I've just noticed that buttons overlapping tab panels behave differently depending on the position and state of the tabs. The button is not contained by the tab panel. It is deliberately placed outside the bounds of the tab panel so that it can be stacked above all the tabs.
When a button is overlapping a tab panel and placed above it in the stack order and the mouse is clicked in a location that falls within a tab the mouse-click is directed to the tab and trapped. The result is that the tab contents are displayed. The button doesn't recieve the mouse-click. If the tab is the active tab then the mouse-click is passed through to the button.
I expect a button overlaying another element to trap the mouse-click.
Has anyone met this problem and found a solution?