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, 2 insertions, 2 deletions

diff --git a/tests/BlendTest.cpp b/tests/BlendTest.cpp
index b17b9f1e45..3ac7e3c41c 100644
--- a/tests/BlendTest.cpp
+++ b/tests/BlendTest.cpp
@@ -140,7 +140,7 @@ DEF_GPUTEST_FOR_GL_RENDERING_CONTEXTS(ES2BlendWithNoTexture, reporter, ctxInfo)
     std::vector<TestCase> testCases;
 
     for (auto origin : { kTopLeft_GrSurfaceOrigin, kBottomLeft_GrSurfaceOrigin}) {
-        for (int sampleCnt : {0, 4}) {
+        for (int sampleCnt : {1, 4}) {
             for (auto rectAndPoints : allRectsAndPoints) {
                 for (auto clip : {SkRect::MakeXYWH(0, 0, 10, 10), SkRect::MakeXYWH(1, 1, 8, 8)}) {
                     testCases.push_back({rectAndPoints, clip, sampleCnt, origin});
@@ -162,7 +162,7 @@ DEF_GPUTEST_FOR_GL_RENDERING_CONTEXTS(ES2BlendWithNoTexture, reporter, ctxInfo)
         sk_sp<SkSurface> surface = create_gpu_surface_backend_texture_as_render_target(
                 context, sampleCnt, kWidth, kHeight, kColorType, kConfig, origin, &backingSurface);
 
-        if (!surface && sampleCnt > 0) {
+        if (!surface && sampleCnt > 1) {
             // Some platforms don't support MSAA.
             continue;
         }