Adding code to calculate Underline Thickness from Font Metrics, this will be useful when Skia is us…

src/core/SkPaint.cpp

 
 /*
  * Copyright 2006 The Android Open Source Project
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #include "SkPaint.h"
 #include "SkAnnotation.h"
@@ skipping 1269 matching lines @@
     }
 
     FontMetrics storage;
     if (NULL == metrics) {
         metrics = &storage;
     }
 
     paint.descriptorProc(NULL, zoomPtr, FontMetricsDescProc, metrics, true);
 
     if (scale) {
+        // Assuming Font will have correct metrics for Underline Thickness and Position
+        metrics->fFontMetricsFlag = 0x03;
+
         metrics->fTop = SkScalarMul(metrics->fTop, scale);
         metrics->fAscent = SkScalarMul(metrics->fAscent, scale);
         metrics->fDescent = SkScalarMul(metrics->fDescent, scale);
         metrics->fBottom = SkScalarMul(metrics->fBottom, scale);
         metrics->fLeading = SkScalarMul(metrics->fLeading, scale);
         metrics->fAvgCharWidth = SkScalarMul(metrics->fAvgCharWidth, scale);
         metrics->fXMin = SkScalarMul(metrics->fXMin, scale);
         metrics->fXMax = SkScalarMul(metrics->fXMax, scale);
         metrics->fXHeight = SkScalarMul(metrics->fXHeight, scale);
+
+        metrics->fUnderlineThickness = SkScalarMul(metrics->fUnderlineThickness, scale);
+        // Following is to check if we have faulty underline thciness metrics
+        if ( (metrics->fUnderlineThickness == 0) || (metrics->fUnderlineThickness >= metrics->fAscent/2))

[bungeman-skia, 2014/02/17 19:10:06]

Why would these checks only be done when there is a 'scale'? These seem like odd
checks here in any event, it seems that the knowledge as to whether we actually
have good values should come from the port, not have some policy hard coded
here. If this is the sort of policy checks that, say, Blink would like, then
Blink should implement such a policy.

[h.joshi, 2014/02/18 05:48:48]

Added these to check faulty font metrics for Underline, as Underline is defined
for scaled fonts only so added check here, from previous comments I thought Skia
needs to check if Font has faulty Underline metrics and then set respective
flag.

On 2014/02/17 19:10:06, bungeman1 wrote:

+        {
+            metrics->fFontMetricsFlag = metrics->fFontMetricsFlag  ^ FontMetrics::kUnderlineThinknessIsValid_FontMetricFlag;
+        }
+
+        metrics->fUnderlinePosition = SkScalarMul(metrics->fUnderlinePosition, scale);
+        // Following is to check if we have faulty underlien position metrics
+        if(SkScalarAbs(metrics->fUnderlinePosition) >= (metrics->fDescent + metrics->fLeading))
+        {
+            metrics->fFontMetricsFlag = metrics->fFontMetricsFlag ^FontMetrics::kUnderlinePositionIsValid_FontMetricsflag;
+        }
     }
     return metrics->fDescent - metrics->fAscent + metrics->fLeading;
 }
 
 ///////////////////////////////////////////////////////////////////////////////
 
 static void set_bounds(const SkGlyph& g, SkRect* bounds, SkScalar scale) {
     bounds->set(g.fLeft * scale,
                 g.fTop * scale,
                 (g.fLeft + g.fWidth) * scale,
@@ skipping 941 matching lines @@
         this->getMaskFilter()->computeFastBounds(*storage, storage);
     }
 
     if (this->getImageFilter()) {
         this->getImageFilter()->computeFastBounds(*storage, storage);
     }
 
     return *storage;
 }
 
+bool SkPaint::isFontMetricsFlagSet(FontMetrics * fObject, FontMetrics::FontMetricsFlags flag) const
+{
+    if(fObject != NULL) {
+        return SkToBool(fObject->fFontMetricsFlag & flag);
+    }
+    return false;
+}
+
 #ifdef SK_DEVELOPER
 void SkPaint::toString(SkString* str) const {
     str->append("<dl><dt>SkPaint:</dt><dd><dl>");
 
     SkTypeface* typeface = this->getTypeface();
     if (NULL != typeface) {
         SkDynamicMemoryWStream ostream;
         typeface->serialize(&ostream);
         SkAutoTUnref<SkData> data(ostream.copyToData());
 
@@ skipping 273 matching lines @@
             case SkXfermode::kPlus_Mode:
                 return 0 == this->getAlpha();
             case SkXfermode::kDst_Mode:
                 return true;
             default:
                 break;
         }
     }
     return false;
 }