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, 4 insertions, 4 deletions

diff --git a/tests/SurfaceTest.cpp b/tests/SurfaceTest.cpp
index 471953b373..af73473fad 100644
--- a/tests/SurfaceTest.cpp
+++ b/tests/SurfaceTest.cpp
@@ -704,7 +704,7 @@ DEF_GPUTEST_FOR_GL_RENDERING_CONTEXTS(SurfaceClear_Gpu, reporter, ctxInfo) {
         for (auto& surfaceFunc : {&create_gpu_surface_backend_texture,
                                   &create_gpu_surface_backend_texture_as_render_target}) {
             GrBackendTexture backendTex;
-            auto surface = surfaceFunc(context, 0, kOrigColor, &backendTex);
+            auto surface = surfaceFunc(context, 1, kOrigColor, &backendTex);
             test_surface_clear(reporter, surface, grSurfaceGetter, kOrigColor);
             surface.reset();
             gpu->deleteTestingOnlyBackendTexture(&backendTex);
@@ -767,7 +767,7 @@ DEF_GPUTEST_FOR_RENDERING_CONTEXTS(SurfacePartialDraw_Gpu, reporter, ctxInfo) {
         // preserved in pixels that aren't rendered to via the surface.
         // This works only for non-multisampled case.
         GrBackendTexture backendTex;
-        auto surface = surfaceFunc(ctxInfo.grContext(), 0, kOrigColor, &backendTex);
+        auto surface = surfaceFunc(ctxInfo.grContext(), 1, kOrigColor, &backendTex);
         if (surface) {
             test_surface_draw_partially(reporter, surface, kOrigColor);
             surface.reset();
@@ -791,11 +791,11 @@ DEF_GPUTEST_FOR_GL_RENDERING_CONTEXTS(SurfaceAttachStencil_Gpu, reporter, ctxInf
 
     for (auto& surfaceFunc : {&create_gpu_surface_backend_texture,
                               &create_gpu_surface_backend_texture_as_render_target}) {
-        for (int sampleCnt : {0, 4, 8}) {
+        for (int sampleCnt : {1, 4, 8}) {
             GrBackendTexture backendTex;
             auto surface = surfaceFunc(ctxInfo.grContext(), sampleCnt, kOrigColor, &backendTex);
 
-            if (!surface && sampleCnt > 0) {
+            if (!surface && sampleCnt > 1) {
                 // Certain platforms don't support MSAA, skip these.
                 continue;
             }