Fullscreen Scaling Oddities

[NeuralStunner]

64-bit (Hg/mingw64 build), Windows 7

My monitor's native resolution is 1280x1024. I have a dual-screen setup on a dedicated nVidia card. (I'm not sure how relevant that is - SDL seems to be doing borderless fullscreen.)

1280x1024 Fits the screen properly, but everything is over-stretched vertically. Forcing 4:3 makes no difference. This is how it comes out:

1280x960 Ingame looks almost exactly like x1024, though oddly the menu scaling changes to a too-tall ratio. Here's the expected letterbox view (a mockup taken from windowed mode):

1280x800 Looks fine, expands to 16:10 with 1:1.2 pixel ratio. (If I force 4:3 I can get 1:1 pixel ratio as well.)

640x480 The most odd, it's getting stretched to 1280x1024 as before, but with the scaling even more broken. Note the alternating thin/thick rows, especially; visible around the status bar:

[Braden Obrzut]

Finally getting around to measuring this. I fail to see anything wrong with the native 1280x1024 screen shot? The pixel ratio of the door is 1:1.2 as it should be. Only thing different between the first and second picture is accounting for the 5:4 ratio.