Knowing which part of a Window is currently visible on the display

[Ganesh]

Dear Experts,
I have an application that has several graphical components on it.
The state of these components is decided by some data which is
available in some data store. The graphical components periodically go
to the data base to see if the data has changed and accordingly change
their display state. Now its wasteful for my application to update its
graphical state if a particular component is not being visible
(meaning that some other Window is hiding a part or full of my
applications Window). I am trying to figure out which part of my
applications Window is currently visible on my computers display. This
way, my components can decided if they have to update themselves or
not (they could sit idle if they are not visible or could periodically
update their state if they are visible).
Any idea on how I can check which region on my Window is
currently visible on the display? Thanks.

Regards,
Ganesh Okade
Sunlux Technologies Ltd.

 

[Peter Duniho]

[...]
Any idea on how I can check which region on my Window is
currently visible on the display? Thanks.

Well, you can find out when your control/form is actually drawn by
checking the ClipRectangle in the PaintEventArgs. You could also just
compare the screen location with the screen boundary.

But IMHO this is not something you want to do. While I understand the
concern of not being "wasteful", in practice these sorts of optimizations
can lead to poor performance when the optimization can't be used (e.g. the
whole window is on-screen). I've been down that road, as well as know of
others who have, and it usually doesn't work out.

If there's a problem with performance when part of the window is
off-screen, then there's a problem with performance when none of the
window is off-screen. Your effort will be better invested addressing
performance in a more general way so that performance is acceptable
regardless of where the window is.

Pete