As there don’t seem to be any documentation about that, I don’t really know how to do it.
I heard that UE4 is using the SDL (Is that true on Linux, windows, and mac os ?).
Is it possible to access the SDL directly to draw in the window ?
Is there a better way to do this ?
UE4 has 2 UI systems that can be used to draw on screen, one is old HUD system which been around in UE3 maybe even ealier, it works more like HTML5 canvas. Asside of that there is also Slate, which is UI system made for editor, but it can be used in game, UMG (Widget Blueprints) is powered by. UMG was made because Slate is not implemented inside UE4 reflection system and it’s needed in order to be usable in blueprint.
Slate is widget based, but you can code how widget is drawn on OnPaint event, by giving intructions to slate renderer
there not much documentation on Slate so you will need to look up existing code to figure things out