Overlay

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Originally Posted by ToddAtWSU

I am not sure why putting the * in front helps.

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It helps because you are now giving it the argument type that it is expecting rather than the argument type that it is not expecting.

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To me that turns the pointer into a pointer to a pointer

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No, that de-references the pointer. See any docs on C/C++ to see the meaning of the '*' operator.

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I thought the function wanted my argument de-referenced, but I guess not.

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The function wants a reference to a QPixmap object, nothing more. Whether that means de-referencing your variable depends on what kind of object you are dealing with, a QPixmap or a 'pointer to QPixmap'. The following should show you how to correctly deal with both cases.

Example 1 - QPixmap allocated on the stack.

Code:

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mOverlay = QPixmap( 561, 351 );
 ...
mpVideoPainter->drawPixmap( target, mOverlay, source );

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Example 2 - QPixmap allocated on the heap.

Code:

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mpOverlay = new QPixmap( 561, 351 );
 ...
mpVideoPainter->drawPixmap( target, *mpOverlay, source );

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I don't know what I was thinking, must have been having a brain freeze at that point. I have been working with C/C++ for 4+ years now, but for some reason I was thinking the & and the * were backwards when I was working on that. Probably too much programming and not enough sunlight.