In order to get smooth scrolling in DOSBox-SVN, I need to enable the “refresh rate switching” option. This works great with g-sync. Scrolling becomes perfect without any frame skips.
However, there is a tear line. It’s perfectly fixed in position and doesn’t move up or down, not even by a single pixel. This seems to be the internal vsync emulation of DOSBox picking the wrong scanline to sync against. This scanline changes when quitting and reloading the core, so the tear line will appear at a different position between runs.
Note that this tear line is drawn by dosbox. This is not tearing that happens at the host machine level where RetroArch is running. It’s the internal vsync emulation of dosbox that draws the tearing. Pausing dosbox during a scroll for example will also pause the tear line and keep it visible.
If I restart the core enough times, I can get that tear line to be hidden below the bottom edge of the image. Since the tear position is fixed, it stays there forever (until the next time the core is restarted.) However, it takes many attempts and as a result becomes very annoying.
Does anybody else experience this?