drawing lines over child widgets ?

Markus Gustavsson mighty at fragzone.se
Thu Jun 8 16:08:49 UTC 2000


Thorsten Gecks wrote:
> 
> How can I draw lines in a widget over(!) its child widgets ?
> 
> The answer to this question is important for my programming at all.
> 
> Thanks,
> 
> thorsten
> 
> t_gecks at informatik.uni-kl.de

I don't think it's possible do do that kind of line drawing afaik, 
however, you may be able to acheive the same result with a little
trick, although it's slower than if it could have been drawn right
through a child widget (probably not noticeable slower if you aren't
writing something which needs to move and update really fast).

#####################################################

background.h:

#ifndef BACKGROUND_H
#define BACKGROUND_H

#include <qwidget.h>
#include <qgroupbox.h>
#include <qcheckbox.h>
#include <qpixmap.h>

class Background
{
        public:

        Background();
        ~Background();

        void parse(QWidget *dst, QWidget *src);
        void parse(QGroupBox *dst, QWidget *src);
        void parse(QCheckBox *dst, QGroupBox *src);

        private:

        QPixmap *map;
};

#endif

background.cpp:

#include "background.h"

Background::Background()
{
        map = new QPixmap();
}

Background::~Background()
{
        delete map;
}

void Background::parse(QWidget *dst, QWidget *src)
{
        map->resize(dst->width(), dst->height());
        bitBlt(map, 0, 0, src->backgroundPixmap(), dst->x(), dst->y(), dst->width(), dst->height());
        dst->setBackgroundPixmap(*map);
}

void Background::parse(QGroupBox *dst, QWidget *src)
{
        map->resize(dst->width(), dst->height());
        bitBlt(map, 0, 0, src->backgroundPixmap(), dst->x(), dst->y(), dst->width(), dst->height());
        dst->setBackgroundPixmap(*map);
}

void Background::parse(QCheckBox *dst, QGroupBox *src)
{
        map->resize(dst->width(), dst->height());
        bitBlt(map, 0, 0, src->backgroundPixmap(), dst->x(), dst->y(), dst->width(), dst->height());
        dst->setBackgroundPixmap(*map);
}

#####################################################

You get the trick? Just add new rules for all widget types
you need to have copied up from the background.
Create a Background object in your class, then paint the
base widget, and recursivly call Background::parse() on all
of the childs. You might want to add these recursive parse()
calls to the mothers resizeEvent() to have it realigned each
time it's rezised by the user.
I don't know if this helps, but's it's possibility that you
might fins this usefull as a placebo for drawing real lines
through childwidgets (which I don't think can be done).

Example, http://mag.cx/~mighty/backparsed.jpg

		/Markus




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