Store current pack operation as a queued command.

src/libGLESv2/renderer/d3d11/BufferStorage11.cpp

@@ -142,11 +142,14 @@ class BufferStorage11::PackStorage11 : public BufferStorage11::TypedBufferStorag
     void packPixels(ID3D11Texture2D *srcTexure, UINT srcSubresource, const PackPixelsParams &params);
 
   private:
+
+    void flushQueuedPackCommand();
+
     ID3D11Texture2D *mStagingTexture;
     DXGI_FORMAT mTextureFormat;
     gl::Extents mTextureSize;
     unsigned char *mMemoryBuffer;
-    PackPixelsParams mPackParams;
+    PackPixelsParams *mQueuedPackCommand;
     bool mDataModified;
 };
 
@@ -634,6 +637,7 @@ BufferStorage11::PackStorage11::PackStorage11(Renderer11 *renderer)
       mStagingTexture(NULL),
       mTextureFormat(DXGI_FORMAT_UNKNOWN),
       mMemoryBuffer(NULL),
+      mQueuedPackCommand(NULL),
       mDataModified(false)
 {
 }
@@ -642,6 +646,7 @@ BufferStorage11::PackStorage11::~PackStorage11()
 {
     SafeRelease(mStagingTexture);
     SafeDeleteArray(mMemoryBuffer);
+    SafeDelete(mQueuedPackCommand);
 }
 
 bool BufferStorage11::PackStorage11::copyFromStorage(TypedBufferStorage11 *source, size_t sourceOffset,
@@ -677,10 +682,8 @@ void *BufferStorage11::PackStorage11::map(GLbitfield access)
     //  and if D3D packs the staging texture memory identically to how we would fill
     //  the pack buffer according to the current pack state.
 
-    ASSERT(mMemoryBuffer);
-    mRenderer->packPixels(mStagingTexture, mPackParams, mMemoryBuffer);
+    flushQueuedPackCommand();
     mDataModified = (mDataModified || (access & GL_MAP_WRITE_BIT) != 0);
-
     return mMemoryBuffer;
 }
 
@@ -691,7 +694,8 @@ void BufferStorage11::PackStorage11::unmap()
 
 void BufferStorage11::PackStorage11::packPixels(ID3D11Texture2D *srcTexure, UINT srcSubresource, const PackPixelsParams &params)
 {
-    mPackParams = params;
+    flushQueuedPackCommand();
+    mQueuedPackCommand = new PackPixelsParams(params);
 
     D3D11_TEXTURE2D_DESC textureDesc;
     srcTexure->GetDesc(&textureDesc);
@@ -752,4 +756,15 @@ void BufferStorage11::PackStorage11::packPixels(ID3D11Texture2D *srcTexure, UINT
     immediateContext->CopySubresourceRegion(mStagingTexture, 0, 0, 0, 0, srcTexure, srcSubresource, &srcBox);
 }
 
+void BufferStorage11::PackStorage11::flushQueuedPackCommand()
+{
+    ASSERT(mMemoryBuffer);
+
+    if (mQueuedPackCommand)
+    {
+        mRenderer->packPixels(mStagingTexture, *mQueuedPackCommand, mMemoryBuffer);
+        SafeDelete(mQueuedPackCommand);
+    }
+}
+
 }

tests/angle_tests/ReadPixelsTest.cpp

@@ -141,3 +141,41 @@ TEST_F(ReadPixelsTest, pbo_with_other_target)
     glUnmapBuffer(GL_ARRAY_BUFFER);
     EXPECT_GL_NO_ERROR();
 }
+
+TEST_F(ReadPixelsTest, pbo_with_existing_data)
+{
+    // Clear backbuffer to red
+    glClearColor(1.0f, 0.0f, 0.0f, 1.0f);
+    glClear(GL_COLOR_BUFFER_BIT);
+    EXPECT_GL_NO_ERROR();
+
+    // Read 16x16 region from red backbuffer to PBO
+    glBindBuffer(GL_PIXEL_PACK_BUFFER, mPBO);
+    glReadPixels(0, 0, 16, 16, GL_RGBA, GL_UNSIGNED_BYTE, 0);
+
+    // Clear backbuffer to green
+    glClearColor(0.0f, 1.0f, 0.0f, 1.0f);
+    glClear(GL_COLOR_BUFFER_BIT);
+    EXPECT_GL_NO_ERROR();
+
+    // Read 16x16 region from green backbuffer to PBO at offset 16
+    glReadPixels(0, 0, 16, 16, GL_RGBA, GL_UNSIGNED_BYTE, reinterpret_cast<GLvoid*>(16));
+    GLvoid * mappedPtr = glMapBufferRange(GL_PIXEL_PACK_BUFFER, 0, 32, GL_MAP_READ_BIT);
+    unsigned char *dataPtr = static_cast<unsigned char *>(mappedPtr);
+    EXPECT_GL_NO_ERROR();
+
+    // Test pixel 0 is red (existing data)
+    EXPECT_EQ(255, dataPtr[0]);
+    EXPECT_EQ(0, dataPtr[1]);
+    EXPECT_EQ(0, dataPtr[2]);
+    EXPECT_EQ(255, dataPtr[3]);
+
+    // Test pixel 16 is green (new data)
+    EXPECT_EQ(0, dataPtr[16 * 4 + 0]);
+    EXPECT_EQ(255, dataPtr[16 * 4 + 1]);
+    EXPECT_EQ(0, dataPtr[16 * 4 + 2]);
+    EXPECT_EQ(255, dataPtr[16 * 4 + 3]);
+
+    glUnmapBuffer(GL_PIXEL_PACK_BUFFER);
+    EXPECT_GL_NO_ERROR();
+}