Improved distance field sampling

src/gpu/GrDistanceFieldTextContext.cpp

Index: src/gpu/GrDistanceFieldTextContext.cpp
diff --git a/src/gpu/GrDistanceFieldTextContext.cpp b/src/gpu/GrDistanceFieldTextContext.cpp
index bd3927c648839232f655aaead473cee7a7892b21..077709fb78cfe548c1392a0d637fed832870f797 100755
--- a/src/gpu/GrDistanceFieldTextContext.cpp
+++ b/src/gpu/GrDistanceFieldTextContext.cpp
@@ -8,6 +8,7 @@
 #include "GrDistanceFieldTextContext.h"
 #include "GrAtlas.h"
 #include "GrDrawTarget.h"
+#include "GrDrawTargetCaps.h"
 #include "GrFontScaler.h"
 #include "SkGlyphCache.h"
 #include "GrIndexBuffer.h"
@@ -21,6 +22,7 @@
 #include "effects/GrDistanceFieldTextureEffect.h"
 
 static const int kGlyphCoordsAttributeIndex = 1;
+static const int kGlyphOffsetAttributeIndex = 2;
 
 static const int kBaseDFFontSize = 32;
 
@@ -46,6 +48,7 @@ GrDistanceFieldTextContext::~GrDistanceFieldTextContext() {
 bool GrDistanceFieldTextContext::canDraw(const SkPaint& paint) {
     return !paint.getRasterizer() && !paint.getMaskFilter() &&
            paint.getStyle() == SkPaint::kFill_Style &&
+           fContext->getTextTarget()->caps()->shaderDerivativeSupport() &&
            !SkDraw::ShouldDrawTextAsPaths(paint, fContext->getMatrix());
 }
 
@@ -67,14 +70,14 @@ void GrDistanceFieldTextContext::flushGlyphs() {
 
     if (fCurrVertex > 0) {
         // setup our sampler state for our text texture/atlas
-        SkASSERT(GrIsALIGN4(fCurrVertex));
+        SkASSERT(fCurrVertex % 6 == 0);
         SkASSERT(fCurrTexture);
         GrTextureParams params(SkShader::kRepeat_TileMode, GrTextureParams::kBilerp_FilterMode);
 
         // This effect could be stored with one of the cache objects (atlas?)
         drawState->addCoverageEffect(
                                 GrDistanceFieldTextureEffect::Create(fCurrTexture, params),
-                                kGlyphCoordsAttributeIndex)->unref();
+                                kGlyphCoordsAttributeIndex, kGlyphOffsetAttributeIndex)->unref();
 
         if (!GrPixelConfigIsAlphaOnly(fCurrTexture->config())) {
             if (kOne_GrBlendCoeff != fPaint.getSrcBlendCoeff() ||
@@ -98,7 +101,7 @@ void GrDistanceFieldTextContext::flushGlyphs() {
             drawState->setColor(fPaint.getColor());
         }
 
-        int nGlyphs = fCurrVertex / 4;
+        int nGlyphs = fCurrVertex / 6;
         fDrawTarget->setIndexSourceToBuffer(fContext->getQuadIndexBuffer());
         fDrawTarget->drawIndexedInstances(kTriangles_GrPrimitiveType,
                                           nGlyphs,
@@ -115,8 +118,9 @@ namespace {
 
 // position + texture coord
 extern const GrVertexAttrib gTextVertexAttribs[] = {
-    {kVec2f_GrVertexAttribType, 0,               kPosition_GrVertexAttribBinding},
-    {kVec2f_GrVertexAttribType, sizeof(GrPoint), kEffect_GrVertexAttribBinding}
+    {kVec2f_GrVertexAttribType, 0,                 kPosition_GrVertexAttribBinding},
+    {kVec2f_GrVertexAttribType, sizeof(GrPoint),   kEffect_GrVertexAttribBinding},
+    {kVec2f_GrVertexAttribType, 2*sizeof(GrPoint), kEffect_GrVertexAttribBinding}
 };
 
 };
@@ -248,7 +252,7 @@ HAS_ATLAS:
                                                                GrTCast<void**>(&fVertices),
                                                                NULL);
         GrAlwaysAssert(success);
-        SkASSERT(2*sizeof(GrPoint) == fDrawTarget->getDrawState().getVertexSize());
+        SkASSERT(3*sizeof(GrPoint) == fDrawTarget->getDrawState().getVertexSize());
     }
 
     SkScalar dx = SkIntToScalar(glyph->fBounds.fLeft);
@@ -263,23 +267,30 @@ HAS_ATLAS:
     sy += dy;
     width *= scale;
     height *= scale;
-
+     
     GrFixed tx = SkIntToFixed(glyph->fAtlasLocation.fX);
     GrFixed ty = SkIntToFixed(glyph->fAtlasLocation.fY);
     GrFixed tw = SkIntToFixed(glyph->fBounds.width());
     GrFixed th = SkIntToFixed(glyph->fBounds.height());
 
+    SkISize texSize = fStrike->getAtlasSize();

[bsalomon, 2014/02/05 20:19:10]

AFAICT this is the same for the lifetime of the program. Perhaps we should use a
uniform rather than a vertex attribute?

[jvanverth1, 2014/02/10 18:34:02]

Done.

+
     fVertices[2*fCurrVertex].setRectFan(sx,
                                         sy,
                                         sx + width,
                                         sy + height,
-                                        2 * sizeof(SkPoint));
+                                        3 * sizeof(SkPoint));

[bsalomon, 2014/02/05 20:19:10]

this 3 * sizeof(SkPoint) is repeated here three times and once above. Maybe

static const size_t kVertexSize = 3 * sizeof(SkPoint);

[jvanverth1, 2014/02/10 18:34:02]

Done.

     fVertices[2*fCurrVertex+1].setRectFan(SkFixedToFloat(texture->normalizeFixedX(tx)),
                                           SkFixedToFloat(texture->normalizeFixedY(ty)),
                                           SkFixedToFloat(texture->normalizeFixedX(tx + tw)),
                                           SkFixedToFloat(texture->normalizeFixedY(ty + th)),
-                                          2 * sizeof(SkPoint));
-    fCurrVertex += 4;
+                                          3 * sizeof(SkPoint));
+    fVertices[2*fCurrVertex+2].setRectFan(SkIntToScalar(texSize.fWidth),
+                                          SkIntToScalar(texSize.fHeight),
+                                          SkIntToScalar(texSize.fWidth),
+                                          SkIntToScalar(texSize.fHeight),
+                                          3 * sizeof(SkPoint));
+    fCurrVertex += 6;
 }
 
 inline void GrDistanceFieldTextContext::init(const GrPaint& paint, const SkPaint& skPaint) {