Bar Theming API

This is the first approach to replace the current theming API.

Goals

• Provide backwards compatibility.
• Don't need to access object members like parents or other stuff.
• Avoid the need to know implementation details of widgets to write engines.
• Improve support for dynamic style properties.
• Provide an extensible context information provider from widgets (kill the detail string!)

Proposal: GtkStyleContext

• A new GtkStyleContext object that can contain multiple values/hints. This would substitute the detail string, and would allow less scary if switches within the engines implementation.

• Each GtkStyleContext should have an unique id, such as GtkComboBox.Button, for a button in a combobox. This naming should have some sort of consistency.

Backwards compatibility

• Reimplement a compatibility layer for legacy primitives. This legacy implementation would call the new primitives by creating a new GtkStyleContext that would fit the current call+detail string. It's pretty much like emulating what a current engine does, but instead of painting, calling the new primitives.