Part of the fix required adding logic to SynthProgressBarUI for dealing with tiles, and using those tiles to paint the indeterminate state. This was pretty straightforward. The difficult part was that in Nimbus we specify different "padding" based on whether the bar is determinate or indeterminate. SynthProgressBarUI doesn't really support this, unless you return a different SynthStyle instance. I removed an if check to cause the style to be reread anyway, even if it is the "same" as the previous style. I also changed the property change notification handler to update the style if the indeterminate progress changes.