Add support for half float alpha textures.

tests/FloatingPointTextureTest.cpp

 /*
  * Copyright 2014 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 /*
  * This is a straightforward test of floating point textures, which are
  * supported on some platforms.  As of right now, this test only supports
  * 32 bit floating point textures, and indeed floating point test values
  * have been selected to require 32 bits of precision and full IEEE conformance
  */
 #if SK_SUPPORT_GPU
 #include <float.h>
 #include "Test.h"
 #include "GrContext.h"
 #include "GrTexture.h"
 #include "GrContextFactory.h"
+
 #include "SkGpuDevice.h"
+#include "SkHalf.h"
 
 static const int DEV_W = 100, DEV_H = 100;
-static const int FP_CONTROL_ARRAY_SIZE = DEV_W * DEV_H * sizeof(float);
+static const int FP_CONTROL_ARRAY_SIZE = DEV_W * DEV_H * 4;
 static const float kMaxIntegerRepresentableInSPFloatingPoint = 16777216;  // 2 ^ 24
 
 static const SkIRect DEV_RECT = SkIRect::MakeWH(DEV_W, DEV_H);
 
 DEF_GPUTEST(FloatingPointTextureTest, reporter, factory) {
     float controlPixelData[FP_CONTROL_ARRAY_SIZE];
     float readBuffer[FP_CONTROL_ARRAY_SIZE];
     for (int i = 0; i < FP_CONTROL_ARRAY_SIZE; i += 4) {
         controlPixelData[i] = FLT_MIN;
         controlPixelData[i + 1] = FLT_MAX;
@@ skipping 36 matching lines @@
             // write square
             fpTexture->writePixels(0, 0, DEV_W, DEV_H, desc.fConfig, controlPixelData, 0);
             fpTexture->readPixels(0, 0, DEV_W, DEV_H, desc.fConfig, readBuffer, 0);
             for (int j = 0; j < FP_CONTROL_ARRAY_SIZE; ++j) {
                 REPORTER_ASSERT(reporter, readBuffer[j] == controlPixelData[j]);
             }
         }
     }
 }
 
+static const int HALF_CONTROL_ARRAY_SIZE = DEV_W * DEV_H;
+
+DEF_GPUTEST(HalfFloatTextureTest, reporter, factory) {
+    SkHalf controlPixelData[HALF_CONTROL_ARRAY_SIZE];
+    SkHalf readBuffer[HALF_CONTROL_ARRAY_SIZE];
+    for (int i = 0; i < HALF_CONTROL_ARRAY_SIZE; i += 4) {
+        controlPixelData[i] = SK_HalfMin;
+        controlPixelData[i + 1] = SK_HalfMax;
+        controlPixelData[i + 2] = SK_HalfEpsilon;
+        controlPixelData[i + 3] = 0x6800;   // 2^11
+    }
+    
+    for (int origin = 0; origin < 2; ++origin) {
+        int glCtxTypeCnt = 1;
+        glCtxTypeCnt = GrContextFactory::kGLContextTypeCnt;
+        for (int glCtxType = 0; glCtxType < glCtxTypeCnt; ++glCtxType) {
+            GrSurfaceDesc desc;
+            desc.fFlags = kRenderTarget_GrSurfaceFlag;
+            desc.fWidth = DEV_W;
+            desc.fHeight = DEV_H;
+            desc.fConfig = kAlpha_half_GrPixelConfig;
+            desc.fOrigin = 0 == origin ?
+            kTopLeft_GrSurfaceOrigin : kBottomLeft_GrSurfaceOrigin;
+            
+            GrContext* context = NULL;
+            GrContextFactory::GLContextType type =
+            static_cast<GrContextFactory::GLContextType>(glCtxType);
+            if (!GrContextFactory::IsRenderingGLContext(type)) {
+                continue;
+            }
+            context = factory->get(type);
+            if (NULL == context){
+                continue;
+            }
+            
+            SkAutoTUnref<GrTexture> fpTexture(context->createUncachedTexture(desc,
+                                                                             NULL,
+                                                                             0));
+            
+            // 16-bit floating point textures are NOT supported everywhere
+            if (NULL == fpTexture) {
+                continue;
+            }
+            
+            // write square
+            fpTexture->writePixels(0, 0, DEV_W, DEV_H, desc.fConfig, controlPixelData, 0);
+            fpTexture->readPixels(0, 0, DEV_W, DEV_H, desc.fConfig, readBuffer, 0);
+            for (int j = 0; j < HALF_CONTROL_ARRAY_SIZE; ++j) {
+                SkASSERT(readBuffer[j] == controlPixelData[j]);
+                REPORTER_ASSERT(reporter, readBuffer[j] == controlPixelData[j]);
+            }
+        }
+    }
+}
+
 #endif