Why do the corner points of a rectangle have odd coordinates?

[Sano]

Hello, I noticed some small bug in my code which led me to the following oddity.

QRect b(0,0,100,100)
int c = b.topRight().x()

Why is c = 99 and not 100? This doesn't make any sense for me.

[Christian Ehrlicher]

@Sano said in Why do the corner points of a rectangle have odd coordinates?:

Why is c = 99 and not 100?

Because it's made for displaying rects on the screen - see also https://lists.qt-project.org/pipermail/development/2022-April/042379.html

[ChrisW67]

QRect b(0,0,100,100); // a rectangle at (0,0) that is 100 by 100 units in size.

In your rectangle:

• There are 100 columns from left-to-right numbered from 0 to 99.
• There are 100 rows from top-to-bottom numbered from 0 to 99.