Use distance fields for glyphs > 256 pt, before switching to paths.

src/gpu/GrDistanceFieldTextContext.cpp

 /*
  * Copyright 2013 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #include "GrDistanceFieldTextContext.h"
 #include "GrAtlas.h"
 #include "GrBitmapTextContext.h"
@@ skipping 15 matching lines @@
 #include "SkPath.h"
 #include "SkRTConf.h"
 #include "SkStrokeRec.h"
 #include "effects/GrDistanceFieldTextureEffect.h"
 
 SK_CONF_DECLARE(bool, c_DumpFontCache, "gpu.dumpFontCache", false,
                 "Dump the contents of the font cache before every purge.");
 
 static const int kSmallDFFontSize = 32;
 static const int kSmallDFFontLimit = 32;
-static const int kMediumDFFontSize = 64;
-static const int kMediumDFFontLimit = 64;
-static const int kLargeDFFontSize = 128;
+static const int kMediumDFFontSize = 78;
+static const int kMediumDFFontLimit = 78;
+static const int kLargeDFFontSize = 192;
 
 static const int kVerticesPerGlyph = 4;
 static const int kIndicesPerGlyph = 6;
 
 GrDistanceFieldTextContext::GrDistanceFieldTextContext(GrContext* context,
                                                        const SkDeviceProperties& properties,
                                                        bool enable)
                                                     : GrTextContext(context, properties) {
 #if SK_FORCE_DISTANCE_FIELD_TEXT
     fEnableDFRendering = true;
@@ skipping 24 matching lines @@
     textContext->fFallbackTextContext = GrBitmapTextContext::Create(context, props);
 
     return textContext;
 }
 
 GrDistanceFieldTextContext::~GrDistanceFieldTextContext() {
     SkSafeSetNull(fGammaTexture);
 }
 
 bool GrDistanceFieldTextContext::canDraw(const SkPaint& paint, const SkMatrix& viewMatrix) {
-    if (!fEnableDFRendering && !paint.isDistanceFieldTextTEMP()) {
+    // TODO: support perspective (need getMaxScale replacement)
+    if (viewMatrix.hasPerspective()) {
         return false;
     }
 
+    SkScalar maxScale = viewMatrix.getMaxScale();
+    SkScalar scaledTextSize = maxScale*paint.getTextSize();
+    // Scaling up beyond 2x yields undesireable artifacts
+    if (scaledTextSize > 2*kLargeDFFontSize) {
+        return false;
+    }
+
+    if (!fEnableDFRendering && !paint.isDistanceFieldTextTEMP() &&
+        scaledTextSize < kLargeDFFontSize) {
+        return false;
+    }
+
     // rasterizers and mask filters modify alpha, which doesn't
     // translate well to distance
     if (paint.getRasterizer() || paint.getMaskFilter() ||
         !fContext->getTextTarget()->caps()->shaderDerivativeSupport()) {
         return false;
     }
 
     // TODO: add some stroking support
     if (paint.getStyle() != SkPaint::kFill_Style) {
         return false;
     }
 
-    // TODO: choose an appropriate maximum scale for distance fields and
-    //       enable perspective
-    if (SkDraw::ShouldDrawTextAsPaths(paint, viewMatrix)) {
-        return false;
-    }
-
     return true;
 }
 
 inline void GrDistanceFieldTextContext::init(const GrPaint& paint, const SkPaint& skPaint) {
     GrTextContext::init(paint, skPaint);
 
     fStrike = NULL;
 
     const SkMatrix& ctm = fViewMatrix;
 
@@ skipping 569 matching lines @@
     }
 }
 
 inline void GrDistanceFieldTextContext::finish() {
     this->flush();
     fTotalVertexCount = 0;
 
     GrTextContext::finish();
 }