[SCM] WebKit Debian packaging branch, debian/experimental, updated. upstream/1.3.3-9427-gc2be6fc

[mitz at apple.com]

The following commit has been merged in the debian/experimental branch:
commit 78a6a0e757cdf8260a4b3f40749279e089974e20
Author: mitz at apple.com <mitz at apple.com@268f45cc-cd09-0410-ab3c-d52691b4dbfc>
Date:   Thu Sep 23 16:18:01 2010 +0000

    Address a remaining discrepancy in piecewise text measurement
    https://bugs.webkit.org/show_bug.cgi?id=45796
    
    Patch by Brad Moore <bradm at apple.com> on 2010-09-23
    Reviewed by Dan Bernstein.
    
    Don't include always-integral space widths in the floating point accumulator designed
    to minimize precision loss.  This brings whole-string measurement in line with piecewise
    text measurement when dealing with fonts with fractional advances.
    
    * platform/graphics/WidthIterator.cpp:
    (WebCore::WidthIterator::advance): Change the associativity of width addition to minimize precision loss.
    
    
    
    git-svn-id: http://svn.webkit.org/repository/webkit/trunk@68148 268f45cc-cd09-0410-ab3c-d52691b4dbfc

diff --git a/WebCore/ChangeLog b/WebCore/ChangeLog
index a181bd9..64f9682 100644
--- a/WebCore/ChangeLog
+++ b/WebCore/ChangeLog
@@ -1,3 +1,17 @@
+2010-09-23  Brad Moore  <bradm at apple.com>
+
+        Reviewed by Dan Bernstein.
+
+        Address a remaining discrepancy in piecewise text measurement
+        https://bugs.webkit.org/show_bug.cgi?id=45796
+
+        Don't include always-integral space widths in the floating point accumulator designed
+        to minimize precision loss.  This brings whole-string measurement in line with piecewise
+        text measurement when dealing with fonts with fractional advances.
+
+        * platform/graphics/WidthIterator.cpp:
+        (WebCore::WidthIterator::advance): Change the associativity of width addition to minimize precision loss.
+
 2010-09-23  Patrick Gansterer  <paroga at webkit.org>
 
         Reviewed by Adam Roben.
diff --git a/WebCore/platform/graphics/WidthIterator.cpp b/WebCore/platform/graphics/WidthIterator.cpp
index ef047e8..ae58918 100644
--- a/WebCore/platform/graphics/WidthIterator.cpp
+++ b/WebCore/platform/graphics/WidthIterator.cpp
@@ -212,20 +212,29 @@ void WidthIterator::advance(int offset, GlyphBuffer* glyphBuffer)
 
         // Force characters that are used to determine word boundaries for the rounding hack
         // to be integer width, so following words will start on an integer boundary.
-        if (m_run.applyWordRounding() && Font::isRoundingHackCharacter(c))
+        if (m_run.applyWordRounding() && Font::isRoundingHackCharacter(c)) {
             width = ceilf(width);
 
-        // Check to see if the next character is a "rounding hack character", if so, adjust
-        // width so that the total run width will be on an integer boundary.
-        if ((m_run.applyWordRounding() && currentCharacter < m_run.length() && Font::isRoundingHackCharacter(*cp))
-                || (m_run.applyRunRounding() && currentCharacter >= m_end)) {
-            float totalWidth = widthSinceLastRounding + width;
-            widthSinceLastRounding = ceilf(totalWidth);
-            width += widthSinceLastRounding - totalWidth;
-            m_runWidthSoFar += widthSinceLastRounding;
-            widthSinceLastRounding = 0;
-        } else
-            widthSinceLastRounding += width;
+            // Since widthSinceLastRounding can lose precision if we include measurements for
+            // preceding whitespace, we bypass it here.
+            m_runWidthSoFar += width;
+
+            // Since this is a rounding hack character, we should have reset this sum on the previous
+            // iteration.
+            ASSERT(!widthSinceLastRounding);
+        } else {
+            // Check to see if the next character is a "rounding hack character", if so, adjust
+            // width so that the total run width will be on an integer boundary.
+            if ((m_run.applyWordRounding() && currentCharacter < m_run.length() && Font::isRoundingHackCharacter(*cp))
+                    || (m_run.applyRunRounding() && currentCharacter >= m_end)) {
+                float totalWidth = widthSinceLastRounding + width;
+                widthSinceLastRounding = ceilf(totalWidth);
+                width += widthSinceLastRounding - totalWidth;
+                m_runWidthSoFar += widthSinceLastRounding;
+                widthSinceLastRounding = 0;
+            } else
+                widthSinceLastRounding += width;
+        }
 
         if (glyphBuffer)
             glyphBuffer->add(glyph, fontData, (rtl ? oldWidth + lastRoundingWidth : width));

-- 
WebKit Debian packaging