How can backends properly support Context::set_zoom_factor?

[dgulotta]

The Context::set_zoom_factor function works properly in eframe, but it seems to be broken in a lot of other backends (bevy, notan, sdl2_gl are the ones I tried). I wanted to try to fix one of these, but I'm not sure where to start. Is there any place that I should look to understand what eframe does to make zoom factors work?

[dgulotta]

I looked at the egui_glow code and it seems that:

• raw_input.screen_rect needs to be divided by the zoom factor.
• The renderer needs to scale the egui output by the zoom factor.