Redefine the meaning of sample counts in GPU backend.

Old: 0  -> nonMSAA
     1+ -> MSAA

New:
     0  -> error/unsupported
     1  -> nonMSAA
     2+ -> MSAA

We still allow 0 to mean nonMSAA in three sets of public APIs for backwards compatibility:

1) SkSurface factories
2) GrBackendRenderTarget constructors
3) GrCaps::getSampleCnt()'s requestedCount parameter

However, we immediately clamp to 1 and treat 0 as invalid/non-renderable internally.

This also changes the behavior when using a large sample count. We now fail in that case rather than using the largest sample available sample count. GrCaps::getSampleCount() will return 0 in this case.


Bug: skia:
Change-Id: Ida22c6b22c1365e563c9046b611e88bf5eb3ff33
Reviewed-on: https://skia-review.googlesource.com/101560
Reviewed-by: Greg Daniel <egdaniel@google.com>
Commit-Queue: Brian Salomon <bsalomon@google.com>

1 files changed, 7 insertions, 3 deletions

diff --git a/src/gpu/GrProxyProvider.cpp b/src/gpu/GrProxyProvider.cpp
index ec05243d18..193b321190 100644
--- a/src/gpu/GrProxyProvider.cpp
+++ b/src/gpu/GrProxyProvider.cpp
@@ -322,12 +322,16 @@ sk_sp<GrTextureProxy> GrProxyProvider::createProxy(const GrSurfaceDesc& desc,
     }
 
     bool willBeRT = SkToBool(desc.fFlags & kRenderTarget_GrSurfaceFlag);
-    if (willBeRT && !caps->isConfigRenderable(desc.fConfig, desc.fSampleCnt > 0)) {
+    if (willBeRT && !caps->isConfigRenderable(desc.fConfig, desc.fSampleCnt > 1)) {
         return nullptr;
     }
 
     // We currently do not support multisampled textures
-    if (!willBeRT && desc.fSampleCnt > 0) {
+    if (!willBeRT && desc.fSampleCnt > 1) {
+        return nullptr;
+    }
+
+    if (willBeRT && !caps->getSampleCount(desc.fSampleCnt, desc.fConfig)) {
         return nullptr;
     }
 
@@ -505,7 +509,7 @@ sk_sp<GrTextureProxy> GrProxyProvider::createFullyLazyProxy(LazyInstantiateCallb
     desc.fWidth = -1;
     desc.fHeight = -1;
     desc.fConfig = config;
-    desc.fSampleCnt = 0;
+    desc.fSampleCnt = 1;
 
     return this->createLazyProxy(std::move(callback), desc, GrMipMapped::kNo,
                                  SkBackingFit::kApprox, SkBudgeted::kYes);