Revert "Revert "Redefine the meaning of sample counts in GPU backend.""

Fixes gpu config default samples to be 1 and updates config parsing test accordingly.

This reverts commit c1ce2f7966babaae0deb150f93f1227ee5af9285.

Bug: skia:
Change-Id: I456973b1f52ced85a2011ea10fc49449bfc5846f
Reviewed-on: https://skia-review.googlesource.com/102147
Reviewed-by: Brian Salomon <bsalomon@google.com>
Commit-Queue: Brian Salomon <bsalomon@google.com>

2 files changed, 11 insertions, 4 deletions

diff --git a/src/utils/win/SkWGL.h b/src/utils/win/SkWGL.h
index c6c9479abe..cd19f2eeba 100644
--- a/src/utils/win/SkWGL.h
+++ b/src/utils/win/SkWGL.h
@@ -83,7 +83,8 @@ public:
      * priority are:
      *     * Choose formats with the smallest sample count that is >=
      *       desiredSampleCount (or the largest sample count if all formats have
-     *       fewer samples than desiredSampleCount.)
+     *       fewer samples than desiredSampleCount.) If desiredSampleCount is 1 then
+     *       all msaa formats are excluded from consideration.
      *     * Choose formats with the fewest color samples when coverage sampling
      *       is available.
      *     * If the above rules leave multiple formats, choose the one that
@@ -130,8 +131,9 @@ enum SkWGLContextRequest {
 /**
  * Helper to create an OpenGL context for a DC using WGL. Configs with a sample count >= to
  * msaaSampleCount are preferred but if none is available then a context with a lower sample count
- * (including non-MSAA) will be created. If preferCoreProfile is true but a core profile cannot be
- * created then a compatible profile context will be created.
+ * (including non-MSAA) will be created. If msaaSampleCount is 1 then this will fail if a non-msaa
+ * context cannot be created. If preferCoreProfile is true but a core profile cannot be created
+ * then a compatible profile context will be created.
  */
 HGLRC SkCreateWGLContext(HDC dc, int msaaSampleCount, bool deepColor, SkWGLContextRequest context,
                          HGLRC shareContext = nullptr);
diff --git a/src/utils/win/SkWGL_win.cpp b/src/utils/win/SkWGL_win.cpp
index b7c89944e0..441d7a4ebb 100644
--- a/src/utils/win/SkWGL_win.cpp
+++ b/src/utils/win/SkWGL_win.cpp
@@ -126,6 +126,7 @@ int SkWGLExtensions::selectFormat(const int formats[],
                                   int formatCount,
                                   HDC dc,
                                   int desiredSampleCount) const {
+    SkASSERT(desiredSampleCount >= 1);
     if (formatCount <= 0) {
         return -1;
     }
@@ -146,7 +147,7 @@ int SkWGLExtensions::selectFormat(const int formats[],
                                      &kQueryAttr,
                                      &numSamples);
         rankedFormats[i].fFormat =  formats[i];
-        rankedFormats[i].fSampleCnt = numSamples;
+        rankedFormats[i].fSampleCnt = SkTMax(1, numSamples);
         rankedFormats[i].fChoosePixelFormatRank = i;
     }
     SkTQSort(rankedFormats.begin(),
@@ -159,6 +160,10 @@ int SkWGLExtensions::selectFormat(const int formats[],
     if (idx < 0) {
         idx = ~idx;
     }
+    // If the caller asked for non-MSAA fail if the closest format has MSAA.
+    if (desiredSampleCount == 1 && rankedFormats[idx].fSampleCnt != 1) {
+        return -1;
+    }
     return rankedFormats[idx].fFormat;
 }