I'm working on a Thunderbird extension of mine, removedupes. Among other things, it includes a dialog for reviewing duplicate message sets and deleting them; and that dialog has a tree-table widget, formerly a XUL tree. (old) Screenshot:
These days, XUL is being (gradually?) phased out, but Thunderbird (and Firefox I suppose) still supports this important widget.
When I resize my dialog, the tree widget expands, with it, which is good; but the tree column widths do not expand, so that when widening the dialog window, one has to manually expand each of them to make use of the larger width, which is bad.
Now, I can set the flex attribute of the tree columns to a positive value - which makes them auto-expand, which is good; but if I do that, the user can no longer change their widths manually, which is bad...
So, my question: How can I arrange it so that the columns do auto-resize on dialog resize, but still allow the user manual control over (relative) column widths when while the dialog width is fixed?