Vulkan: Implement scissor test and add a simple test for it

src/libANGLE/renderer/vulkan/ContextVk.cpp

@@ -416,14 +416,34 @@ void ContextVk::syncState(const gl::Context *context, const gl::State::DirtyBits
         switch (dirtyBit)
         {
             case gl::State::DIRTY_BIT_SCISSOR_TEST_ENABLED:
-                WARN() << "DIRTY_BIT_SCISSOR_TEST_ENABLED unimplemented";
+                if (glState.isScissorTestEnabled())
+                {
+                    mPipelineDesc->updateScissor(glState.getScissor());
+                }
+                else
+                {
+                    mPipelineDesc->updateScissor(glState.getViewport());
+                }
                 break;
             case gl::State::DIRTY_BIT_SCISSOR:
-                WARN() << "DIRTY_BIT_SCISSOR unimplemented";
+                // Only modify the scissor region if the test is enabled, otherwise we want to keep
+                // the viewport size as the scissor region.
+                if (glState.isScissorTestEnabled())
+                {
+                    mPipelineDesc->updateScissor(glState.getScissor());
+                }
                 break;
             case gl::State::DIRTY_BIT_VIEWPORT:
                 mPipelineDesc->updateViewport(glState.getViewport(), glState.getNearPlane(),
                                               glState.getFarPlane());
+
+                // If the scissor test isn't enabled, we have to also update the scissor to
+                // be equal to the viewport to make sure we keep rendering everything in the
+                // viewport.
+                if (!glState.isScissorTestEnabled())
+                {
+                    mPipelineDesc->updateScissor(glState.getViewport());
+                }
                 break;
             case gl::State::DIRTY_BIT_DEPTH_RANGE:
                 WARN() << "DIRTY_BIT_DEPTH_RANGE unimplemented";

src/libANGLE/renderer/vulkan/vk_cache_utils.cpp

@@ -607,6 +607,12 @@ void PipelineDesc::updateRenderPassDesc(const RenderPassDesc &renderPassDesc)
     mRenderPassDesc = renderPassDesc;
 }
 
+void PipelineDesc::updateScissor(const gl::Rectangle &rect)
+{
+    mScissor = {{rect.x, rect.y},
+                {static_cast<uint32_t>(rect.width), static_cast<uint32_t>(rect.height)}};
+}
+
 // AttachmentOpsArray implementation.
 AttachmentOpsArray::AttachmentOpsArray()
 {

src/libANGLE/renderer/vulkan/vk_cache_utils.h

@@ -287,6 +287,9 @@ class PipelineDesc final
     const RenderPassDesc &getRenderPassDesc() const;
     void updateRenderPassDesc(const RenderPassDesc &renderPassDesc);
 
+    // Scissor support
+    void updateScissor(const gl::Rectangle &rect);
+
   private:
     // TODO(jmadill): Handle Geometry/Compute shaders when necessary.
     ShaderStageInfo mShaderStageInfo;

src/tests/gl_tests/SimpleOperationTest.cpp

@@ -104,6 +104,28 @@ TEST_P(SimpleOperationTest, ClearAndSwap)
     EXPECT_EGL_SUCCESS();
 }
 
+// Simple case of setting a scissor, enabled or disabled.
+TEST_P(SimpleOperationTest, ScissorTest)
+{
+    ANGLE_GL_PROGRAM(program, kBasicVertexShader, kGreenFragmentShader);
+
+    glClear(GL_COLOR_BUFFER_BIT);
+    glEnable(GL_SCISSOR_TEST);
+    glScissor(getWindowWidth() / 4, getWindowHeight() / 4, getWindowWidth() / 2,
+              getWindowHeight() / 2);
+
+    // Fill the whole screen with a quad.
+    drawQuad(program.get(), "position", 0.0f, 1.0f, true);
+
+    ASSERT_GL_NO_ERROR();
+
+    // Test outside the scissor test, pitch black.
+    EXPECT_PIXEL_COLOR_EQ(0, 0, GLColor::transparentBlack);
+
+    // Test inside, green of the fragment shader.
+    EXPECT_PIXEL_COLOR_EQ(getWindowWidth() / 2, getWindowHeight() / 2, GLColor::green);
+}
+
 TEST_P(SimpleOperationTest, LinkProgramShadersNoInputs)
 {
     const std::string vsSource =

src/tests/gl_tests/StateChangeTest.cpp

@@ -1067,6 +1067,64 @@ TEST_P(SimpleStateChangeTest, RedefineFramebufferInUse)
     ASSERT_GL_NO_ERROR();
 }
 
+TEST_P(SimpleStateChangeTest, ScissorTest)
+{
+    // This test validates this order of state changes:
+    // 1- Set scissor but don't enable it, validate its not used.
+    // 2- Enable it and validate its working.
+    // 3- Disable the scissor validate its not used anymore.
+
+    ANGLE_GL_PROGRAM(program, kSolidColorVertexShader, kSolidColorFragmentShader);
+
+    glClear(GL_COLOR_BUFFER_BIT);
+
+    // Set the scissor region, but don't enable it yet.
+    glScissor(getWindowWidth() / 4, getWindowHeight() / 4, getWindowWidth() / 2,
+              getWindowHeight() / 2);
+
+    // Fill the whole screen with a quad.
+    drawQuad(program.get(), "position", 0.0f, 1.0f, true);
+
+    ASSERT_GL_NO_ERROR();
+
+    // Test outside, scissor isnt enabled so its red.
+    EXPECT_PIXEL_COLOR_EQ(0, 0, GLColor::red);
+
+    // Test inside, red of the fragment shader.
+    EXPECT_PIXEL_COLOR_EQ(getWindowWidth() / 2, getWindowHeight() / 2, GLColor::red);
+
+    // Clear everything and start over with the test enabled.
+    glClear(GL_COLOR_BUFFER_BIT);
+    glEnable(GL_SCISSOR_TEST);
+
+    drawQuad(program.get(), "position", 0.0f, 1.0f, true);
+
+    ASSERT_GL_NO_ERROR();
+
+    // Test outside the scissor test, pitch black.
+    EXPECT_PIXEL_COLOR_EQ(0, 0, GLColor::transparentBlack);
+
+    // Test inside, red of the fragment shader.
+    EXPECT_PIXEL_COLOR_EQ(getWindowWidth() / 2, getWindowHeight() / 2, GLColor::red);
+
+    // Now disable the scissor test, do it again, and verify the region isn't used
+    // for the scissor test.
+    glDisable(GL_SCISSOR_TEST);
+
+    // Clear everything and start over with the test enabled.
+    glClear(GL_COLOR_BUFFER_BIT);
+
+    drawQuad(program.get(), "position", 0.0f, 1.0f, true);
+
+    ASSERT_GL_NO_ERROR();
+
+    // Test outside, scissor isnt enabled so its red.
+    EXPECT_PIXEL_COLOR_EQ(0, 0, GLColor::red);
+
+    // Test inside, red of the fragment shader.
+    EXPECT_PIXEL_COLOR_EQ(getWindowWidth() / 2, getWindowHeight() / 2, GLColor::red);
+}
+
 }  // anonymous namespace
 
 ANGLE_INSTANTIATE_TEST(StateChangeTest, ES2_D3D9(), ES2_D3D11(), ES2_OPENGL());