Implement path cover with nv_path_rendering

src/gpu/GrStencilAndCoverPathRenderer.cpp

 
 /*
  * Copyright 2012 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 
 #include "GrStencilAndCoverPathRenderer.h"
 #include "GrContext.h"
 #include "GrDrawTargetCaps.h"
 #include "GrGpu.h"
 #include "GrPath.h"
 #include "SkStrokeRec.h"
 
 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;
     }
 }
 
 GrStencilAndCoverPathRenderer::GrStencilAndCoverPathRenderer(GrGpu* gpu) {
-    SkASSERT(gpu->caps()->pathStencilingSupport());
+    SkASSERT(gpu->caps()->pathRenderingSupport());
     fGpu = gpu;
     gpu->ref();
 }
 
 GrStencilAndCoverPathRenderer::~GrStencilAndCoverPathRenderer() {
     fGpu->unref();
 }
 
 bool GrStencilAndCoverPathRenderer::canDrawPath(const SkPath& path,
                                                 const SkStrokeRec& stroke,
                                                 const GrDrawTarget* target,
                                                 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();
 }
 
 GrPathRenderer::StencilSupport GrStencilAndCoverPathRenderer::onGetStencilSupport(
                                                         const SkPath&,
                                                         const SkStrokeRec& ,
                                                         const GrDrawTarget*) const {
     return GrPathRenderer::kStencilOnly_StencilSupport;
 }
 
@@ skipping 10 matching lines @@
                                                GrDrawTarget* target,
                                                bool antiAlias) {
     SkASSERT(!antiAlias);
     SkASSERT(!stroke.isHairlineStyle());
 
     GrDrawState* drawState = target->drawState();
     SkASSERT(drawState->getStencil().isDisabled());
 
     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,
             // We know our rect will hit pixels outside the clip and the user bits will be 0
             // outside the clip. So we can't just fill where the user bits are 0. We also need to
             // check that the clip bit is set.
             kEqualIfInClip_StencilFunc,
             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;
 }