Painting: How to control what's in the foreground?

[Mister_Crac]

I am writing a program that displays several QWidgets on the screen, within one parent QWidget. Then I have a QLabel that I draw with the drawText() method from QPainter. There are als Buttons to move around this Label on the screen (up, down, left, right).
Like so:

void MyClass::paintEvent(QPaintEvent*)
{
	QPainter painter(this);
	painter.setBrush(Qt::red);
	QPen myPen;
	myPen.setWidth(1);
	myPen.setColor(foreground);
	painter.setPen(myPen);
	painter.drawText(xpos, ypos, textDisplay->text());
}

void MyClass::paintEvent(QPaintEvent*)
{
	QPainter painter(this);
	painter.setBrush(Qt::red);
	QPen myPen;
	myPen.setWidth(1);
	myPen.setColor(foreground);
	painter.setPen(myPen);
	painter.drawText(xpos, ypos, textDisplay->text());
}

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Now, the QWidgets are always shown in the foreground, and the QLabel is shown in the background, behind the QWidgets. How can I change this order? I want the QLabel to be in the foreground.
Common sense tells you that whichever Object gets to be painted last should be in the foreground, since it is drawn "on top" of the other ones. How does one achieve this?

[jpn]

One can change the stacking order of children with QWidget::raise() and QWidget::lower().

[Mister_Crac]

Sounds good, but it does not seem to do the trick. I have added this method call to paintEvent():

textDisplay->raise();

textDisplay->raise();

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But it still gets painted below the other widgets, not on top. See this Screenshot: http://img156.imageshack.us/img156/3...picturedf4.png

[jpn]

Sounds good, but it does not seem to do the trick.
I have added this method call to paintEvent():

textDisplay->raise();

textDisplay->raise();

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You don't want to do that during every single paint event. It would only cause unnecessary overhead.

But it still gets painted below the other widgets, not on top. See this Screenshot: http://img156.imageshack.us/img156/3...picturedf4.png

Children are always on top of their parent. From the attached screenshot it's impossible to see which widget is a children of which parent. So what are MyClass and textDisplay? You are raising textDisplay but MyClass actually draws the text?

[Mister_Crac]

You don't want to do that during every single paint event. It would only cause unnecessary overhead.

Okay, but where do I call raise()? Within the constructor?

Children are always on top of their parent. From the attached screenshot it's impossible to see which widget is a children of which parent. So what are MyClass and textDisplay? You are raising textDisplay but MyClass actually draws the text?

The QLabel textDisplay is a member of MyClass. In the constructor of MyClass, I create the widgets that are shown as black in the screenshot (Bus, Prozessor etc.) and arrange them in a layout. So that makes them child widgets - right? The textDisplay is not integrated into the layout.
The one widget that is supposed to move around is textDisplay, so it is the only one that gets drawn in the paintEvent() method.

[jpn]

Okay, but where do I call raise()? Within the constructor?

Yeah, it's enough change the stacking order once. Somewhere near creating the widgets is fine.

The QLabel textDisplay is a member of MyClass. In the constructor of MyClass, I create the widgets that are shown as black in the screenshot (Bus, Prozessor etc.) and arrange them in a layout. So that makes them child widgets - right? The textDisplay is not integrated into the layout.
The one widget that is supposed to move around is textDisplay, so it is the only one that gets drawn in the paintEvent() method.

So if MyClass is the parent, anything it draws (the red text) appears below it's children. Each widget is responsible for drawing itself when it receives a paint event. You don't paint other widgets, like children in the paintEvent() of the parent. Where is the textDisplay widget in the screenshot? Maybe you have to call QWidget::adjustSize() or something to make it adjust it's size to correspond it's contents (this would be done automatically if it was in a layout).

[Mister_Crac]

Where is the textDisplay widget in the screenshot?

It's the big red letters :-)

Maybe you have to call QWidget::adjustSize() or something to make it adjust it's size to correspond it's contents (this would be done automatically if it was in a layout).

I somehow fear that moving around a widget that is part of a layout will break the layout, no? I will try it out now.

[jpn]

It's the big red letters :-)

Are you sure? So where is the red text drawn in MyClass::paintEvent()?

I somehow fear that moving around a widget that is part of a layout will break the layout, no? I will try it out now.

No, you can't move a widget managed by a layout.

[jpn]

Could you please do somewhere in MyClass after creating all the labels and other child widgets:

dumpObjectTree();

dumpObjectTree();

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and paste the output?

[Mister_Crac]

Okay I'm not sure if I came across clearly. I have made another screenshot and this time, I have changed all the German words to English for better understanding. Also, the first time around I did not show all of the windows that my application so far has. Here is the new and complete screenshot:

http://img502.imageshack.us/img502/4...icture2nf4.png

As you can see, the red text could really be anything. Anything you type in. It could also be another color if you want to. In any case, I definitely need it to be freely movable. Up, down, left, right, you name it. So it cannot be part of a layout, as it seems. All the other widgets - Memory, CPU, I/O Unit, Bus, Arrows - however can and in fact, are.

Now, the problem remains: How can I achieve it so that the QLabel gets drawn on top of the other widgets? Calling raise() did not lead to success so far.

Also,

Could you please do somewhere in MyClass after creating all the labels and other child widgets:

dumpObjectTree();

dumpObjectTree();

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and paste the output?

Would the output of that command happen to be found in the directory which is named "debug"? Then I fear that my Qt library is maybe not compiled for debugging, because that directory is empty always.

[jpn]

Would the output of that command happen to be found in the directory which is named "debug"? Then I fear that my Qt library is maybe not compiled for debugging, because that directory is empty always.

No, I was referring to the debug output. IDEs tend to show the debug output. If you're not using any IDE, on Windows you will have to add

CONFIG += console

in the .pro file, regenerate makefile and rebuild the application. An external console is launched together with the application from which you can see the debug output. Alternatively, you can use such utilities as DebugView to monitor the debug output.