Wintab: my application conflict with other tablet-aware applications

Why does my application sometimes not receive tablet data if another tablet-aw开发者_JAVA百科are (Wintab) application is running?

I read somewhere that Wintab contexts are stacked upon one another and only the topmost context in the overlap order receives tablet data.

but how to stack up to be topmost context?

Nevermind, I find the answer...

When an application becomes the active application, it should move its context to the top of the overlap order by calling WTOverlap( hWintabContext, TRUE ). When an application becomes inactive, it should call WTOverlap( hWintabContext, FALSE) to move its context to the bottom of the overlap order. The RULE2 example in the Wintab SDK shows how to appropriately handle context overlap order as a result of a WM_ACTIVATE message.