[Qt-interest] aspect-ratio for graphs

[phil prentice]

Thanks
  Sean
Thats brilliant I will try it now. Please ignore my last post...I will plug 
this into my example!!!!
Thanks very much for your time

Phil

On Thursday 15 July 2010 11:44, Sean Harmer wrote:
> On Thursday 15 July 2010 11:55:15 phil prentice wrote:
> > Sorry Sean
> >   Finger/Brain trouble...
>
> No worries.
>
> >   Indeed I am trying to use heightForWidth()...See my original mail which
> > has a derived object within a layout.  I am cutting it down though and
> > will continue to try and get it to work.  If no success I will mail the
> > cut down version of my code. If I am successful I will also provide the
> > code. Thanks for your help
>
> OK I have got an example of how to do this for you - see attached tarball.
>
> The key is to set a suitable size policy in your custom widget (be it
> derived from QWidget or from QGraphicsView) and to implement the int
> heightForWidth( int w ) function.
>
> In the attached example I derived a class FixedAspectWidget from QWidget.
> The ctor and heightForWidth() functions look like this:
>
> FixedAspectWidget::FixedAspectWidget(QWidget *parent) :
>     QFrame(parent)
> {
>     setMinimumSize( 100, 100 );
>     QSizePolicy policy( QSizePolicy::Preferred, QSizePolicy::Minimum );
>     policy.setHeightForWidth( true );
>     setSizePolicy( policy );
> }
>
> int FixedAspectWidget::heightForWidth(int w) const
> {
>     return w;
> }
>
> That is you have to call QSizePolicy::setHeightForWidth( true ). This then
> tells any layout into which you place your widget that the layout needs to
> call your widget's heightForWidth() function which in this case simply
> returns the input width resulting in a square widget.
>
> This of course only provides you with a widget of fixed aspect ratio,
> drawing your graphs with a fixed aspect ratio is a whole other problem when
> you consider axis labels, ticks, titles, different coordinate systems etc.
>
> HTH,
>
> Sean
>
> > Phil
> >
> > On Thursday 15 July 2010 10:34, you wrote:
> > > Hi Phil,
> > >
> > > please reply to the list not to me personally.
> > >
> > > On Thursday 15 July 2010 11:22:10 phil prentice wrote:
> > > > Thanks Sean
> > > >
> > > >   Will it help me with my aspect-ratio problem....because if it does
> > > >   then
> > > >
> > > > I would definitely use it.  Its the aspect-ratio problem I would like
> > > > to solve...I need my graphs to have aspect-ratio of 1:1(inside a
> > > > layout).  I could not see how QGraphicsView can help me there???
> > > > Please tell me that I am wrong!!!
> > >
> > > QGraphicsView itself is just a QWidget so it will not support fixed
> > > aspect ratio of the widget itself out of the box - you'll still need to
> > > use something like heightForWidth() to implement that.
> > >
> > > You can make the graphs within your scene fixed aspect ratio quite
> > > easily though. Can you provide a .ui file that shows the kind of layout
> > > you would like?
> > >
> > > > I am still trying to play, but as of yet not getting anywhere
> > >
> > > I have no time to look at this right now but I may be able to later.
> > >
> > > Cheers,
> > >
> > > Sean
> >
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