Add test for scissored clear.

src/tests/gl_tests/ClearTest.cpp

@@ -426,6 +426,53 @@ TEST_P(ClearTestES3, RepeatedClear)
     ASSERT_GL_NO_ERROR();
 }
 
+class ScissoredClearTest : public ANGLETest
+{
+  public:
+    ScissoredClearTest()
+    {
+        setWindowWidth(64);
+        setWindowHeight(64);
+        setConfigRedBits(8);
+        setConfigGreenBits(8);
+        setConfigBlueBits(8);
+        setConfigAlphaBits(8);
+    }
+};
+
+// Simple scissored clear.
+TEST_P(ScissoredClearTest, BasicScissoredColorClear)
+{
+    // The Vulkan back-end does not implement scissored clears yet.
+    // TODO(jmadill): Enable this when we implement scissored clears in Vulkan.
+    // http://anglebug.com/2356
+    ANGLE_SKIP_TEST_IF(IsVulkan());
+
+    const int w     = getWindowWidth();
+    const int h     = getWindowHeight();
+    const int whalf = w >> 1;
+    const int hhalf = h >> 1;
+
+    // Clear who region to red.
+    glClearColor(1.0, 0.0, 0.0, 1.0);
+    glClear(GL_COLOR_BUFFER_BIT);
+
+    // Enable scissor and clear to green.
+    glEnable(GL_SCISSOR_TEST);
+    glScissor(whalf / 2, hhalf / 2, whalf, whalf);
+    glClearColor(0.0, 1.0, 0.0, 1.0);
+    glClear(GL_COLOR_BUFFER_BIT);
+    ASSERT_GL_NO_ERROR();
+
+    // Check the four corners for the original clear color, and the middle for the scissored clear
+    // color.
+    EXPECT_PIXEL_COLOR_EQ(0, 0, GLColor::red) << "out-of-scissor area should be red";
+    EXPECT_PIXEL_COLOR_EQ(w - 1, 0, GLColor::red) << "out-of-scissor area should be red";
+    EXPECT_PIXEL_COLOR_EQ(0, h - 1, GLColor::red) << "out-of-scissor area should be red";
+    EXPECT_PIXEL_COLOR_EQ(w - 1, h - 1, GLColor::red) << "out-of-scissor area should be red";
+    EXPECT_PIXEL_COLOR_EQ(whalf, hhalf, GLColor::green) << "in-scissor area should be green";
+}
+
 // Use this to select which configurations (e.g. which renderer, which GLES major version) these tests should be run against.
 ANGLE_INSTANTIATE_TEST(ClearTest,
                        ES2_D3D9(),
@@ -436,5 +483,6 @@ ANGLE_INSTANTIATE_TEST(ClearTest,
                        ES2_OPENGLES(),
                        ES3_OPENGLES());
 ANGLE_INSTANTIATE_TEST(ClearTestES3, ES3_D3D11(), ES3_OPENGL(), ES3_OPENGLES());
+ANGLE_INSTANTIATE_TEST(ScissoredClearTest, ES2_D3D11(), ES2_OPENGL(), ES2_VULKAN());
 
 }  // anonymous namespace