One thing that is giving me trouble is getting selected cells in NSTableView and NSBrowser to have a highlighted text color.
For tables, I've found the relevant place in GSThemeDrawing.m; it's -drawTableViewRow:clipRect:inView:, and I have access to the NSCell and know whether the table cell should be selected. My problem is, I don't know how I should I set up the cell. Simply calling -setHighlighted: YES doesn't cause a NSTextFieldCell to draw differently than normal.
I could explicitly set the text color to a highlighted text color in -drawTableViewRow:clipRect:inView:, but this would break cells that have custom text colors already set, which seems like a bad thing.