Reopened: Caching the result of readPixelsSupported

src/gpu/gl/GrGLCaps.h

 /*
  * Copyright 2012 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 
 #ifndef GrGLCaps_DEFINED
 #define GrGLCaps_DEFINED
 
 #include "GrDrawTargetCaps.h"
 #include "GrGLStencilBuffer.h"
+#include "SkTHashCache.h"
 #include "SkTArray.h"
-#include "SkTDArray.h"
 
 class GrGLContextInfo;
 
 /**
  * Stores some capabilities of a GL context. Most are determined by the GL
  * version and the extensions string. It also tracks formats that have passed
  * the FBO completeness test.
  */
 class GrGLCaps : public GrDrawTargetCaps {
 public:
@@ skipping 220 matching lines @@
     bool vertexArrayObjectSupport() const { return fVertexArrayObjectSupport; }
 
     /// Use indices or vertices in CPU arrays rather than VBOs for dynamic content.
     bool useNonVBOVertexAndIndexDynamicData() const {
         return fUseNonVBOVertexAndIndexDynamicData;
     }
 
     /// Does ReadPixels support the provided format/type combo?
     bool readPixelsSupported(const GrGLInterface* intf,
                              GrGLenum format,
-                             GrGLenum type) const;
+                             GrGLenum type,
+                             GrGLenum currFboFormat) const;
 
     bool isCoreProfile() const { return fIsCoreProfile; }
 
 
     bool fullClearIsFree() const { return fFullClearIsFree; }
 
     bool dropsTileOnZeroDivide() const { return fDropsTileOnZeroDivide; }
 
     /**
      * Returns a string containing the caps info.
@@ skipping 50 matching lines @@
             return SkToBool(fVerifiedColorConfigs[u32Idx] & (1 << bitIdx));
         }
     };
 
     void initFSAASupport(const GrGLContextInfo&, const GrGLInterface*);
     void initStencilFormats(const GrGLContextInfo&);
     // This must be called after initFSAASupport().
     void initConfigRenderableTable(const GrGLContextInfo&);
     void initConfigTexturableTable(const GrGLContextInfo&, const GrGLInterface*);
 
+    bool doReadPixelsSupported(const GrGLInterface* intf,
+                                   GrGLenum format,
+                                   GrGLenum type) const;
+
     // tracks configs that have been verified to pass the FBO completeness when
     // used as a color attachment
     VerifiedColorConfigs fVerifiedColorConfigs;
 
     SkTArray<StencilFormat, true> fStencilFormats;
     // tracks configs that have been verified to pass the FBO completeness when
     // used as a color attachment when a particular stencil format is used
     // as a stencil attachment.
     SkTArray<VerifiedColorConfigs, true> fStencilVerifiedColorConfigs;
 
@@ skipping 20 matching lines @@
     bool fTextureRedSupport : 1;
     bool fImagingSupport  : 1;
     bool fTwoFormatLimit : 1;
     bool fFragCoordsConventionSupport : 1;
     bool fVertexArrayObjectSupport : 1;
     bool fUseNonVBOVertexAndIndexDynamicData : 1;
     bool fIsCoreProfile : 1;
     bool fFullClearIsFree : 1;
     bool fDropsTileOnZeroDivide : 1;
 
+    class ReadPixelsSupportedFormats {
+    public:
+        struct Key {
+            GrGLenum fFormat;
+            GrGLenum fType;
+            GrGLenum fFboFormat;
+
+            bool operator==(const Key& rhs) const {
+                return fFormat == rhs.fFormat
+                        && fType == rhs.fType
+                        && fFboFormat == rhs.fFboFormat;
+            }
+
+            uint32_t getHash() const {
+                // fFormat has different values like 0x190X or 0x8XXX: 16 bits are required
+                uint32_t hash = ((static_cast<uint32_t> (fFormat) & 0xFFFF) << 16);
+                // fType is 0x14XX: 8 lower bits are enough
+                hash |= ((static_cast<uint32_t> (fType) & 0xFF) << 8);
+                // fFboFormat is enum GrPixelConfig which has less than 15 values: 8 bits OK
+                hash |= (static_cast<uint32_t> (fFboFormat) & 0xFF);
+
+                return hash;

[mtklein, 2014/07/11 18:11:39]

You may have better results if you mix these bits.  As written, most of the time
only your low bits (from fFboFormat) are going to matter to the hash table.

  return SkChecksum::Mix(hash);

an alternative requiring even less thought is

uint32_t getHash() const {
  return SkChecksum::Murmur3(reinterpret_cast<const uint32_t*>(this),
sizeof(*this));
}

[Rémi Piotaix, 2014/07/14 20:38:59]

Done.

+            }
+        };
+
+        ReadPixelsSupportedFormats(Key key,

[mtklein, 2014/07/11 18:11:39]

Strange formatting?

[Rémi Piotaix, 2014/07/14 20:38:59]

Done.

+                bool value)
+        : fKey(key), fValue(value) {
+        }
+
+        static const Key& GetKey(const ReadPixelsSupportedFormats& element) {
+            return element.fKey;
+        }
+
+        static uint32_t Hash(const Key& key) {
+            return key.getHash();
+        }
+
+        bool value() const {
+            return fValue;
+        }
+    private:
+        Key fKey;
+        bool fValue;
+    };
+
+    mutable SkTHashCache<ReadPixelsSupportedFormats,
+                         ReadPixelsSupportedFormats::Key> fReadPixelsSupportedCache;
+
     typedef GrDrawTargetCaps INHERITED;
 };
 
 #endif