Game Programming Using Qt Beginner's Guide

Time for action – making oscillograms selectable

It's time to make our oscillogram widget interactive. We will teach it to add a couple of lines of code to it that let the user select part of the plot. Let's start with storage for the selection. We'll need two integer variables that can be accessed via read-only properties; therefore, add the following two properties to the class (you can initialize them both to -1) and implement their getters:

Q_PROPERTY(int selectionStart READ selectionStart NOTIFY selectionChanged)
Q_PROPERTY(int selectionEnd READ selectionEnd NOTIFY selectionChanged)

The user can change the selection by dragging the mouse cursor over the plot. When the user presses the mouse button over some place in the plot, we'll mark that ...