Fix caching of sample locations

The original caching logic for sample locations wishfully assumed that
the GPU would always use the same sample pattern for render targets
that had the same number of samples. It turns out we can't rely on
that. This change improves the caching logic to handle mismatched
simple patterns with the same count, and adds a unit test that
emulates different sample patterns observed on real hardware.

BUG=skia:
GOLD_TRYBOT_URL= https://gold.skia.org/search?issue=2111423002

Review-Url: https://codereview.chromium.org/2111423002

2 files changed, 7 insertions, 11 deletions

diff --git a/src/gpu/gl/GrGLGpu.cpp b/src/gpu/gl/GrGLGpu.cpp
index 2fb66804e0..9972690487 100644
--- a/src/gpu/gl/GrGLGpu.cpp
+++ b/src/gpu/gl/GrGLGpu.cpp
@@ -4432,10 +4432,8 @@ bool GrGLGpu::generateMipmap(GrGLTexture* texture, bool gammaCorrect) {
     return true;
 }
 
-void GrGLGpu::onGetMultisampleSpecs(GrRenderTarget* rt,
-                                    const GrStencilSettings& stencil,
-                                    int* effectiveSampleCnt,
-                                    SkAutoTDeleteArray<SkPoint>* sampleLocations) {
+void GrGLGpu::onGetMultisampleSpecs(GrRenderTarget* rt, const GrStencilSettings& stencil,
+                                    int* effectiveSampleCnt, SamplePattern* samplePattern) {
     SkASSERT(!rt->hasMixedSamples() || rt->renderTargetPriv().getStencilAttachment() ||
              stencil.isDisabled());
 
@@ -4452,14 +4450,14 @@ void GrGLGpu::onGetMultisampleSpecs(GrRenderTarget* rt,
     SkASSERT(*effectiveSampleCnt >= rt->desc().fSampleCnt);
 
     if (this->caps()->sampleLocationsSupport()) {
-        sampleLocations->reset(new SkPoint[*effectiveSampleCnt]);
+        samplePattern->reset(*effectiveSampleCnt);
         for (int i = 0; i < *effectiveSampleCnt; ++i) {
             GrGLfloat pos[2];
             GL_CALL(GetMultisamplefv(GR_GL_SAMPLE_POSITION, i, pos));
             if (kTopLeft_GrSurfaceOrigin == rt->origin()) {
-                (*sampleLocations)[i].set(pos[0], pos[1]);
+                (*samplePattern)[i].set(pos[0], pos[1]);
             } else {
-                (*sampleLocations)[i].set(pos[0], 1 - pos[1]);
+                (*samplePattern)[i].set(pos[0], 1 - pos[1]);
             }
         }
     }
diff --git a/src/gpu/gl/GrGLGpu.h b/src/gpu/gl/GrGLGpu.h
index b7daa431d8..5cc0facea6 100644
--- a/src/gpu/gl/GrGLGpu.h
+++ b/src/gpu/gl/GrGLGpu.h
@@ -220,10 +220,8 @@ private:
                        const SkIRect& srcRect,
                        const SkIPoint& dstPoint) override;
 
-    void onGetMultisampleSpecs(GrRenderTarget*,
-                               const GrStencilSettings&,
-                               int* effectiveSampleCnt,
-                               SkAutoTDeleteArray<SkPoint>* sampleLocations) override;
+    void onGetMultisampleSpecs(GrRenderTarget*, const GrStencilSettings&,
+                               int* effectiveSampleCnt, SamplePattern*) override;
 
     // binds texture unit in GL
     void setTextureUnit(int unitIdx);