Cocoa Programming for OS X: The Big Nerd Ranch Guide

Views, Rectangles, and Coordinate Systems

When a window appears on screen, Cocoa must position each view in the window’s hierarchy. To know how to position a view, Cocoa needs two pieces of information:

• the origin, or position of the lower-left corner of the view in relation to the lower-left corner of its superview

• the size of the rectangle occupied by the view

frame

The position and size of the view are specified by its frame property, which is an NSRect.

  struct NSRect {
      var origin: NSPoint
      var size: NSSize
  }

The origin of the frame specifies the position of the lower-left corner as the offset from the superview’s lower-left corner. It is a coordinate in 2D space, represented by an NSPoint with x and ...