GTKD - overrideBackgroundColor of Button doesn't work

[captaindet via Digitalmars-d-learn]

>          string cssPath = "test.css";
>
>          CssProvider provider = new CssProvider();
>          provider.loadFromPath(cssPath);

unfortunately i don't know anything about yr specific problem.

but i just wanted to mention (in case you are not aware of it) that the 
CSS can be embedded into the D source. this is what i did to fix GTKs 
terrible design mistake for the background of Notebook:

```
enum myCSS = q{
     GtkNotebook {
         background-color: #e9e9e9;
     }
     GtkNotebook tab {
         background-color: #d6d6d6;
     }
};
...
int main(string[] args){
...
     import gtk.CssProvider;
     auto styleProvider = new CssProvider;
     styleProvider.loadFromData(myCSS);
     import gdk.Screen;
     import gtk.StyleContext;
     StyleContext.addProviderForScreen( Screen.getDefault(), 
styleProvider, 800);
```