TreeView plus-minus icon size-Collection of common programming errors

In TreeView fontsize – Custom Draw or Owner Draw, I learned how to change the font size of the text in a TreeView control. Just using WM_SETFONT message.

But when I increase the font size, the plus-minus sign is not changed at the same time.

How can I set the plus-minus sign icon size at runtime, according to the item size (which is determined by the font size).

Here is the picture: