Scrollpane rounded border

[DevCharly]

This is an attempt to bring rounded border to JScrollPane and all component that are usually placed into a scrollpane. E.g. JTextArea, JTextPane, JEditorPane, JList, JTree and JTable.

The problem is that there are multiple overlapping components involved:

• the JScrollPane, which has the border
• the JViewport, which has the view component as child (e.g. a JList)
• optional column and row headers
• optional corner components
• vertical and horizontal JScrollBars

They are painted in this order and using rounded border on scrollpane would look like this:

The viewport/list and the scrollbar simply paint over the rounded corners.
And there is no way to fix this for the viewport in the look and feel.
(maybe a custom scrollpane implementation, that paints its border and corners after its children, could work)

So the idea to solve this problem is to add some extra space at left and right sides between the border and the viewport/scrollbars:

That's better, but the scrollbar should be at the border:

We can hide the scrollbar track and make the thumb round to improve the look:

ScrollBar.track = @componentBackground
ScrollBar.thumbInsets = 2,2,2,2
ScrollBar.thumbArc = 999

If the vertical scrollbar is hidden, it looks like this:

With rounded selection (and smaller border arc than in previous screenshots) this looks really nice:

ScrollPane.arc = 12
List.selectionArc = 8

Here are some screenshot that shows the extra space, which was added for rounded border, in green:

Smaller border arc results in smaller extra space, larger arc gives larger extra space:

Possible improvements/ideas:

• make viewport wider if vertical scrollbar is visible to remove the gap between viewport and vertical scrollbar (see above screenshot)
• adapt vertical scrollbar painting to rounded border to allow full height vertical scrollbar
• allow specifying scrollpane border arc for component types (e.g. use rounded border for multi-line text components, but not for lists, tables and trees)

For testing you need to enable rounded border. E.g.:

ScrollPane.arc = 12

[DevCharly]

Last commit removes gap between viewport and vertical scrollbar (if possible).

Before:

After:

If the scrollpane has a column header (e.g. a JTableHeader when using JTable) and a upper-right corner component (red rectangle), then it is not possible to remove the gap:

[BrantLauro]

Very good work, can I already use that as a Snapshot or something like this?

[DevCharly]

Last commit adds possibility to specify scroll pane arc for multi-line text components, lists, tables and trees.

There are four new UI properties that have default value -1, which means that ScrollPane.arc is used.

ScrollPane.List.arc = -1
ScrollPane.Table.arc = -1
ScrollPane.TextComponent.arc = -1
ScrollPane.Tree.arc = -1

E.g. if you want rounded border only for multi-line text components, then simply use:

ScrollPane.arc = 0
ScrollPane.TextComponent.arc = 12