Add flag for window rectangles to GrRenderTarget

Adds a flag to GrRenderTarget that indicates whether it can be used
with window rectangles. Also attempts to clean up some of the mixed
samples API.

BUG=skia:
GOLD_TRYBOT_URL= https://gold.skia.org/search?issue=2225303002

Review-Url: https://codereview.chromium.org/2225303002

3 files changed, 43 insertions, 61 deletions

diff --git a/include/gpu/GrDrawContext.h b/include/gpu/GrDrawContext.h
index 6b582a6a63..def541d9a9 100644
--- a/include/gpu/GrDrawContext.h
+++ b/include/gpu/GrDrawContext.h
@@ -263,7 +263,7 @@ public:
         return fRenderTarget->isStencilBufferMultisampled();
     }
     bool isUnifiedMultisampled() const { return fRenderTarget->isUnifiedMultisampled(); }
-    bool hasMixedSamples() const { return fRenderTarget->hasMixedSamples(); }
+    bool hasMixedSamples() const { return fRenderTarget->isMixedSampled(); }
 
     bool mustUseHWAA(const GrPaint& paint) const {
         return paint.isAntiAlias() && fRenderTarget->isUnifiedMultisampled();
diff --git a/include/gpu/GrRenderTarget.h b/include/gpu/GrRenderTarget.h
index 77b04d24d3..1f87787d45 100644
--- a/include/gpu/GrRenderTarget.h
+++ b/include/gpu/GrRenderTarget.h
@@ -30,66 +30,28 @@ public:
     const GrRenderTarget* asRenderTarget() const  override { return this; }
 
     // GrRenderTarget
-    /**
-     * On some hardware it is possible for a render target to have multisampling
-     * only in certain buffers.
-     * Enforce only two legal sample configs.
-     * kUnified_SampleConfig signifies multisampling in both color and stencil
-     * buffers and is available across all hardware.
-     * kStencil_SampleConfig means multisampling is present in stencil buffer
-     * only; this config requires hardware support of
-     * NV_framebuffer_mixed_samples.
-    */
-    enum SampleConfig {
-        kUnified_SampleConfig = 0,
-        kStencil_SampleConfig = 1
-    };
-
-    /**
-     * @return true if the surface is multisampled in all buffers,
-     *         false otherwise
-     */
-    bool isUnifiedMultisampled() const {
-        if (fSampleConfig != kUnified_SampleConfig) {
-            return false;
-        }
-        return 0 != fDesc.fSampleCnt;
-    }
+    bool isStencilBufferMultisampled() const { return fDesc.fSampleCnt > 0; }
 
     /**
-     * @return true if the surface is multisampled in the stencil buffer,
-     *         false otherwise
+     * For our purposes, "Mixed Sampled" means the stencil buffer is multisampled but the color
+     * buffer is not.
      */
-    bool isStencilBufferMultisampled() const {
-        return 0 != fDesc.fSampleCnt;
-    }
+    bool isMixedSampled() const { return fFlags & Flags::kMixedSampled; }
 
     /**
-     * @return the number of color samples-per-pixel, or zero if non-MSAA or
-     *         multisampled in the stencil buffer only.
+     * "Unified Sampled" means the stencil and color buffers are both multisampled.
      */
-    int numColorSamples() const {
-        if (fSampleConfig == kUnified_SampleConfig) {
-            return fDesc.fSampleCnt;
-        }
-        return 0;
-    }
+    bool isUnifiedMultisampled() const { return fDesc.fSampleCnt > 0 && !this->isMixedSampled(); }
 
     /**
-     * @return the number of stencil samples-per-pixel, or zero if non-MSAA.
+     * Returns the number of samples/pixel in the stencil buffer (Zero if non-MSAA).
      */
-    int numStencilSamples() const {
-        return fDesc.fSampleCnt;
-    }
+    int numStencilSamples() const { return fDesc.fSampleCnt; }
 
     /**
-     * @return true if the surface is mixed sampled, false otherwise.
+     * Returns the number of samples/pixel in the color buffer (Zero if non-MSAA or mixed sampled).
      */
-    bool hasMixedSamples() const {
-        SkASSERT(kStencil_SampleConfig != fSampleConfig ||
-                 this->isStencilBufferMultisampled());
-        return kStencil_SampleConfig == fSampleConfig;
-    }
+    int numColorSamples() const { return this->isMixedSampled() ? 0 : fDesc.fSampleCnt; }
 
     /**
      * Call to indicate the multisample contents were modified such that the
@@ -156,19 +118,17 @@ public:
     void setLastDrawTarget(GrDrawTarget* dt);
     GrDrawTarget* getLastDrawTarget() { return fLastDrawTarget; }
 
-    static SampleConfig ComputeSampleConfig(const GrCaps& caps, int sampleCnt);
-
 protected:
-    GrRenderTarget(GrGpu* gpu, const GrSurfaceDesc& desc,
-                   SampleConfig sampleConfig, GrStencilAttachment* stencil = nullptr)
-        : INHERITED(gpu, desc)
-        , fStencilAttachment(stencil)
-        , fMultisampleSpecsID(0)
-        , fSampleConfig(sampleConfig)
-        , fLastDrawTarget(nullptr) {
-        fResolveRect.setLargestInverted();
-    }
+    enum class Flags {
+        kNone                = 0,
+        kMixedSampled        = 1 << 0,
+        kWindowRectsSupport  = 1 << 1
+    };
+
+    GR_DECL_BITFIELD_CLASS_OPS_FRIENDS(Flags);
 
+    GrRenderTarget(GrGpu*, const GrSurfaceDesc&, Flags = Flags::kNone,
+                   GrStencilAttachment* = nullptr);
     ~GrRenderTarget() override;
 
     // override of GrResource
@@ -186,7 +146,7 @@ private:
 
     GrStencilAttachment*  fStencilAttachment;
     uint8_t               fMultisampleSpecsID;
-    SampleConfig          fSampleConfig;
+    Flags                 fFlags;
 
     SkIRect               fResolveRect;
 
@@ -201,5 +161,6 @@ private:
     typedef GrSurface INHERITED;
 };
 
+GR_MAKE_BITFIELD_CLASS_OPS(GrRenderTarget::Flags);
 
 #endif
diff --git a/include/gpu/GrTypes.h b/include/gpu/GrTypes.h
index a0f13aa6fe..7bc949d73c 100644
--- a/include/gpu/GrTypes.h
+++ b/include/gpu/GrTypes.h
@@ -49,6 +49,27 @@
     \
     template <typename T> \
     friend X operator & (X a, T b); \
+
+/**
+ * Defines bitwise operators that make it possible to use an enum class as a
+ * very basic bitfield.
+ */
+#define GR_MAKE_BITFIELD_CLASS_OPS(X) \
+    inline X operator | (X a, X b) { \
+        return (X) ((int)a | (int)b); \
+    } \
+    inline X& operator |= (X& a, X b) { \
+        return (a = a | b); \
+    } \
+    inline bool operator & (X a, X b) { \
+        return SkToBool((int)a & (int)b); \
+    }
+
+#define GR_DECL_BITFIELD_CLASS_OPS_FRIENDS(X) \
+    friend X operator | (X a, X b); \
+    friend X& operator |= (X& a, X b); \
+    friend bool operator & (X a, X b);
+
 ////////////////////////////////////////////////////////////////////////////////
 
 // compile time versions of min/max