Enable stencil clipping in mixed sampled render targets

src/gpu/gl/GrGLGpu.cpp

Index: src/gpu/gl/GrGLGpu.cpp
diff --git a/src/gpu/gl/GrGLGpu.cpp b/src/gpu/gl/GrGLGpu.cpp
index c07f704d21342df6ebb7723c0358dca14351c903..d1bb3a9ea298ba722796da750508feb1e3f6f5fd 100644
--- a/src/gpu/gl/GrGLGpu.cpp
+++ b/src/gpu/gl/GrGLGpu.cpp
@@ -157,6 +157,29 @@ bool GrGLGpu::BlendCoeffReferencesConstant(GrBlendCoeff coeff) {
     GR_STATIC_ASSERT(kGrBlendCoeffCnt == SK_ARRAY_COUNT(gXfermodeCoeff2Blend));
 }
 
+// Sample locations that are colocated at pixel center.
+static const GrGLfloat gCenteredSampleLocations[2*16] = { 0.5f, 0.5f, 0.5f, 0.5f, 0.5f, 0.5f, 0.5f, 0.5f,
+                                                          0.5f, 0.5f, 0.5f, 0.5f, 0.5f, 0.5f, 0.5f, 0.5f,
+                                                          0.5f, 0.5f, 0.5f, 0.5f, 0.5f, 0.5f, 0.5f, 0.5f,
+                                                          0.5f, 0.5f, 0.5f, 0.5f, 0.5f, 0.5f, 0.5f, 0.5f };
+
+// Default sample pattern.
+static GrGLfloat defaultSampleLocations2x[]  = { 0.75f, 0.75f, 0.25f, 0.25f };
+static GrGLfloat defaultSampleLocations4x[]  = { 0.375f, 0.125f, 0.875f, 0.375f, 0.125f, 0.625f, 0.625f, 0.875f };
+static GrGLfloat defaultSampleLocations8x[]  = { 0.5625f, 0.3125f, 0.4375f, 0.6875f, 0.8125f, 0.5625f, 0.3125f, 0.1875f,
+                                                 0.1875f, 0.8125f, 0.0625f, 0.4375f, 0.6875f, 0.9375f, 0.9375f, 0.0625f };
+static GrGLfloat defaultSampleLocations16x[] = { 0.5625f, 0.5625f, 0.4375f, 0.3125f, 0.3125f, 0.625f, 0.75f, 0.4375f,
+                                                 0.1875f, 0.375f, 0.625f, 0.8125f, 0.8125f, 0.6875f, 0.6875f, 0.1875f,
+                                                 0.375f, 0.875f, 0.5f, 0.0625f, 0.25f, 0.125f, 0.125f, 0.75f,
+                                                 0.375f, 0.875f, 0.5f, 0.0625f, 0.25f, 0.125f, 0.125f, 0.75f,
+                                                 0.0f, 0.5f, 0.9375f, 0.25f, 0.875f, 0.9375f, 0.0625f, 0.0f };
+// Lookup table for sample locations array for sample count 0..16.
+static GrGLfloat* gDefaultSampleLocations[17] = { 0,
+                                                  0, defaultSampleLocations2x, 0, defaultSampleLocations4x,
+                                                  0, 0, 0, defaultSampleLocations8x,
+                                                  0, 0, 0, 0,
+                                                  0, 0, 0, defaultSampleLocations16x };
+
 ///////////////////////////////////////////////////////////////////////////////
 
 // Used in the map of pixel configs to stencil format indices. This value is used to
@@ -1477,7 +1500,7 @@ bool GrGLGpu::flushGLState(const DrawArgs& args) {
     GrGLRenderTarget* glRT = static_cast<GrGLRenderTarget*>(pipeline.getRenderTarget());
     this->flushStencil(pipeline.getStencil());
     this->flushScissor(pipeline.getScissorState(), glRT->getViewport(), glRT->origin());
-    this->flushHWAAState(glRT, pipeline.isHWAntialiasState());
+    this->flushHWAAState(glRT, pipeline.isHWAntialiasState(), !pipeline.getStencil().isDisabled());
 
     // This must come after textures are flushed because a texture may need
     // to be msaa-resolved (which will modify bound FBO state).
@@ -1900,6 +1923,33 @@ bool GrGLGpu::onReadPixels(GrSurface* surface,
     return true;
 }
 
+void GrGLGpu::setCenteredSampleLocations(GrRenderTarget* rt, bool useCenteredSampleLocations) {
+    GrGLRenderTarget* target = static_cast<GrGLRenderTarget*>(rt->asRenderTarget());
+    SkASSERT(0 != target->renderFBOID());
+
+    if (0 == rt->numRasterSamples() ||
+        useCenteredSampleLocations == rt->renderTargetPriv().usesCenteredSampleLocations()) {
+        return;
+    }
+
+    if (!rt->renderTargetPriv().programmableSampleLocationsEnabled()) {
+        GL_CALL(NamedFramebufferParameteri(target->renderFBOID(),
+                                           GR_GL_FRAMEBUFFER_PROGRAMMABLE_SAMPLE_LOCATIONS, true));
+        rt->renderTargetPriv().setProgrammableSampleLocationsEnabled(true);
+    }
+
+    SkASSERT(rt->numRasterSamples() == 2 ||
+             rt->numRasterSamples() == 4 ||
+             rt->numRasterSamples() == 8 ||
+             rt->numRasterSamples() == 16);
+
+    const GrGLfloat *sampleLocations =
+        useCenteredSampleLocations ? gCenteredSampleLocations
+                                   : gDefaultSampleLocations[rt->numRasterSamples()];
+    GL_CALL(NamedFramebufferSampleLocationsfv(target->renderFBOID(), 0, rt->numRasterSamples(), sampleLocations));
+    rt->renderTargetPriv().flagAsUsingCenteredSampleLocations(useCenteredSampleLocations);
+}
+
 void GrGLGpu::flushRenderTarget(GrGLRenderTarget* target, const SkIRect* bound) {
 
     SkASSERT(target);
@@ -2147,9 +2197,19 @@ void GrGLGpu::flushStencil(const GrStencilSettings& stencilSettings) {
     }
 }
 
-void GrGLGpu::flushHWAAState(GrRenderTarget* rt, bool useHWAA) {
+void GrGLGpu::flushHWAAState(GrRenderTarget* rt, bool useHWAA, bool stencilEnabled) {
     SkASSERT(!useHWAA || rt->isStencilBufferMultisampled());
 
+    if (rt->hasMixedSamples() && stencilEnabled &&
+        this->glCaps().glslCaps()->programmableSampleLocationsSupport()) {
+        if (useHWAA) {
+            setCenteredSampleLocations(rt, false);
+        } else {
+            setCenteredSampleLocations(rt, true);
+        }
+        useHWAA = true;
+    }
+
     if (this->glCaps().multisampleDisableSupport()) {
         if (useHWAA) {
             if (kYes_TriState != fMSAAEnabled) {
@@ -2932,7 +2992,7 @@ void GrGLGpu::copySurfaceAsDraw(GrSurface* dst,
     this->flushColorWrite(true);
     this->flushDither(false);
     this->flushDrawFace(GrPipelineBuilder::kBoth_DrawFace);
-    this->flushHWAAState(dstRT, false);
+    this->flushHWAAState(dstRT, false, false);
     this->disableScissor();
     GrStencilSettings stencil;
     stencil.setDisabled();