Linux: Match the tmMaxCharWidth of Windows exactly.

The metric used is totally wrong, it's much larger than the largest advance of
any glyph in the font. However, it's wrong in exactly the same way as Windows
is.

Review URL: http://codereview.chromium.org/12505


git-svn-id: svn://svn.chromium.org/chrome/trunk/src@6073 0039d316-1c4b-4281-b951-d872f2087c98

4 files changed, 10 insertions, 4 deletions

diff --git a/skia/include/SkPaint.h b/skia/include/SkPaint.h
index 921245b..9529dd0 100644
--- a/skia/include/SkPaint.h
+++ b/skia/include/SkPaint.h
@@ -588,6 +588,10 @@ public:
         SkScalar    fLeading;   //!< The recommended distance to add between lines of text (will be >= 0)
         SkScalar    fHeight;    //!< the vertical distance between two consecutive baselines (>= 0)
         SkScalar    fAvgCharWidth;  //!< the average charactor width (>= 0)
+        SkScalar    fXRange;        //!< This is the maximum range of X bounding box points
+                                    //   in units of em. It's used to calculate a value which
+                                    //   matches Windows's GetTextMetrics tmMaxCharWidth
+                                    //   member exactly.
 
         // VDMX values are exact ascent and descent values for scalable fonts at
         // a certain pixel size.
diff --git a/skia/ports/SkFontHost_FreeType.cpp b/skia/ports/SkFontHost_FreeType.cpp
index 3011811..46c86b6 100644
--- a/skia/ports/SkFontHost_FreeType.cpp
+++ b/skia/ports/SkFontHost_FreeType.cpp
@@ -792,6 +792,7 @@ void SkScalerContext_FreeType::generateFontMetrics(SkPaint::FontMetrics* mx, SkP
     SkFixed scaleY = fScaleY;
     SkFixed mxy = fMatrix22.xy;
     SkFixed myy = fMatrix22.yy;
+    SkScalar xrange = static_cast<SkScalar>(face->bbox.xMax - face->bbox.xMin) / upem;
 
     int leading = face->height - face->ascender + face->descender;
     if (leading < 0)
@@ -817,7 +818,7 @@ void SkScalerContext_FreeType::generateFontMetrics(SkPaint::FontMetrics* mx, SkP
         y = SkFixedMul(myy, y);
         pts[i].set(SkFixedToScalar(x), SkFixedToScalar(y));
     }
-    
+
     if (mx)
     {
         mx->fTop = pts[0].fX;
@@ -827,6 +828,7 @@ void SkScalerContext_FreeType::generateFontMetrics(SkPaint::FontMetrics* mx, SkP
         mx->fLeading = pts[4].fX;
         mx->fHeight = pts[5].fX;
         mx->fAvgCharWidth = pts[6].fX;
+        mx->fXRange = xrange;
 
         // The VDMX metrics only make sense in the horizontal direction
         // I believe
@@ -841,6 +843,7 @@ void SkScalerContext_FreeType::generateFontMetrics(SkPaint::FontMetrics* mx, SkP
         my->fLeading = pts[4].fY;
         my->fHeight = pts[5].fY;
         my->fAvgCharWidth = pts[6].fY;
+        my->fXRange = xrange;
         my->fVDMXMetricsValid = false;
 
         // Attempt to parse the VDMX table to get exact metrics
diff --git a/webkit/port/platform/graphics/chromium/FontCacheLinux.cpp b/webkit/port/platform/graphics/chromium/FontCacheLinux.cpp
index ab37374..b9aa718 100644
--- a/webkit/port/platform/graphics/chromium/FontCacheLinux.cpp
+++ b/webkit/port/platform/graphics/chromium/FontCacheLinux.cpp
@@ -96,7 +96,7 @@ FontPlatformData* FontCache::createFontPlatformData(const FontDescription& fontD
         style |= SkTypeface::kItalic;
 
     SkTypeface* tf = SkTypeface::Create(name, (SkTypeface::Style)style);
-    
+
     FontPlatformData* result =
         new FontPlatformData(tf,
                              fontDescription.computedSize(),
diff --git a/webkit/port/platform/graphics/chromium/SimpleFontDataLinux.cpp b/webkit/port/platform/graphics/chromium/SimpleFontDataLinux.cpp
index 7b8a75e..c5080c9 100644
--- a/webkit/port/platform/graphics/chromium/SimpleFontDataLinux.cpp
+++ b/webkit/port/platform/graphics/chromium/SimpleFontDataLinux.cpp
@@ -52,8 +52,7 @@ void SimpleFontData::platformInit()
     if (!glyphPageZero)
       return;
 
-    static const UChar32 M_char = 'M';
-    m_maxCharWidth = widthForGlyph(glyphPageZero->glyphDataForCharacter(M_char).glyph);
+    m_maxCharWidth = SkScalarRound(metrics.fXRange * SkScalarRound(m_font.size()));
 
     if (metrics.fAvgCharWidth) {
         m_avgCharWidth = SkScalarRound(metrics.fAvgCharWidth);