How to gainst the window draw itself again and again?

[c154387417]

A newbie to Qt. If any strange questions i've post, forgive me please.

When window's move/resize envents happen,
how can it only draw a dotted-rectangle instead,
but do not let the system draw the window again and again.
That's too slow.

Yes, on windows platform, i can do it like this:

SystemParametersInfo(SPI_SETDRAGFULLWINDOWS, 
                        FALSE, NULL, NULL);

SystemParametersInfo(SPI_SETDRAGFULLWINDOWS, 
                        FALSE, NULL, NULL);

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Okay, i mean i need Cross Platform Code here.
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THANK YOU SO MUCH!
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Excuse me, for my English....and, any Chinese Qter here?