Apply screen DPI scaling and expose logical coordinates instead of physical (?)

[hecrj]

As of now, Coffee converts logical coordinates into physical coordinates (examples here and here) for everything.

However, the winit::dpi documentation seems to hint that we should instead expose logical coordinates everywhere and apply a scaling transformation when rendering on screen. This can be easily implemented by making Frame apply a scaling transformation using Target::with_transform in the as_target method here.

This would have the benefit that games will look similar in size in different devices. However, targeting specific pixels when rendering becomes harder. Can this cause graphical glitches? Maybe Window could expose the dpi value so developers can undo the dpi scaling if they deem necessary? What about a different type, like Frame but that does not apply a DPI transformation when seen as a Target?