Qt + WINAPI + direct painting

[pherthyl]

Why are you using WinAPI to paint? Is there a problem with QPainter?

[JovianGhost]

I got it working, finally!

Set Qt::WA_PaintOnScreen in the QWidget constructor. Reimplement QPaintDevice:aintEngine() to return a null pointer. Just like is written in documentation on Qt::WA_PaintOnScreen.

It should be working.

That's what I did at first, but it didn't work. After you said this I went back to check it out and noticed something: when overriding paintEngine() I forgot to put the trailing "const" in the declaration and definition, so instead of

QPaintEngine* paintEngine() const { return 0; }

QPaintEngine* paintEngine() const { return 0; }

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I had

QPaintEngine* paintEngine() { return 0; }

QPaintEngine* paintEngine() { return 0; }

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which of course did nothing. So thanks!

Why are you using WinAPI to paint? Is there a problem with QPainter?

To be honest, I never really considered QPainter. I was trying to do this as low-level as possible to reduce the overhead introduced by Qt's painting framework. But it looks like QPainter will do exactly what I need, thanks!

[aamer4yu]

But it looks like QPainter will do exactly what I need, thanks!

Thats how it is done in Qt.

To be honest, I never really considered QPainter. I was trying to do this as low-level as possible to reduce the overhead introduced by Qt's painting framework.

Then why use Qt... there will be some overhead still :P
juzz kidding.. theres always tradeoff between complexity of code and runtime. And Qt's paint framework is not that slow..also if you use QPainter, your code will be cross platform !

[JovianGhost]

Well I've been experimenting with QPainter and so far it's working very well!

[aamer4yu]

Well I've been experimenting with QPainter and so far it's working very well!

Good to know ... I guess you had underestimated Qt's performance :P