[Interest] Issue painting over child widgets

[Bill Crocker]

Murphy, Sean M. wrote:
> Ok, so how do I go about step #1 correctly?  My current application has one top-level layout, with all my widgets inside the layout.  Ideally, I'd like to have my application be resizable: allowing the QLayout to take care of my visible widgets.  So how do I get the invisible widget you're proposing to overlay the "real" widgets, as the application resizes?
>

Something like:

Create the overlay widget as an independent child of the top level widget (not the widgets layout).
Raise it to the top of the stack.
Manually move() and resize() it to fit the parent.
Overload the parents ::resize event handler and re-adjust it there as well.
In the Overlay::paintEvent Draw a big X from corner to corner of the rect()
to prove that it is being resized properly as you resize the parent.

Bill

> I'm a little blind to how I go about putting a widget above another widget.  Assuming I can get step #1 figured out, steps 2-4 look pretty simple...
> 
> Sean
> 
>> 1 - Place a widget over the label widgets in question.
>>
>> 2 - setAttribute(Qt::WA_TransparentForMouseEvents,true);
>>     so that it becomes transparent to mouse events.
>>
>> 3 - Use a transparent background so you can see the widgets beneath.
>>
>> 4 - Draw (animation) on it whatever you want to appear floating
>>     above the widgets beneath and violating the otherwise rigid
>>     rectangular widget boundaries.
>>
>> Bill
>>
>>
>>> I've got a QMainWindow with 5 QLabels on it and a QPushButton.  Call
>> the
>>> QLabels "camera" and "image1" - "image4".  So the idea is that the
>>> "camera" label is always showing a live feed from the digital camera.
>>> When the user presses the pushbutton, a timer starts that snaps four
>>> images over a period of time and puts those images in labels "image1"
>> -
>>> "image4", respectively.  This all works fine, but I wanted to make it
>>> look a little more polished by adding an animation.
>>>
>>> So what I'd like to happen is when the timer fires off to grab an
>> image,
>>> I want that image to appear to move from the "camera" label to the
>>> correct "image" label. So it should appear to jump off from the
>> "camera"
>>> label, float over the top of everything, and land on the desired
>> "image"
>>> label.
>>>
>>> So my first attempt was to override the paintEvent() of my
>> QMainWindow,
>>> create a QPainter and use drawPixmap() to draw my floating image.
>> It's
>>> drawing my image, but the image is showing up under all the child
>>> widgets, instead of over the top of everything.
>>>
>>> Here's my paintEvent() code:
>>>
>>> void MainWindow::paintEvent(QPaintEvent *e)
>>> {
>>>     QMainWindow::paintEvent(e);
>>>     if (showMovingPixmap == true)
>>>     {
>>>         QPainter painter(this);
>>>         painter.setClipping(false);
>>>
>> painter.drawPixmap(movingPixmapXPos,movingPixmapYPos,movingPixmap);
>>>         movingPixmapXPos++;
>>>         movingPixmapYPos++;
>>>     }
>>> }
>>>
>>> So what am I missing?  Would it be easier to change my application to
>>> have a QGraphicsView as the child widget of the QMainWindow, and do
>>> everything on a QGraphicsScene?
>>>
>>> Sean
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>>> Interest at qt-project.org <mailto:Interest at qt-project.org>
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>>>
>>
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