I have implemented Map zoom by pinch gesture from touch-screen and Pinch gesture zoom uses digital scaling appropriate for maps. and prepared pull request. But author reply is not promising that it would be integrated into mainline soon. So you can use my branch zoom-by-pinch from my fork for now. If there is interest I provide binaries or Debian package. I am not sure if proposal of GPXsee to become PureOS package worth if mainline is reasonably usable only on machines with mouse wheel and keyborad and enhancement for convertibles and mobile phones is considered unacceptable for now.