Created attachment 179260 [details] Patch for qtwebkit 2.3 Offset computation in offsetForPositionForSimpleText is not correct in Source/WebCore/platform/graphics/qt/FontQt4.cpp implementation whereas the equivalent offset computation used in Qt5 in Source/WebCore/platform/graphics/FontFastPath.cpp is correct. You can compare the result of webkit test LayoutTests/fast/css/text-overflow-ellipsis.html between Qt 4 and Qt 5 to stimulate this issue.
Landed in qtwebkit-2.3-staging by commit ec61316964f0d7088f9532c3edca9e468bf870c7