Comment 30 for bug 1797308

@Seth, yeah it's not a complete patch, it also makes the grid very heavy. The patch is more to say it is possible to compensate for the DPI stuff, but just not automatically.

It does work OK if you also set GDK_SCALE=2 (as then GDK is scaling the mouse events in the opposite direction, I suppose...) to simulate a (small) hi-DPI screen.

So the question is how much care do we need to take when the user has set a scale that doesn't agree with the toolkit's scaling? When you get the factor from the toolkit, you can't have a discrepancy, but when the users can set it manually, lots of things can get out of sync, because the canvas is at a totally different scale to the input event co-ordinates.

Cairo is not changed by this config, but it could hook into the same values if we know what to do with them (cairo_scale or a surface scale factor?)