Vulkan: Fix deferred clears vs swap

src/libANGLE/renderer/vulkan/SurfaceVk.cpp

@@ -1283,6 +1283,10 @@ angle::Result WindowSurfaceVk::present(ContextVk *contextVk,
     updateOverlay(contextVk);
     bool overlayHasWidget = overlayHasEnabledWidget(contextVk);
 
+    // Make sure deferred clears are applied, if any.
+    ANGLE_TRY(
+        image.image.flushStagedUpdates(contextVk, gl::LevelIndex(0), gl::LevelIndex(1), 0, 1, {}));
+
     // We can only do present related optimization if this is the last renderpass that touches the
     // swapchain image. MSAA resolve and overlay will insert another renderpass which disqualifies
     // the optimization.

src/tests/gl_tests/ClearTest.cpp

@@ -10,6 +10,7 @@
 #include "test_utils/gl_raii.h"
 #include "util/random_utils.h"
 #include "util/shader_utils.h"
+#include "util/test_utils.h"
 
 using namespace angle;
 
@@ -2425,6 +2426,27 @@ TEST_P(ClearTest, ClearThenScissoredMaskedClear)
     EXPECT_PIXEL_RECT_EQ(kSize / 2, 0, kSize / 2, kSize, GLColor::red);
 }
 
+// This is a test that must be verified visually.
+//
+// Tests that clear of the default framebuffer applies to the window.
+TEST_P(ClearTest, DISABLED_ClearReachesWindow)
+{
+    ANGLE_GL_PROGRAM(blueProgram, essl1_shaders::vs::Simple(), essl1_shaders::fs::Blue());
+
+    // Draw blue.
+    drawQuad(blueProgram, essl1_shaders::PositionAttrib(), 0.5f);
+    swapBuffers();
+
+    // Use glClear to clear to red.  Regression test for the Vulkan backend where this clear
+    // remained "deferred" and didn't make it to the window on swap.
+    glClearColor(1.0f, 0.0f, 0.0f, 1.0f);
+    glClear(GL_COLOR_BUFFER_BIT);
+    swapBuffers();
+
+    // Wait for visual verification.
+    angle::Sleep(2000);
+}
+
 #ifdef Bool
 // X11 craziness.
 #    undef Bool