As I am quite used to screen geometry, where 0,0 is at the top left corner or the screen (as it is for just about every desktop app and Web app in the world), but I find it very hard to actually implement a UI in OpenGL since it's coordinate system is vertically inverted from what I have always worked with.
I'm trying to implement a GUI for a plugin for the game Rising World, and this is driving me crazy.
The added restriction that I have is that I do not have access to the actual screen resolution, but can only achieve full screen width and height using relative positioning and size (from 0 to 1). Sure, I can use pixels to position shapes and controls, but I cannot say, for example : place this at 50% - 20 pixels; it is either one or the other per shape.
I am Googling for things I can read about UI design with "inverted" Y coordinates (i.e. since we read from top to bottom, it is inverted to me), but I can't find anything relevant. And since I cannot use any third party GUI library but what the game is offering, I am restricted to basic shapes and positioning (i.e. doing things 100% manually).
Is there a way in this context that I can author my UI in a coordinate system where the origin is the top-left?