Reopened: Caching the result of readPixelsSupported

src/gpu/gl/GrGLCaps.cpp

Index: src/gpu/gl/GrGLCaps.cpp
diff --git a/src/gpu/gl/GrGLCaps.cpp b/src/gpu/gl/GrGLCaps.cpp
index 4a62c5acaab1ce370545f9b11d991153260d0e3f..9f0c121e4591d6001d8335cd9e642c50201fef58 100644
--- a/src/gpu/gl/GrGLCaps.cpp
+++ b/src/gpu/gl/GrGLCaps.cpp
@@ -48,6 +48,8 @@ void GrGLCaps::reset() {
     fIsCoreProfile = false;
     fFullClearIsFree = false;
     fDropsTileOnZeroDivide = false;
+
+    fReadPixelsSupportedCache.clear();
 }
 
 GrGLCaps::GrGLCaps(const GrGLCaps& caps) : GrDrawTargetCaps() {
@@ -485,7 +487,7 @@ void GrGLCaps::initConfigTexturableTable(const GrGLContextInfo& ctxInfo, const G
     // First check version for support
     if (kGL_GrGLStandard == standard) {
         hasETC1 = hasCompressTex2D &&
-            (version >= GR_GL_VER(4, 3) || 
+            (version >= GR_GL_VER(4, 3) ||
              ctxInfo.hasExtension("GL_ARB_ES3_compatibility"));
     } else {
         hasETC1 = hasCompressTex2D &&
@@ -541,9 +543,9 @@ void GrGLCaps::initConfigTexturableTable(const GrGLContextInfo& ctxInfo, const G
     }
 }
 
-bool GrGLCaps::readPixelsSupported(const GrGLInterface* intf,
-                                   GrGLenum format,
-                                   GrGLenum type) const {
+bool GrGLCaps::doReadPixelsSupported(const GrGLInterface* intf,
+                                     GrGLenum format,
+                                     GrGLenum type) const {
     if (GR_GL_RGBA == format && GR_GL_UNSIGNED_BYTE == type) {
         // ES 2 guarantees this format is supported
         return true;
@@ -570,6 +572,24 @@ bool GrGLCaps::readPixelsSupported(const GrGLInterface* intf,
     return (GrGLenum)otherFormat == format && (GrGLenum)otherType == type;
 }
 
+bool GrGLCaps::readPixelsSupported(const GrGLInterface* intf,
+                                   GrGLenum format,
+                                   GrGLenum type,
+                                   GrGLenum currFboFormat) const {
+
+    ReadPixelsSupportedFormatsKey key = {format, type, currFboFormat};
+
+    ReadPixelsSupportedFormats* cachedValue = fReadPixelsSupportedCache.find(key);
+
+    if (NULL == cachedValue) {
+        bool value = doReadPixelsSupported(intf, format, type);
+        cachedValue = new ReadPixelsSupportedFormats(key, value);
+        fReadPixelsSupportedCache.put(cachedValue);
+    }
+
+    return cachedValue->value();
+}
+
 void GrGLCaps::initFSAASupport(const GrGLContextInfo& ctxInfo, const GrGLInterface* gli) {
 
     fMSFBOType = kNone_MSFBOType;
@@ -798,3 +818,17 @@ SkString GrGLCaps::dump() const {
     r.appendf("Drops tile on zero divide: %s\n", (fDropsTileOnZeroDivide ? "YES" : "NO"));
     return r;
 }
+
+//Computes a hash based on the three values in the key struct
+// bits 31------------15---------7---------------0
+//      fFormat(15:0) fType(7:0) fFboFormat(7:0)
+uint32_t GrGLCaps::ReadPixelsSupportedFormats::Hash(const ReadPixelsSupportedFormatsKey& key) {
+    // fFormat has different values like 0x190X or 0x8XXX: 16 bits are required
+    uint32_t hash = ((static_cast<uint32_t>(key.fFormat) & 0xFFFF) << 16);
+    // fType is 0x14XX: 8 lower bits are enough
+    hash |= ((static_cast<uint32_t>(key.fType) & 0xFF) << 8);
+    // fFboFormat is enum GrPixelConfig which has less than 15 values: 8 bits OK
+    hash |= (static_cast<uint32_t>(key.fFboFormat) & 0xFF);
+
+    return hash;
+}