Implement path cover with nv_path_rendering

src/gpu/GrStencilAndCoverPathRenderer.cpp

Index: src/gpu/GrStencilAndCoverPathRenderer.cpp
diff --git a/src/gpu/GrStencilAndCoverPathRenderer.cpp b/src/gpu/GrStencilAndCoverPathRenderer.cpp
index f7330a81f649246530ff3fa56162d83ecf3f854f..e745a2212c7ee3cb43ae1e1f26d0c68ce9c6ae26 100644
--- a/src/gpu/GrStencilAndCoverPathRenderer.cpp
+++ b/src/gpu/GrStencilAndCoverPathRenderer.cpp
@@ -17,7 +17,7 @@
 GrPathRenderer* GrStencilAndCoverPathRenderer::Create(GrContext* context) {
     SkASSERT(NULL != context);
     SkASSERT(NULL != context->getGpu());
-    if (context->getGpu()->caps()->pathStencilingSupport()) {
+    if (context->getGpu()->caps()->pathRenderingSupport()) {
         return SkNEW_ARGS(GrStencilAndCoverPathRenderer, (context->getGpu()));
     } else {
         return NULL;
@@ -25,7 +25,7 @@ GrPathRenderer* GrStencilAndCoverPathRenderer::Create(GrContext* context) {
 }
 
 GrStencilAndCoverPathRenderer::GrStencilAndCoverPathRenderer(GrGpu* gpu) {
-    SkASSERT(gpu->caps()->pathStencilingSupport());
+    SkASSERT(gpu->caps()->pathRenderingSupport());
     fGpu = gpu;
     gpu->ref();
 }
@@ -40,6 +40,8 @@ bool GrStencilAndCoverPathRenderer::canDrawPath(const SkPath& path,
                                                 bool antiAlias) const {
     return stroke.isFillStyle() &&
            !antiAlias && // doesn't do per-path AA, relies on the target having MSAA
+           !target->getDrawState().willEffectReadDstColor() && // not supported yet

[Chris Dalton, 2013/10/07 22:22:45]

I'm trying to understand why reading the dst color wouldn't be supported.

Doesn't the shader builder just add some fragment code and uniforms to look the
color up? AFAICT, this works without a vertex shader.

[Kimmo Kinnunen, 2013/10/08 12:14:09]

True, should've mentioned in commit msg that it is broken in other places.

I don't know if the fix is right.

[bsalomon, 2013/10/08 14:05:08]

Do you mean there are cases where requiring the dst color in an effect causes us
to draw incorrectly?

+           NULL != target->getDrawState().getRenderTarget()->getStencilBuffer() &&
            target->getDrawState().getStencil().isDisabled();
 }
 
@@ -70,27 +72,7 @@ bool GrStencilAndCoverPathRenderer::onDrawPath(const SkPath& path,
 
     SkAutoTUnref<GrPath> p(fGpu->createPath(path));
 
-    SkPath::FillType nonInvertedFill = SkPath::ConvertToNonInverseFillType(path.getFillType());
-    target->stencilPath(p, stroke, nonInvertedFill);
-
-    // TODO: Use built in cover operation rather than a rect draw. This will require making our
-    // fragment shaders be able to eat varyings generated by a matrix.
-
-    // fill the path, zero out the stencil
-    SkRect bounds = p->getBounds();
-    SkScalar bloat = drawState->getViewMatrix().getMaxStretch() * SK_ScalarHalf;
-    GrDrawState::AutoViewMatrixRestore avmr;
-
-    if (nonInvertedFill == path.getFillType()) {
-        GR_STATIC_CONST_SAME_STENCIL(kStencilPass,
-            kZero_StencilOp,
-            kZero_StencilOp,
-            kNotEqual_StencilFunc,
-            0xffff,
-            0x0000,
-            0xffff);
-        *drawState->stencil() = kStencilPass;
-    } else {
+    if (path.isInverseFillType()) {
         GR_STATIC_CONST_SAME_STENCIL(kInvertedStencilPass,
             kZero_StencilOp,
             kZero_StencilOp,
@@ -101,23 +83,22 @@ bool GrStencilAndCoverPathRenderer::onDrawPath(const SkPath& path,
             0xffff,
             0x0000,
             0xffff);
-        SkMatrix vmi;
-        bounds.setLTRB(0, 0,
-                       SkIntToScalar(drawState->getRenderTarget()->width()),
-                       SkIntToScalar(drawState->getRenderTarget()->height()));
-        // mapRect through persp matrix may not be correct
-        if (!drawState->getViewMatrix().hasPerspective() && drawState->getViewInverse(&vmi)) {
-            vmi.mapRect(&bounds);
-            // theoretically could set bloat = 0, instead leave it because of matrix inversion
-            // precision.
-        } else {
-            avmr.setIdentity(drawState);
-            bloat = 0;
-        }
+
         *drawState->stencil() = kInvertedStencilPass;
+    } else {
+        GR_STATIC_CONST_SAME_STENCIL(kStencilPass,
+            kZero_StencilOp,
+            kZero_StencilOp,
+            kNotEqual_StencilFunc,
+            0xffff,
+            0x0000,
+            0xffff);
+
+        *drawState->stencil() = kStencilPass;
     }
-    bounds.outset(bloat, bloat);
-    target->drawSimpleRect(bounds, NULL);
+
+    target->fillPath(p, stroke, path.getFillType());
+
     target->drawState()->stencil()->setDisabled();
     return true;
 }