More prep work in Gr for landing AA hairline renderer.

Review URL: http://codereview.appspot.com/4944045



git-svn-id: http://skia.googlecode.com/svn/trunk@2164 2bbb7eff-a529-9590-31e7-b0007b416f81

gpu/include/GrContext.h

@@ -182,7 +182,9 @@ public:
     /**
      *  Returns true if the specified use of an indexed texture is supported.
      */
-    bool supportsIndex8PixelConfig(const GrSamplerState&, int width, int height);
+    bool supportsIndex8PixelConfig(const GrSamplerState&,
+                                   int width,
+                                   int height) const;
 
     /**
      *  Return the current texture cache limits.
@@ -386,6 +388,11 @@ public:
     ///////////////////////////////////////////////////////////////////////////
     // Misc.
 
+    /**
+     * Currently needed by SkGpuDevice. Ideally this shouldn't be exposed.
+     */
+    bool supportsShaders() const;
+
     /**
      * Flags that affect flush() behavior.
      */
@@ -510,6 +517,7 @@ public:
     ///////////////////////////////////////////////////////////////////////////
     // Functions intended for internal use only.
     GrGpu* getGpu() { return fGpu; }
+    const GrGpu* getGpu() const { return fGpu; }
     GrFontCache* getFontCache() { return fFontCache; }
     GrDrawTarget* getTextTarget(const GrPaint& paint);
     void flushText();

gpu/include/GrSamplerState.h

@@ -31,7 +31,8 @@ public:
          * Average of 4 bilinear filterings spaced +/- 1 texel from sample
          * position in x and y. Intended for averaging 16 texels in a downsample
          * pass. (rasterizing such that texture samples fall exactly halfway
-         * between texels in x and y spaced 4 texels apart.)
+         * between texels in x and y spaced 4 texels apart.) Only supported
+         * on shader backends.
          */
         k4x4Downsample_Filter,
         /**

gpu/src/GrContext.cpp

@@ -551,7 +551,7 @@ GrResource* GrContext::createPlatformSurface(const GrPlatformSurfaceDesc& desc)
 ///////////////////////////////////////////////////////////////////////////////
 
 bool GrContext::supportsIndex8PixelConfig(const GrSamplerState& sampler,
-                                          int width, int height) {
+                                          int width, int height) const {
     if (!fGpu->supports8BitPalette()) {
         return false;
     }
@@ -639,7 +639,10 @@ bool GrContext::doOffscreenAA(GrDrawTarget* target,
     if (!paint.fAntiAlias) {
         return false;
     }
-    if (isHairLines && target->willUseHWAALines()) {
+    // Line primitves are always rasterized as 1 pixel wide.
+    // Super-sampling would make them too thin but MSAA would be OK.
+    if (isHairLines &&
+        (!PREFER_MSAA_OFFSCREEN_AA || !fGpu->supportsFullsceneAA())) {
         return false;
     }
     if (target->getRenderTarget()->isMultisampled()) {
@@ -693,7 +696,7 @@ bool GrContext::prepareForOffscreenAA(GrDrawTarget* target,
         record->fScale = 1;
         desc.fAALevel = kMed_GrAALevel;
     } else {
-        record->fDownsample = (fGpu->supports4x4DownsampleFilter()) ?
+        record->fDownsample = (fGpu->supportsShaders()) ?
                                 OffscreenRecord::k4x4SinglePass_Downsample :
                                 OffscreenRecord::k4x4TwoPass_Downsample;
         record->fScale = OFFSCREEN_SSAA_SCALE;
@@ -1492,6 +1495,10 @@ void GrContext::drawPath(const GrPaint& paint, const GrPath& path,
 
 ////////////////////////////////////////////////////////////////////////////////
 
+bool GrContext::supportsShaders() const {
+    return fGpu->supportsShaders();
+}
+
 void GrContext::flush(int flagsBitfield) {
     if (kDiscard_FlushBit & flagsBitfield) {
         fDrawBuffer->reset();

gpu/src/GrGpu.h

@@ -183,6 +183,16 @@ public:
      */
     bool supportsHWAALines() const { return fAALineSupport; }
 
+    /**
+     * Are shaders supported.
+     */
+    bool supportsShaders() const { return fShaderSupport; }
+
+    /**
+     * Are derivative instructions supported in fragment shaders
+     */
+    bool supportsShaderDerivatives() const { return fShaderDerivativeSupport; }
+
     /**
      * Does the subclass support GrSamplerState::k4x4Downsample_Filter
      */
@@ -363,6 +373,8 @@ protected:
     bool fTwoSidedStencilSupport;
     bool fStencilWrapOpsSupport;
     bool fAALineSupport;
+    bool fShaderSupport;
+    bool fShaderDerivativeSupport;
     bool fFSAASupport;
     bool f4X4DownsampleFilterSupport; // supports GrSamplerState::k4x4Downsample_Filter
     bool fDualSourceBlendingSupport;

gpu/src/GrGpuGLFixed.cpp

@@ -62,7 +62,8 @@ GrGLBinding get_binding_in_use(const GrGLInterface* gl) {
 
 GrGpuGLFixed::GrGpuGLFixed(const GrGLInterface* gl)
     : GrGpuGL(gl, get_binding_in_use(gl)) {
-    f4X4DownsampleFilterSupport = false;
+    fShaderSupport = false;
+    fShaderDerivativeSupport = false;
     fDualSourceBlendingSupport = false;
 }
 

gpu/src/GrGpuGLShaders.cpp

@@ -256,13 +256,16 @@ GrGLBinding get_binding_in_use(const GrGLInterface* gl) {
 GrGpuGLShaders::GrGpuGLShaders(const GrGLInterface* gl)
     : GrGpuGL(gl, get_binding_in_use(gl)) {
 
-    f4X4DownsampleFilterSupport = true;
+    fShaderSupport = true;
     if (kDesktop_GrGLBinding == this->glBinding()) {
         fDualSourceBlendingSupport =
                             fGLVersion >= 3.3f ||
                             this->hasExtension("GL_ARB_blend_func_extended");
+        fShaderDerivativeSupport = true;
     } else {
         fDualSourceBlendingSupport = false;
+        fShaderDerivativeSupport =
+                            this->hasExtension("GL_OES_standard_derivatives");
     }
 
     fProgramData = NULL;

src/gpu/SkGpuDevice.cpp

@@ -694,7 +694,8 @@ static bool drawWithGPUMaskFilter(GrContext* context, const SkPath& path,
 #endif
     SkMaskFilter::BlurInfo info;
     SkMaskFilter::BlurType blurType = filter->asABlur(&info);
-    if (SkMaskFilter::kNone_BlurType == blurType) {
+    if (SkMaskFilter::kNone_BlurType == blurType ||
+        !context->supportsShaders()) {
         return false;
     }
     SkScalar radius = info.fIgnoreTransform ? info.fRadius