Decouple contrast boost from fake gamma.

src/core/SkPaint.cpp

Index: src/core/SkPaint.cpp
diff --git a/src/core/SkPaint.cpp b/src/core/SkPaint.cpp
index 8bd386a762a201d4e9adb4121a272e220ddbcc45..d05742df2b1b48ce6383007507e71a774540fe2c 100644
--- a/src/core/SkPaint.cpp
+++ b/src/core/SkPaint.cpp
@@ -959,7 +959,7 @@ SkScalar SkPaint::getFontMetrics(FontMetrics* metrics, SkScalar zoom) const {
         metrics = &storage;
     }
 
-    paint.descriptorProc(nullptr, FakeGamma::Off, zoomPtr, FontMetricsDescProc, metrics);
+    paint.descriptorProc(nullptr, kNone_ScalerContextFlags, zoomPtr, FontMetricsDescProc, metrics);
 
     if (scale) {
         metrics->fTop = SkScalarMul(metrics->fTop, scale);
@@ -1516,8 +1516,8 @@ void SkScalerContext::PostMakeRec(const SkPaint&, SkScalerContext::Rec* rec) {
             break;
         }
         case SkMask::kBW_Format:
-            // No need to differentiate gamma if we're BW
-            rec->ignorePreBlend();
+            // No need to differentiate gamma or apply contrast if we're BW
+            rec->ignorePreBlend(false);

[bungeman-skia, 2016/04/07 20:15:45]

At the call site it's annoying that the bool parameter is non-descriptively
'false'. We could make this an enum, or we could split this into ignoreGamma and
setContrast(0), with ignorePreBlend calling both ignoreGamma and setContrast(0).
That way all of these ignorePreBlend(false) turn into ignorePreBlend(). Then in
fill_out_rec, the current ignorePreBlend becomes ignoreGamma, and then adds 'if
(boostContrast) { setContrast(0); }' right after.

[Brian Osman, 2016/04/07 21:23:46]

Done. (Yeah, I like the broken-out API better).

             break;
     }
 }
@@ -1551,14 +1551,14 @@ static void write_out_descriptor(SkDescriptor* desc, const SkScalerContext::Rec&
 
 static size_t fill_out_rec(const SkPaint& paint, SkScalerContext::Rec* rec,
                            const SkSurfaceProps* surfaceProps,
-                           bool fakeGamma,
+                           bool fakeGamma, bool boostContrast,
                            const SkMatrix* deviceMatrix,
                            const SkPathEffect* pe, SkWriteBuffer* peBuffer,
                            const SkMaskFilter* mf, SkWriteBuffer* mfBuffer,
                            const SkRasterizer* ra, SkWriteBuffer* raBuffer) {
     SkScalerContext::MakeRec(paint, surfaceProps, deviceMatrix, rec);
     if (!fakeGamma) {
-        rec->ignorePreBlend();
+        rec->ignorePreBlend(boostContrast);
     }
 
     int entryCount = 1;
@@ -1580,7 +1580,7 @@ static size_t fill_out_rec(const SkPaint& paint, SkScalerContext::Rec* rec,
            The primary filter is blur, for which contrast makes no sense,
            and for which the destination guess error is more visible.
            Also, all existing users of blur have calibrated for linear. */
-        rec->ignorePreBlend();
+        rec->ignorePreBlend(false);
     }
     if (ra) {
         raBuffer->writeFlattenable(ra);
@@ -1647,7 +1647,7 @@ static void test_desc(const SkScalerContext::Rec& rec,
 /* see the note on ignoreGamma on descriptorProc */
 void SkPaint::getScalerContextDescriptor(SkAutoDescriptor* ad,
                                          const SkSurfaceProps& surfaceProps,
-                                         FakeGamma fakeGamma,
+                                         uint32_t scalerContextFlags,
                                          const SkMatrix* deviceMatrix) const {
     SkScalerContext::Rec    rec;
 
@@ -1656,9 +1656,10 @@ void SkPaint::getScalerContextDescriptor(SkAutoDescriptor* ad,
     SkRasterizer*   ra = this->getRasterizer();
 
     SkWriteBuffer   peBuffer, mfBuffer, raBuffer;
-    size_t descSize = fill_out_rec(*this, &rec,
-                                   &surfaceProps, FakeGamma::On == fakeGamma, deviceMatrix,
-                                   pe, &peBuffer, mf, &mfBuffer, ra, &raBuffer);
+    size_t descSize = fill_out_rec(*this, &rec, &surfaceProps,
+                                   SkToBool(scalerContextFlags & kFakeGamma_ScalerContextFlag),
+                                   SkToBool(scalerContextFlags & kBoostContrast_ScalerContextFlag),
+                                   deviceMatrix, pe, &peBuffer, mf, &mfBuffer, ra, &raBuffer);
 
     ad->reset(descSize);
     SkDescriptor* desc = ad->getDesc();
@@ -1678,7 +1679,7 @@ void SkPaint::getScalerContextDescriptor(SkAutoDescriptor* ad,
  *  contrast = 0, luminanceColor = transparent black.
  */
 void SkPaint::descriptorProc(const SkSurfaceProps* surfaceProps,
-                             FakeGamma fakeGamma,
+                             uint32_t scalerContextFlags,
                              const SkMatrix* deviceMatrix,
                              void (*proc)(SkTypeface*, const SkDescriptor*, void*),
                              void* context) const {
@@ -1689,9 +1690,10 @@ void SkPaint::descriptorProc(const SkSurfaceProps* surfaceProps,
     SkRasterizer*   ra = this->getRasterizer();
 
     SkWriteBuffer   peBuffer, mfBuffer, raBuffer;
-    size_t descSize = fill_out_rec(*this, &rec,
-                                   surfaceProps, FakeGamma::On == fakeGamma, deviceMatrix,
-                                   pe, &peBuffer, mf, &mfBuffer, ra, &raBuffer);
+    size_t descSize = fill_out_rec(*this, &rec, surfaceProps,
+                                   SkToBool(scalerContextFlags & kFakeGamma_ScalerContextFlag),
+                                   SkToBool(scalerContextFlags & kBoostContrast_ScalerContextFlag),
+                                   deviceMatrix, pe, &peBuffer, mf, &mfBuffer, ra, &raBuffer);
 
     SkAutoDescriptor    ad(descSize);
     SkDescriptor*       desc = ad.getDesc();
@@ -1708,10 +1710,10 @@ void SkPaint::descriptorProc(const SkSurfaceProps* surfaceProps,
 }
 
 SkGlyphCache* SkPaint::detachCache(const SkSurfaceProps* surfaceProps,
-                                   FakeGamma fakeGamma,
+                                   uint32_t scalerContextFlags,
                                    const SkMatrix* deviceMatrix) const {
     SkGlyphCache* cache;
-    this->descriptorProc(surfaceProps, fakeGamma, deviceMatrix, DetachDescProc, &cache);
+    this->descriptorProc(surfaceProps, scalerContextFlags, deviceMatrix, DetachDescProc, &cache);
     return cache;
 }
 
@@ -2246,7 +2248,9 @@ SkTextBaseIter::SkTextBaseIter(const char text[], size_t length,
         fPaint.setPathEffect(nullptr);
     }
 
-    fCache = fPaint.detachCache(nullptr, SkPaint::FakeGamma::On, nullptr);
+    // SRGBTODO: Is this correct?
+    fCache = fPaint.detachCache(nullptr, SkPaint::kFakeGammaAndBoostContrast_ScalerContextFlags,
+                                nullptr);
 
     SkPaint::Style  style = SkPaint::kFill_Style;
     sk_sp<SkPathEffect> pe;