Mastering Perl/Tk

Altering the Highlight Rectangle

The highlight rectangle is normally displayed with a thickness of 2 pixels.^[3] This can be changed using the -highlightthicknessoption:

-highlightthickness => amount

The amount specified is any valid screen distance. In Figure 4-38, the Exit Button on the right has a -highlightthickness of 10 and has the focus.

Figure 4-38. Example of -highlightthickness => 10

When the Button doesn’t have the keyboard focus, a small space is left around it. If this extra space bothers you, you can set -highlightthickness to 0 and the space won’t display, even if that widget has the focus. It is bad style to set the -highlightthickness to 0 without setting -takefocus to 0.

The color of the highlight rectangle can also be changed. There are two values for this: the color of the highlight rectangle when the Button does not have the focus and the color of the highlight rectangle when it does have the focus. The option -highlightcolor is the color of the highlight rectangle when the Button does have focus:

-highlightcolor => color

Figure 4-39 shows the right Button with the focus and with -highlightcolor set to 'yellow'. Compare it to Figure 4-38 to see the difference.

Figure 4-39. Example of Button with -highlightcolor => `yellow’

To change the color of the space left around ...