symbolic SVG *not* as an icon?

[Amy C <mathematical coffee gmail com>]

Hi all,

I've got a .svg file that I'm using as a background of a St.Button via:

.my-button {
    background: url('background.svg');
}

The SVG has some white bits in it. What I'd like is to be able to do:

.my-button:toggled {
    color: blue;
}

And when I apply the 'toggled' style to the button, I'd like the white
bit of the SVG to turn blue. Like symbolic icons in the status area.

How do I do this? I instantiate the button via:

button = new St.Button({ style_class: 'my-button'});

which applies the background image. However, using `color:blue;`
doesn't turn the white bit blue.
Do I need to:

- somehow modify the SVG to make it know which colour should be changed
- do something else on the code side to say "this is a symbolic SVG"
(do I set it as an icon or something instead of putting it in the CSS
background property? Wasn't there some problem on this list a while
ago with not being able to set symbolic icons that are local?)

If it helps, the SVG is close-window.svg (the close button on windows
in the overview), but I modified it in Inkscape to remove the 'X' (and
I am drawing the symbol in by setting my St.Button's label property).
The white border around it is what I want to change colour.

cheers!