Hi,

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Thats correct, however you can paint to a context without invalidating a region. Consider this, you have a hot tracking effect in your client area - you want the fastest mechanism for updating a tiny portion of the display avoiding overdraw, flickering etc. Do you invalidate a region and give windows its dirty rectangle (slow) or do you draw the effect directly to the controls display context (quick) and pay the price of not supporting standard behaviour by re-creating the tooltip (or any potential window of this class)?
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So you're suggesting drawing to the 'lower' device context and then re-creating the tooltip (or any potential window of this class)? I'd be surprised if that was faster than invalidating it. Also it seems like dangerous behaviour in the sandbox - how do you know that other windows won't be written onto by your draw?

Regards,
Viv