context, angle::SubjectMessage::STATE_CHANGE);
     return gl::NoError();
 }
 

src/libANGLE/renderer/vulkan/BufferVk.h

@@ -10,6 +10,7 @@
 #ifndef LIBANGLE_RENDERER_VULKAN_BUFFERVK_H_
 #define LIBANGLE_RENDERER_VULKAN_BUFFERVK_H_
 
+#include "libANGLE/Observer.h"
 #include "libANGLE/renderer/BufferImpl.h"
 #include "libANGLE/renderer/vulkan/vk_utils.h"
 
@@ -17,7 +18,7 @@ namespace rx
 {
 class RendererVk;
 
-class BufferVk : public BufferImpl, public ResourceVk
+class BufferVk : public BufferImpl, public ResourceVk, public angle::Subject
 {
   public:
     BufferVk(const gl::BufferState &state);

src/libANGLE/renderer/vulkan/vk_utils.cpp

@@ -1330,7 +1330,8 @@ void GarbageObject::destroy(VkDevice device)
 }
 
 LineLoopHandler::LineLoopHandler()
-    : mStreamingLineLoopIndicesData(
+    : mObserverBinding(this, 0u),
+      mStreamingLineLoopIndicesData(
           new StreamingBuffer(VK_BUFFER_USAGE_INDEX_BUFFER_BIT | VK_BUFFER_USAGE_TRANSFER_DST_BIT,
                               kLineLoopStreamingBufferMinSize)),
       mLineLoopIndexBuffer(VK_NULL_HANDLE),
@@ -1385,16 +1386,17 @@ gl::Error LineLoopHandler::createIndexBufferFromElementArrayBuffer(ContextVk *co
 {
     ASSERT(indexType == VK_INDEX_TYPE_UINT16 || indexType == VK_INDEX_TYPE_UINT32);
 
-    if (mLineLoopIndexBuffer != VK_NULL_HANDLE)
+    if (bufferVk == mObserverBinding.getSubject() && mLineLoopIndexBuffer != VK_NULL_HANDLE)
     {
         return gl::NoError();
     }
 
+    // We want to know if the bufferVk changes at any point in time, because if it does we need to
+    // recopy our data on the next call.
+    mObserverBinding.bind(bufferVk);
+
     uint32_t *indices = nullptr;
 
-    // TODO: Use the signal_utils to know when the user's bufferVk has changed and if it did we copy
-    // again. Otherwise if we already created that fake index buffer we keep it and avoid recopying
-    // every time.
     auto unitSize = (indexType == VK_INDEX_TYPE_UINT16 ? sizeof(uint16_t) : sizeof(uint32_t));
     ANGLE_TRY(mStreamingLineLoopIndicesData->allocate(
         contextVk, unitSize * (count + 1), reinterpret_cast<uint8_t **>(&indices),
@@ -1416,12 +1418,12 @@ gl::Error LineLoopHandler::createIndexBufferFromElementArrayBuffer(ContextVk *co
                               copies.data());
 
     ANGLE_TRY(mStreamingLineLoopIndicesData->flush(contextVk));
-
     return gl::NoError();
 }
 
 void LineLoopHandler::destroy(VkDevice device)
 {
+    mObserverBinding.reset();
     mStreamingLineLoopIndicesData->destroy(device);
 }
 
@@ -1438,6 +1440,17 @@ ResourceVk *LineLoopHandler::getLineLoopBufferResource()
 {
     return mStreamingLineLoopIndicesData.get();
 }
+
+void LineLoopHandler::onSubjectStateChange(const gl::Context *context,
+                                           angle::SubjectIndex index,
+                                           angle::SubjectMessage message)
+{
+    // Indicate we want to recopy on next draw since something changed in the buffer.
+    if (message == angle::SubjectMessage::STATE_CHANGE)
+    {
+        mLineLoopIndexBuffer = VK_NULL_HANDLE;
+    }
+}
 }  // namespace vk
 
 namespace gl_vk

src/libANGLE/renderer/vulkan/vk_utils.h

@@ -17,6 +17,7 @@
 #include "common/Optional.h"
 #include "common/debug.h"
 #include "libANGLE/Error.h"
+#include "libANGLE/Observer.h"
 #include "libANGLE/renderer/renderer_utils.h"
 
 #define ANGLE_GL_OBJECTS_X(PROC) \
@@ -680,7 +681,7 @@ Error AllocateImageMemory(RendererVk *renderer,
 // first/last vertex and the current commandBuffer. If the user wants to draw a loop between [v1,
 // v2, v3], we will create an indexed buffer with these indexes: [0, 1, 2, 3, 0] to emulate the
 // loop.
-class LineLoopHandler final : angle::NonCopyable
+class LineLoopHandler final : angle::NonCopyable, angle::ObserverInterface
 {
   public:
     LineLoopHandler();
@@ -699,7 +700,13 @@ class LineLoopHandler final : angle::NonCopyable
 
     ResourceVk *getLineLoopBufferResource();
 
+    // Observer interface implementation.
+    void onSubjectStateChange(const gl::Context *context,
+                              angle::SubjectIndex index,
+                              angle::SubjectMessage message) override;
+
   private:
+    angle::ObserverBinding mObserverBinding;
     std::unique_ptr<StreamingBuffer> mStreamingLineLoopIndicesData;
     VkBuffer mLineLoopIndexBuffer;
     VkDeviceSize mLineLoopIndexBufferOffset;