Game Programming Using Qt Beginner's Guide

Time for action – making the diagram more colorful

The diagram serves its purpose, but it looks a bit dull. Add some shine to it by defining three new color properties in the canvas object–color, topColor, bottomColor–and setting their default values to black, red, and blue, respectively.

Since points and arg should not really be public properties that anyone can change behind our backs, we'll correct it now. Declare a child element of the canvas of QtObject and set its ID to priv. Move declarations of points and arg inside that object. Move the onArgChanged handler there, as well:

QtObject { id: priv property var points: [] property real arg: -Math.PI onArgChanged: { points.push(func(arg)) points = points.slice(-canvas.width) canvas.requestPaint() ...