Start the process of choosing the correct compression format

src/gpu/GrSWMaskHelper.cpp

Index: src/gpu/GrSWMaskHelper.cpp
diff --git a/src/gpu/GrSWMaskHelper.cpp b/src/gpu/GrSWMaskHelper.cpp
index 2e68b7829b4bde6f044b055df014cc94fd97d81f..be6eb034b432a15432444408b124589b6fbd465f 100644
--- a/src/gpu/GrSWMaskHelper.cpp
+++ b/src/gpu/GrSWMaskHelper.cpp
@@ -50,6 +50,37 @@ static inline GrPixelConfig fmt_to_config(SkTextureCompressor::Format fmt) {
     return configMap[fmt];
 }
 
+#if GR_COMPRESS_ALPHA_MASK
+static bool choose_compressed_fmt(const GrDrawTargetCaps* caps,
+                                  SkTextureCompressor::Format *fmt) {
+    if (NULL == fmt) {
+        return false;
+    }
+
+    // We can't use scratch textures without the ability to update
+    // compressed textures...
+    if (!(caps->compressedTexSubImageSupport())) {
+        return false;
+    }
+
+    // Figure out what our preferred texture type is. If ASTC is available, that always
+    // gives the biggest win. Otherwise, in terms of compression speed and accuracy,
+    // LATC has a slight edge over R11 EAC.
+    if (caps->isConfigTexturable(kASTC_12x12_GrPixelConfig)) {
+        *fmt = SkTextureCompressor::kASTC_12x12_Format;
+        return true;
+    } else if (caps->isConfigTexturable(kLATC_GrPixelConfig)) {
+        *fmt = SkTextureCompressor::kLATC_Format;
+        return true;
+    } else if (caps->isConfigTexturable(kR11_EAC_GrPixelConfig)) {
+        *fmt = SkTextureCompressor::kR11_EAC_Format;
+        return true;
+    }
+
+    return false;
+}
+#endif
+
 }
 
 /**
@@ -117,18 +148,23 @@ bool GrSWMaskHelper::init(const SkIRect& resultBounds,
                                      resultBounds.height());
 
 #if GR_COMPRESS_ALPHA_MASK
-    fCompressedFormat = SkTextureCompressor::kR11_EAC_Format;
+    fCompressMask = choose_compressed_fmt(fContext->getGpu()->caps(), &fCompressedFormat);
+#else
+    fCompressMask = false;
+#endif
 
     // Make sure that the width is a multiple of 16 so that we can use
     // specialized SIMD instructions that compress 4 blocks at a time.
-    int dimX, dimY;
-    SkTextureCompressor::GetBlockDimensions(fCompressedFormat, &dimX, &dimY);
-    const int cmpWidth = dimX * ((bounds.fRight + (dimX - 1)) / dimX);
-    const int cmpHeight = dimY * ((bounds.fBottom + (dimY - 1)) / dimY);
-#else
-    const int cmpWidth = bounds.fRight;
-    const int cmpHeight = bounds.fBottom;
-#endif
+    int cmpWidth, cmpHeight;
+    if (fCompressMask) {
+        int dimX, dimY;
+        SkTextureCompressor::GetBlockDimensions(fCompressedFormat, &dimX, &dimY);
+        cmpWidth = dimX * ((bounds.fRight + (dimX - 1)) / dimX);
+        cmpHeight = dimY * ((bounds.fBottom + (dimY - 1)) / dimY);
+    } else {
+        cmpWidth = bounds.fRight;
+        cmpHeight = bounds.fBottom;
+    }
 
     if (!fBM.allocPixels(SkImageInfo::MakeA8(cmpWidth, cmpHeight))) {
         return false;
@@ -153,25 +189,25 @@ bool GrSWMaskHelper::getTexture(GrAutoScratchTexture* texture) {
     GrTextureDesc desc;
     desc.fWidth = fBM.width();
     desc.fHeight = fBM.height();
+    desc.fConfig = kAlpha_8_GrPixelConfig;
 
-#if GR_COMPRESS_ALPHA_MASK
+    if (fCompressMask) {
 
 #ifdef SK_DEBUG
-    int dimX, dimY;
-    SkTextureCompressor::GetBlockDimensions(fCompressedFormat, &dimX, &dimY);
-    SkASSERT((desc.fWidth % dimX) == 0);
-    SkASSERT((desc.fHeight % dimY) == 0);
+        int dimX, dimY;
+        SkTextureCompressor::GetBlockDimensions(fCompressedFormat, &dimX, &dimY);
+        SkASSERT((desc.fWidth % dimX) == 0);
+        SkASSERT((desc.fHeight % dimY) == 0);
 #endif
 
-    desc.fConfig = fmt_to_config(fCompressedFormat);
+        desc.fConfig = fmt_to_config(fCompressedFormat);
 
-    // If this config isn't supported then we should fall back to A8
-    if (!(fContext->getGpu()->caps()->isConfigTexturable(desc.fConfig))) {
-        desc.fConfig = kAlpha_8_GrPixelConfig;
+        // If this config isn't supported then we should fall back to A8
+        if (!(fContext->getGpu()->caps()->isConfigTexturable(desc.fConfig))) {
+            SkDEBUGFAIL("Determining compression should be set from choose_compressed_fmt");
+            desc.fConfig = kAlpha_8_GrPixelConfig;
+        }
     }
-#else
-    desc.fConfig = kAlpha_8_GrPixelConfig;
-#endif
 
     texture->set(fContext, desc);
     return NULL != texture->texture();
@@ -195,23 +231,9 @@ void GrSWMaskHelper::sendTextureData(GrTexture *texture, const GrTextureDesc& de
 void GrSWMaskHelper::compressTextureData(GrTexture *texture, const GrTextureDesc& desc) {
 
     SkASSERT(GrPixelConfigIsCompressed(desc.fConfig));
+    SkASSERT(fmt_to_config(fCompressedFormat) == desc.fConfig);
 
-    SkTextureCompressor::Format format = SkTextureCompressor::kLATC_Format;
-
-    // Choose the format required by the texture descriptor.
-    switch(desc.fConfig) {
-        case kLATC_GrPixelConfig:
-            format = SkTextureCompressor::kLATC_Format;
-            break;
-        case kR11_EAC_GrPixelConfig:
-            format = SkTextureCompressor::kR11_EAC_Format;
-            break;
-        default:
-            SkFAIL("Unrecognized texture compression format.");
-            break;
-    }
-
-    SkAutoDataUnref cmpData(SkTextureCompressor::CompressBitmapToFormat(fBM, format));
+    SkAutoDataUnref cmpData(SkTextureCompressor::CompressBitmapToFormat(fBM, fCompressedFormat));
     SkASSERT(NULL != cmpData);
 
     this->sendTextureData(texture, desc, cmpData->data(), 0);
@@ -229,7 +251,7 @@ void GrSWMaskHelper::toTexture(GrTexture *texture) {
     desc.fConfig = texture->config();
         
     // First see if we should compress this texture before uploading.
-    if (GrPixelConfigIsCompressed(texture->config())) {
+    if (fCompressMask) {
         this->compressTextureData(texture, desc);
     } else {
         // Looks like we have to send a full A8 texture.