Fix of HighDPI rendering

In response to issue https://gitlab.vci.rwth-aachen.de:9000/OpenFlipper-Free/OpenFlipper/-/issues/28 I propose following fix:

• make glViewer aware of device pixel ratio and incorporate dpr into viewport size/offset calculation

Below is a recording of the fix running on my machine. DPR scaling set to 2 and 1 to demonstrate no breaking changes for regular screens.

Todo: Requires verification on high-dpi screens

(double click for full resolution)

fix