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, 1 insertions, 1 deletions

diff --git a/example/HelloWorld.cpp b/example/HelloWorld.cpp
index 5954e71532..b20d30a780 100644
--- a/example/HelloWorld.cpp
+++ b/example/HelloWorld.cpp
@@ -38,7 +38,7 @@ HelloWorld::~HelloWorld() {
 }
 
 void HelloWorld::updateTitle() {
-    if (!fWindow || fWindow->sampleCount() < 0) {
+    if (!fWindow || fWindow->sampleCount() <= 1) {
         return;
     }