In Options->Debug->Redrawing you can enable Print redraw time to terminal. With this you can debug both how often the screen actually redraws and how long each redraw takes.

Yep, rotation in its current unaccelerated form is unfortunately quite resource-expensive. Also modRana always redraws the complete viewport (with the exception of the simple manual map dragging method) which probably further slows down the VNC viewer that might be trying to only transfer areas that have changed, which won't work as the whole screen changes.

Also by default, when a new tile is loaded, the screen is redrawn - this might be an issue when moving too fast, eq. many new tiles are loaded all the time. this behavior can be disabled in Options->Debug->Tiles->Redraw screen once a new tile is loaded. Might help to reduce the number of redraws quite a bit.

There is also another trick used to reduce the are that needs to be redrawn:
Just update the area around the position indicator and redraw the whole screen only once it gets too close to the edge (TangoGPS works like this). This is not yet implemented in modRana.

Yes, this is still a possibility - the location info reading thread wakes up every time GPSD has a position update. If it is feeding too many updates, the thread might be running too often, hogging resources.
You can debug this by enabling Show GPSD debug output in
Options->Debug->GPS and checking how often the a new fix is reported.

The whole GUI is drawn with Cairo - would have to check out if it can do this (probably can). Still might end up to be more resource intensive than no filter.

Yes, but I'd rather first make sure this is what's really causing it as using GPSD simplifies quite a few things. Would bet its rather the frequent fullscreen redraws swamping the VNC viewer.


If Options->Debug->Tiles->Redraw screen once a new tile is loaded is disabled, the screen should actually update just about once a second. But it might be a good idea to add an option that forces a fixed global redraw interval.