Issues with QScrollArea and custom widget

Joel Bodenmann

I just checked (using qDebug() inside UGfxDisplay::paintEvent()) and they (UGfxDisplay::_width() and UGfxDisplay::width()) are always the same value (and they don't change when zooming).
Keep in mind that UGfxDisplay::width() returns the width of my virtual display which is not supposed to change even if the person zooms in. This is not like QWidget::width() which would return _width * _scale (which it does as I always call QWidget::setFixedSize(_scale*_width, _scale*_height).

I assume that QScrollArea calls QWidget::width() and not UGfxDisplay::width() as it only has the pointer to the QWidget anyway.

Renaming my width() and height() methods would be quite an effort as they are used on many places. Is the QtCreator refactoring algorithm up to the task? ;)

kshegunov

No idea, my code is usually so bad it doesn't need refactoring but plain rewriting. ;)

Anyway, forget that for a moment, can you try something like this:

painter.drawImage(event->rect(), img, img.rect().intersected(event->rect()));

Joel Bodenmann

@kshegunov said in Issues with QScrollArea and custom widget:

No idea, my code is usually so bad it doesn't need refactoring but plain rewriting. ;)

Still waiting on my QAbstractModel merging thingy ;)

Anyway, forget that for a moment, can you try something like this:

Here you go: https://www.screencast.com/t/nNbHckWi

kshegunov

@Joel-Bodenmann said in Issues with QScrollArea and custom widget:

Still waiting on my QAbstractModel merging thingy ;)

I know, I know.

Here you go: https://www.screencast.com/t/nNbHckWi

Well, something moved at least. Can you get the paint rects you get when zoomin in/out and when you scroll up/down/left/right along with the image rects and dump them all into a file?

SGaist

Hi,

Might be a silly question but how are you handling UGfxDisplay ?

Joel Bodenmann

@kshegunov said in Issues with QScrollArea and custom widget:

Well, something moved at least. Can you get the paint rects you get when zoomin in/out and when you scroll up/down/left/right along with the image rects and dump them all into a file?

Sure, I'll get that done.

@SGaist said in Issues with QScrollArea and custom widget:

Might be a silly question but how are you handling UGfxDisplay ?

I'm sorry, I don't understand what handling means in this context. Can you be more specific?

SGaist

Are you calling something like _centralScrollArea->setWidget(_myGDisplay); ?

Then, are you sure that you should handle the scaling in GDisplay ?

When zooming, what about having something like _myGDisplay->resize(_scale * _sourceSize); So you only handle painting in that widget.

Joel Bodenmann

@kshegunov said in Issues with QScrollArea and custom widget:

Well, something moved at least. Can you get the paint rects you get when zoomin in/out and when you scroll up/down/left/right along with the image rects and dump them all into a file?

Here you go: http://paste.ugfx.io/show/a5113bcc08

@SGaist said in Issues with QScrollArea and custom widget:

Are you calling something like _centralScrollArea->setWidget(_myGDisplay); ?

Yep, that's what I am doing.

@SGaist said in Issues with QScrollArea and custom widget:

When zooming, what about having something like _myGDisplay->resize(_scale * _sourceSize); So you only handle painting in that widget.

In my opinion that won't work as it will not scale up the contents inside of my UGfxDisplay. Keep in mind that the QPixmap I draw in my UGfxDisplay::paintEvent() is the content of a virtual display. That virtual display has a given size (width and height) in pixels. When zooming in I need to scale up everything. I don't display more of the widget, I just display the same content bigger.

kshegunov

Have you noticed your image doesn't grow (or shrink)?

Joel Bodenmann

The image is not supposed to grow. The image represents the contents of the virtual display. It will always have the same amount of pixels no matter how much I zoom into the UGfxDisplay widget. My virtual display does not grow by zooming into it :p

kshegunov

But why are you ~~redrawing~~ reinitializing it at each paint event then? It got me confused, now I believe I know what you want. Should be something like this (I *think*):

painter.drawImage(event->rect(), img, event->rect() / _scale);

PS. Or not. I need to think.
PS. After thinking:

QRect paintRect = event->rect();
QRect sourceRect(paintRect.topLeft() / _scale, paintRect.size() / _scale);
painter.drawImage(paintRect, img, sourceRect);

Joel Bodenmann

Wooo, I love you \o/ (still, not again, don't worry honey)

This is with your "After thinking" code: https://www.screencast.com/t/cEAa2z4Zd

In retrospect this seems somewhat obvious...

kshegunov

@Joel-Bodenmann said in Issues with QScrollArea and custom widget:

Wooo, I love you

Nice! Love and world peace and such things. ;)

In retrospect this seems somewhat obvious...

Yes, quantum mechanics also seems rather obvious to me ... after a few people thought and invented it. ;)

Joel Bodenmann

@kshegunov said in Issues with QScrollArea and custom widget:

Yes, quantum mechanics also seems rather obvious to me ... after a few people thought and invented it. ;)

invented? ;)
Too bad those people didn't teach you how to write nice code though :p

Thank you for your help guys, much appreciated!

kshegunov

@Joel-Bodenmann said in Issues with QScrollArea and custom widget:

Too bad those people didn't teach you how to write nice code though :p

This is all a fault of my own, sadly, but hey life's not all roses ... :)

Thank you for your help guys, much appreciated!

You are welcome. Now go and make us proud! ;D