Correcting text baseline for tiny fonts

third_party/WebKit/Source/modules/canvas2d/CanvasRenderingContext2D.cpp

 /*
  * Copyright (C) 2004, 2005, 2006, 2007, 2008, 2009, 2010, 2011, 2012 Apple Inc.
  * All rights reserved.
  * Copyright (C) 2008, 2010 Nokia Corporation and/or its subsidiary(-ies)
  * Copyright (C) 2007 Alp Toker <alp@atoker.com>
  * Copyright (C) 2008 Eric Seidel <eric@webkit.org>
  * Copyright (C) 2008 Dirk Schulze <krit@webkit.org>
  * Copyright (C) 2010 Torch Mobile (Beijing) Co. Ltd. All rights reserved.
  * Copyright (C) 2012, 2013 Intel Corporation. All rights reserved.
  * Copyright (C) 2013 Adobe Systems Incorporated. All rights reserved.
@@ skipping 738 matching lines @@
     direction = toTextDirection(state().getDirection(), canvas());
   TextRun textRun(text, 0, 0, TextRun::AllowTrailingExpansion |
                                   TextRun::ForbidLeadingExpansion,
                   direction, false);
   textRun.setNormalizeSpace(true);
   FloatRect textBounds = font.selectionRectForText(
       textRun, FloatPoint(), font.getFontDescription().computedSize(), 0, -1,
       true);
 
   // x direction
-  metrics->setWidth(font.width(textRun));
-  metrics->setActualBoundingBoxLeft(-textBounds.x());
-  metrics->setActualBoundingBoxRight(textBounds.maxX());
+  metrics->setWidth(SkScalarRoundToInt(font.width(textRun)));
+  metrics->setActualBoundingBoxLeft(SkScalarRoundToInt(-textBounds.x()));
+  metrics->setActualBoundingBoxRight(SkScalarRoundToInt(textBounds.maxX()));
 
   // y direction
   const FontMetrics& fontMetrics = font.getFontMetrics();
-  const float ascent = fontMetrics.floatAscent();
-  const float descent = fontMetrics.floatDescent();
-  const float baselineY = getFontBaseline(fontMetrics);
+  const float ascent = fontMetrics.ascent();
+  const float descent = fontMetrics.descent();
+  const float baselineY = SkScalarRoundToInt(getFontBaseline(fontMetrics));
 
   metrics->setFontBoundingBoxAscent(ascent - baselineY);
   metrics->setFontBoundingBoxDescent(descent + baselineY);
-  metrics->setActualBoundingBoxAscent(-textBounds.y() - baselineY);
-  metrics->setActualBoundingBoxDescent(textBounds.maxY() + baselineY);
+  metrics->setActualBoundingBoxAscent(SkScalarRoundToInt(-textBounds.y()) -
+                                      baselineY);
+  metrics->setActualBoundingBoxDescent(SkScalarRoundToInt(textBounds.maxY()) +
+                                       baselineY);
 
   // Note : top/bottom and ascend/descend are currently the same, so there's no
   // difference between the EM box's top and bottom and the font's ascend and
   // descend
   metrics->setEmHeightAscent(0);
   metrics->setEmHeightDescent(0);
 
   metrics->setHangingBaseline(0.8f * ascent - baselineY);
   metrics->setAlphabeticBaseline(-baselineY);
   metrics->setIdeographicBaseline(-descent - baselineY);
@@ skipping 75 matching lines @@
       break;
   }
 
   // The slop built in to this mask rect matches the heuristic used in
   // FontCGWin.cpp for GDI text.
   TextRunPaintInfo textRunPaintInfo(textRun);
   textRunPaintInfo.bounds =
       FloatRect(location.x() - fontMetrics.height() / 2,
                 location.y() - fontMetrics.ascent() - fontMetrics.lineGap(),
                 width + fontMetrics.height(), fontMetrics.lineSpacing());
+
   if (paintType == CanvasRenderingContext2DState::StrokePaintType)
     inflateStrokeRect(textRunPaintInfo.bounds);
 
   CanvasRenderingContext2DAutoRestoreSkCanvas stateRestorer(this);
   if (useMaxWidth) {
     drawingCanvas()->save();
     drawingCanvas()->translate(location.x(), location.y());
     // We draw when fontWidth is 0 so compositing operations (eg, a "copy" op)
     // still work.
     drawingCanvas()->scale((fontWidth > 0 ? (width / fontWidth) : 0), 1);
@@ skipping 13 matching lines @@
       textRunPaintInfo.bounds, paintType);
 }
 
 const Font& CanvasRenderingContext2D::accessFont() {
   if (!state().hasRealizedFont())
     setFont(state().unparsedFont());
   canvas()->document().canvasFontCache()->willUseCurrentFont();
   return state().font();
 }
 
-int CanvasRenderingContext2D::getFontBaseline(
+float CanvasRenderingContext2D::getFontBaseline(
     const FontMetrics& fontMetrics) const {
   switch (state().getTextBaseline()) {
     case TopTextBaseline:
-      return fontMetrics.ascent();
+      return fontMetrics.floatAscent();

[eae, 2016/10/04 20:43:11]

In CanvasRenderingContext2D::measureText you changed it from floatAscent to
ascent and here the opposite despite that fact that both (presumably) return the
float value now. We should be consistent and use the same everywhere and remove
the float version if the regular one has float precision.

[zakerinasab1, 2016/10/06 20:02:52]

Fixed.

     case HangingTextBaseline:
       // According to
       // http://wiki.apache.org/xmlgraphics-fop/LineLayout/AlignmentHandling
       // "FOP (Formatting Objects Processor) puts the hanging baseline at 80% of
       // the ascender height"
-      return (fontMetrics.ascent() * 4) / 5;
+      return (fontMetrics.floatAscent() * 4.0) / 5.0;
     case BottomTextBaseline:
     case IdeographicTextBaseline:
-      return -fontMetrics.descent();
+      return -fontMetrics.floatDescent();
     case MiddleTextBaseline:
-      return -fontMetrics.descent() + fontMetrics.height() / 2;
+      return -fontMetrics.floatDescent() + fontMetrics.height() / 2.0;
     case AlphabeticTextBaseline:
     default:
       // Do nothing.
       break;
   }
   return 0;
 }
 
 void CanvasRenderingContext2D::setIsHidden(bool hidden) {
   if (canvas()->hasImageBuffer())
@@ skipping 201 matching lines @@
   }
   return true;
 }
 
 void CanvasRenderingContext2D::resetUsageTracking() {
   UsageCounters newCounters;
   m_usageCounters = newCounters;
 }
 
 }  // namespace blink