1. JToolBar - Separator line is short when position left/right
This was fixed by adding a custom painter for toolbar separators. The problem is that our designer tool doesn't allow for tiled painting yet, so we needed a custom painter to do this.
2. JToolBar - Outline line is missing when place at the bottom/right
And the line is in the wrong place when positioned left. To fix this bug I had to add 4 custom states for JToolBar to dectect which side of the screen it is on, so that I could then render the border on the correct side of the toolbar.
3. Inserting Box.createHorizontalGlue() to JTollBar on Nimbus doesn't work
This is not strictly a bug, but an RFE. We decided to support this feature. JToolBar, by default, uses a BoxLayout as its layout manager. Synth uses a custom layout manager. In some ways we prefer the synth one (by default, it looks better). However, in many ways we'd like Nimbus to be a drop-in replacement for Metal.
In this case we decided that since by default it looks hideous in Metal, that we'd rather that new apps by default look good in Nimbus. Therefore, we compromised. While we are not going to make the Synth layout manager the same as that used in Metal and the other LAFs, we are going to support "glue" created via Box.createHorizontalGlue(). This support was added directly to the Synth layout manager for toolbars.
4. Spinner & Editable JCombobox touches the border of the JToolbar
Simply added some insets to the toolbar. I had to mess with a few fiddly bits in NimbusIcon to get the icon to paint properly with the insets and border, but it should all now paint properly and look decent.