[Qt-jambi-interest] Widget Size 0? How to show large pixmpa in a small viewport without loosing pixmap data

[Eskil Abrahamsen Blomfeldt]

Hi, Dawid.

Dawid Sip wrote:
> GraphicsView -pos(150,200) I can transform this down to the item and 
> get somethink like pos(1250x1000). So I somehow need to adjust the 
> projection. I think this is an issue of the viewport. I think I could 
> achieve this by changing the viewport to QGLWidget and with help of 
> some wrapper lib. like JOGL adjust the viewport/frustum, but I'd 
> rather not use OpenGL in my application. So is this the only way or 
> can I still do this with the default QWidget as viewport?
>
> Sow the question is: "How to show large pixmpa in a small viewport 
> without loosing pixmap data"
>
> Could somebody please point me in the right direction?
>

The graphics view has the possibility of setting any transform/matrix on 
it to alter how and which part of the scene is displayed. For your 
particular case there is also a convenience method which sets the 
correct scale on the view so that a specific item fits perfectly inside it.

    
http://doc.trolltech.com/qtjambi-4.4.0_01/doc/html/com/trolltech/qt/gui/QGraphicsView.html#fitInView(com.trolltech.qt.gui.QGraphicsItemInterface)

I have attached a modification to the previous example of how you can 
use this method to achieve what you need. Please make sure you set the 
scrollbar policy of the view to no scrollbars in both vertical and 
horizontal direction, though, otherwise you will get an infinite stream 
of resize events as the scrollbars automatically switch on and off.

Hope this helps.

-- Eskil

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