[Interest] Issue painting over child widgets

Murphy, Sean M. sean.murphy at gd-ais.com
Thu Nov 17 19:43:07 CET 2011


Can you explain a little more your render() idea?  I'm assuming you mean I take my entire application, render it to a pixmap, and somehow paint that over the top of all the real widgets?  So the user would always be looking at a picture of what my application looks like?  If so, I'm still a bit confused by how I'd render this pixmap on top of the existing widgets, since that's fundamentally the only issue I'm having with my current implementation.

As far as the QGraphicsView technique, I'm all set with that.  It's just not the path I went down initially, so I was hoping there was just some sort of "PaintOverChildren" flag that I needed to set that would fix my issue with one line of code, without having to transition everything over to the GraphicsView framework.

Sean

From: Jason H [mailto:scorp1us at yahoo.com]
Sent: Thursday, November 17, 2011 11:05 AM
To: Murphy, Sean M.; interest at qt-project.org
Subject: Re: [Interest] Issue painting over child widgets

Parents paint first, then children.

However what you can do is create the layout of widgets you need, then render() that parent widget to a pixmap, which you then combine in your own overlay class with what ever you need to overlay. You then take the mouse events and send them as needed to the controls.

However with QGraphicsView you can do all that, even more easily.

________________________________
From: "Murphy, Sean M." <sean.murphy at gd-ais.com>
To: "interest at qt-project.org" <interest at qt-project.org>
Sent: Thursday, November 17, 2011 10:50 AM
Subject: [Interest] Issue painting over child widgets

I'm trying to create an animation effect for a Photo Booth application, and I'm having trouble getting the animation to paint over child widgets.  Here's the setup:

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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