Re: Draw text on top of both canvas and plot background?

[Elvis S. <elv...@or...>]

Den tis 12 mars 2019 kl 10:59 skrev Uwe Rathmann <Uwe...@ti...>:
>
> > I'm attaching a picture where I've made the canvas background blue to
> > make it clear. The image shows my attempt with overriding paintEvent,
> > note how the "g" is cropped by the canvas which is painted over it.
>
> You have 2 options:
>
> a) Disable the top axis and add a QwtPlotScaleItem instead.
>
> This way the axis would be inside the canvas and you could simply
> overload the label method like posted before without losing any space.
>
> But I'm not sure about this solution as it has a couple of problems, you
> might not want to accept.
>
> b) Add an extra widget for unit text
>
> If you want to draw on top of canvas and scales you need to add an
> additional child widget that is on top of the others:
>
> class UnitLabel : public QWidget
> {
> public:
>      UnitLabel( QwtPlot* plot )
>          : public QWidget( plot )
>      {
>          setAttribute( Qt::WindowTransparentForInput, true );
>          plot->installEventFilter( this );
>
>          adjustSize();
>      }
>
> protected:
>      void paintEvent( QPaintEvent *event ) override
>      {
>          const auto plot = qobject_cast< const QwtPlot* >( parent() );
>          const auto scaleWidget = plot->axisWidget( QwtPlot::yTop )
>
>          QPoint pos = scaleWidget->...
>          pos = mapFrom( scaleWidget, pos );
>
>          QPainter painter;
>          painter.setPen( ... );
>          painter.setFont( ... );
>          painter.drawText( pos, ... );
>      }
>
>      bool eventFilter(QObject *object, QEvent *event) override
>      {
>          if ( object == parent() && event->type() == QEvent::Resize )
>              adjustSize();
>
>          return QWidget::eventFilter();
>      }
>
> private:
>      void adjustSize()
>      {
>          setSize( parentWidget()->size() );
>      }
> };
>
> You will also have to write some code for QwtPlotRenderer - but there
> you don't have any issues with clipping.

Many thanks a lot Uwe for your detailed examples, and sorry if I was
unclear from the start.

Now I know what the approaches are. I will see if the "\nUnit" label
approach is sufficient. If not, I will try your second approach here,
since it sounds cleanest even if it's a bit involved.

Elvis

>
> Uwe
>
>
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