What kind of changes do you want to do? The icons are generated programmatically in the CTabFolderRenderer classes; you can replace this class with the swt-tab-renderer property. The height of the tab can be set by the swt-tab-height property, though I think this is only supported by the E4 custom CTabRendering tab renderer, and not the stock tab renderer.
The properties and interpretations supported by the stock and custom E4 TA renderer is confusing. I've been writing up some documentation, but it's still not quite ready. Sorry.
Thanks for the reply Brian.
Basically all I need to do is change the background color from that standard grey to a gradient color.
I checked out the e4 contacts app from the Eclipse repository and it suffers the exact same problem. Everything else gets skinned, except for those boxes.
For the time being I managed to hide them but I'd rather skin them than get them out of the way completely. And even if I can hide those, I still get the ones in the Progress view that have the same grey color so that's not really a solution.
On top of that, the tabs like the ones in the editor suffer the same behavior. You can skin them but there's a small corner on the top left that doesn't get the background color and is still grey. I'm posting a screenshot of my views to show you the problem.
Do you think that with the custom tab render I can get away with it or is it just a loss of time going down that way?
Thanks to Brian I managed to solve this problem. The real problem is that I was applying the theme programmatically through the IThemeManager and, for some unknown reason, the correct CSS styles weren't applied.
I moved on to using the extension point and setting the cssTheme property to the id of my theme and it started working correctly.