window not drawn at correct size

[wheybags]

nk_flags windowFlags = NK_WINDOW_TITLE | NK_WINDOW_NO_SCROLLBAR;

if (nk_begin(ctx, "asdf", nk_rect(10, 10, 100, 100), windowFlags))
{
}
nk_end(ctx);

^ The above code should produce a 100x100 box, but is actually producing a 101x101 box:

There seems to be some feathering around the edges, which produces the "border", even though I haven't specified NK_WINDOW_BORDER. As I understand it, this feathering shouldn't be there, as I am specifying exact pixel coordinates, and the box is axis-aligned.

Original screenshot:

[wheybags]

This is with the sdl_opengl3 demo backend btw. Just tried with the gdip demo backend too, and the square is still 101x101, but the colour is solid all the way to the edges

[vurtun]

Hmm. At least xlib seems correct which makes this whole thing more complicated.

Honestly I have not idea what this could be. Probably a big mess that turns into a Whac-A-Mole between platforms.

[alekseyt]

I'm pretty sure it's some sort of rounding error.

Note how border is messed up at the bottom-left corner (top-left corner had same effect). Code was:

nk_begin(ctx, "Demo", nk_rect(0, 0, 100, 100)

Demo was sdl_opengl2, background color was changed to (255, 0, 0).

I suspect xlib is somehow fixing rounding, for example by aligning positions to pixels, but OpenGL is interpolating pixel values instead. Apparently, in picture above, bottom border (horizontal) pixels are at x=0 or close to that, but left border (vertical) pixels probably a little bit shifted to the right. This is just my guess.