Letterboxing or Pillarboxing along with some stretching logic occurs if `Maintain Aspect Ratio` is selected.It should only be disabled to increase performance (since it's accomplished with two scaling passes) Auto-Prescaling happens here if bilinear or bicubic is selected-this will result in a less blurry result for large scale factors, so it should almost always be desireable.Final filter is applied to get the game up to the window size.This is a little unusual, and while it's useful sometimes to view a filter as literally mutating the console's output, there are more senses in which this prescaling concept is useful. Prescale does not affect the View > Window Size (1x, 2x, etc.) logic, it is best viewed as strictly an assist to the subsequent scaling+filtering steps. This comes after the prior steps because the lua-related stuff needs to get scaled precisely along with the game content. The main use of this is to reduce the overall blurriness of highly scaled Final Filtered results. This simply multiplies the game's display area. Imagine tacking on a sidebar to the side of the game This is used for displaying debug data on the `emu` surface while running lua scripts on. You can't see this in the Display Configuration, but it can be enabled through Lua. `Game Extra Padding` is added as blackness.

I'm not sure I like this sometimes, I think it should optionally move to before Prescale. The main display process works generally as follows:

Retroarch pcsx fullscreen