Bug 1478574 - Fix off-by-one error in marking explicit hyphens, so we don't introduce spurious pre-hyphen breaks. r=dbaron

layout/generic/nsTextFrame.cpp

@@ -3643,7 +3643,9 @@ PropertyProvider::GetHyphenationBreaks(Range aRange, HyphenType* aBreakBefore) c
     uint32_t currentFragOffset = mStart.GetOriginalOffset();
     for (uint32_t i = 0; i < aRange.Length(); ++i) {
       if (IS_HYPHEN(mFrag->CharAt(currentFragOffset + i))) {
-        aBreakBefore[i] = HyphenType::Explicit;
+        if (i < aRange.Length() - 1) {
+          aBreakBefore[i + 1] = HyphenType::Explicit;
+        }
         continue;
       }
 

layout/reftests/text/reftest.list

@@ -321,7 +321,7 @@ pref(gfx.font_rendering.graphite.enabled,true) == glyph-decomposition-graphite.h
 == hyphenation-control-2.html hyphenation-control-2-ref.html
 == hyphenation-control-3.html hyphenation-control-3-ref.html
 == hyphenation-control-4.html hyphenation-control-4-ref.html
-fails == hyphenation-control-5.html hyphenation-control-5-ref.html # bug 1478574
+fuzzy-if(winWidget,47,6) == hyphenation-control-5.html hyphenation-control-5-ref.html
 
 # osx-font-smoothing - with and without subpixel AA, only under OSX
 fails-if(!cocoaWidget) != osx-font-smoothing.html osx-font-smoothing-ref.html