Cocoa Programming for OS X: The Big Nerd Ranch Guide

For the More Curious: Rollovers

Three mouse event methods were not discussed in Chapter 18: mouseMoved(_:), mouseEntered(_:), and mouseExited(_:).

To receive mouseMoved(_:), the view’s window needs to accept mouse moved events. If it does, the mouseMoved(_:) message is sent to the window’s first responder. To set the window to get mouse moved events, set the acceptsMouseMovedEvents property to true:

w​i​n​d​o​w​?​.​a​c​c​e​p​t​s​M​o​u​s​e​M​o​v​e​d​E​v​e​n​t​s​ ​=​ ​t​r​u​e​

At this point, the view will be sent the message every time the mouse moves. This is a lot of events. When people ask about mouse moved events, we ask them why they want it. They usually say, “Uh, rollovers.”

Rollovers are very popular with hyperlinks. As ...