Move the GrGLGpu config stencil format index into ConfigTable

src/gpu/gl/GrGLGpu.h

Index: src/gpu/gl/GrGLGpu.h
diff --git a/src/gpu/gl/GrGLGpu.h b/src/gpu/gl/GrGLGpu.h
index 409aae8f43da64a3d11f35f7af5002b344ea43ca..4f3b37ee9dfac7de1612bf91b7e50d48d4b8c52b 100644
--- a/src/gpu/gl/GrGLGpu.h
+++ b/src/gpu/gl/GrGLGpu.h
@@ -153,7 +153,7 @@ private:
     GrRenderTarget* onWrapBackendRenderTarget(const GrBackendRenderTargetDesc&,
                                               GrWrapOwnership) override;
     // Given a GrPixelConfig return the index into the stencil format array on GrGLCaps to a
-    // compatible stencil format.
+    // compatible stencil format, or negative if there is no compatible stencil format.

[egdaniel, 2015/12/16 21:52:11]

Not a big issue, I can go either way, but would it make more sense to say:

"Given a GrPixelConfig return the index into the stencil format array on
GrGLCaps to a compatible stencil format, or
ConfigEntry::kUnsupported_StencilFormatIndex if there is no compatible stencil
format." We should never return kUnknown and this makes it very clear what
values can be returned from this function. If we go this route I would change
the if statement in createStencil back to what it was before.

[bsalomon, 2015/12/17 16:56:45]

My feeling is that kUnsupported and kUnimplemented are implementation details
and that if this code was in another class we might not expose kUnsupported or
kUnimplemented to the caller. I suppose we could expose kUnsupported only but
since the return value is an index it seems straightforward to me to say
anything negative means we failed to find a compatible format.

     int getCompatibleStencilIndex(GrPixelConfig config);
 
     void onClear(GrRenderTarget*, const SkIRect& rect, GrColor color) override;
@@ -541,18 +541,27 @@ private:
 
     struct ConfigEntry {
         // Default constructor inits to known bad GL enum values.
-        ConfigEntry() { memset(this, 0xAB, sizeof(ConfigEntry)); }
+        ConfigEntry() {
+            memset(this, 0xAB, sizeof(ConfigEntry));
+            fStencilFormatIndex = kUnknown_StencilIndex;
+        }
         GrGLenum fBaseInternalFormat;
         GrGLenum fSizedInternalFormat;
         GrGLenum fExternalFormat;
         GrGLenum fExternalType;
-    };
 
-    ConfigEntry fConfigTable[kLast_GrPixelConfig + 1];
+        // Index into GrGLCaps's list of stencil formats. Support is determined experimentally and
+        // lazily.
+        int      fStencilFormatIndex;
+        enum {
+            // This indicates that a stencil format has not yet been determined for the config.
+            kUnknown_StencilIndex = -1,
+            // This indicates that there is no supported stencil format for the config.
+            kUnsupported_StencilFormatIndex = -2
+        };
+    };
 
-    // Mapping of pixel configs to known supported stencil formats to be used
-    // when adding a stencil buffer to a framebuffer.
-    int fPixelConfigToStencilIndex[kGrPixelConfigCnt];
+    ConfigEntry fConfigTable[kGrPixelConfigCnt];
 
     typedef GrGpu INHERITED;
     friend class GrGLPathRendering; // For accessing setTextureUnit.