Does anyone know the reasoning for Right and Bottom?

I have a Canvas that’s 100X100 and the last pixel in the canvas will be #99 as 0 is counted as the 1st.
Now I make a REALBasic.Rect (0, 0. 100, 100)
I would assume the Width and Height would be 100 (which it is), but I would also assume the Right and Bottom to be 99 (which it isn’t).

If I want to draw a line that is stops at the edge of the Realbasic.Rect I need to subtract 1 from the right. I don’t understand why it Right doesn’t use the last contained pixel.

This sounds like old MacOS rules where the coordinates were theoretical mathematical points that laid in between the actual pixels. So the coordinate (0,100) would surround pixels from (0,0 to 0,99) but not (0,100). I think this has been interpreted differently by many OSs and has lead to many OBOEs.

I think both ways are valid approaches, but the main question here is whether it’s consistent from OS to OS?

Or, it could just be a bug: I found an OBOE here : <>