Issue 923: Antialiasing artifact fix
Issue 923: Antialiasing artifact fix

The API for QPainter::renderHints() does not work as we expected.

QPainter::setRenderHints clears or sets all flags present. It does not
set the aggregate value.

We need to manually set/clear the Antialiasing flag.

equalsraf/neovim-qt,equalsraf/neovim-qt,equalsraf/neovim-qt,equalsraf/neovim-qt