Just noticed this PR seems to drop support for Qt versions prior to 5.11. Hopefully that doesn't cause any issues. eg for anyone compiling this on enterprise and long term support releases of OS's. smile

Don't worry, the version check was due to the use of QFontMetrics::horizontalAdvance(), which was introduced in 5.11. The new code is simpler on the Qt side now, because @hikmet517 has delegated the logic to QScintilla, and should compile on every Qt5 out there.