I've just upgraded to Qt 4.5 RC1 (same system with ATI proprietary drivers). The problem is almost solved by the new Qt.
To see the slowdown, you now need to have a long line with more than 15000 characters.
When launched as "kwrite --graphicssystem raster", slowdown disappears completely and kwrite from KDE4 behaves just like kwrite from KDE3.
I've just upgraded to Qt 4.5 RC1 (same system with ATI proprietary drivers). The problem is almost solved by the new Qt.
To see the slowdown, you now need to have a long line with more than 15000 characters.
When launched as "kwrite --graphicssystem raster", slowdown disappears completely and kwrite from KDE4 behaves just like kwrite from KDE3.