QPixmap::operator=: Cannot assign to pixmap during painting

[hannesvdc]

Hey,

I'm currently making my own tablewidget because i want to have more than a thousand rows and columns and QTableWidget takes too much memory.
So i started working on it, and this is what i currently have:

//mytable.cpp
#include <QtGui/QApplication>
#include <QtGui/QMainWindow>
#include <QtGui/QColor>
#include <QtGui/QBrush>
#include "mytable.h"
 
mytable::mytable( QWidget* parent) : QWidget( parent ) {
}
 
void mytable::paintEvent( QPaintEvent* event ) {
	QPainter* painter=new QPainter(this);
	QSize _size = size();
	QBrush brush( QColor(0,150,0)/*, Qt::LinearGradientPattern*/);
	painter->fillRect(0,0, _size.width(), 20, brush );
	painter->fillRect(0,0, 30, _size.height() , brush);
	painter->setPen(QColor(0,0,0));
	for( int x = 30; x<= _size.width();x+=80 ) {
		painter->drawLine( x, 0, x, _size.height() );
	}
	for( int y = 20; y <= _size.height(); y+=20){
		painter->drawLine(0, y, _size.width(), y );
	}
}
 
/*void mytable::drawHeaders( QPainter* painter, QSize _size ) {
 
}*/	
int main( int argc, char** argv) {
	QApplication app( argc, argv );
	QMainWindow w;
	w.setGeometry(0,0,600,600);
	mytable table( &w );
	table.setGeometry(0,0,600,600);
	w.show();
	return app.exec();
}

//mytable.cpp
#include <QtGui/QApplication>
#include <QtGui/QMainWindow>
#include <QtGui/QColor>
#include <QtGui/QBrush>
#include "mytable.h"

mytable::mytable( QWidget* parent) : QWidget( parent ) {
}

void mytable::paintEvent( QPaintEvent* event ) {
	QPainter* painter=new QPainter(this);
	QSize _size = size();
	QBrush brush( QColor(0,150,0)/*, Qt::LinearGradientPattern*/);
	painter->fillRect(0,0, _size.width(), 20, brush );
	painter->fillRect(0,0, 30, _size.height() , brush);
	painter->setPen(QColor(0,0,0));
	for( int x = 30; x<= _size.width();x+=80 ) {
		painter->drawLine( x, 0, x, _size.height() );
	}
	for( int y = 20; y <= _size.height(); y+=20){
		painter->drawLine(0, y, _size.width(), y );
	}
}

/*void mytable::drawHeaders( QPainter* painter, QSize _size ) {
	
}*/	
int main( int argc, char** argv) {
	QApplication app( argc, argv );
	QMainWindow w;
	w.setGeometry(0,0,600,600);
	mytable table( &w );
	table.setGeometry(0,0,600,600);
	w.show();
	return app.exec();
}

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//mytable.h
#ifndef MYTABLE_H
#define MYTABLE_H
 
#include <QtGui/QWidget>
#include <QtGui/QPainter>
 
class mytable : public QWidget {
 
public:
	mytable(QWidget*);
protected:
	void paintEvent( QPaintEvent* );
	void drawHeaders(QPainter*, QSize );
 
};

//mytable.h
#ifndef MYTABLE_H
#define MYTABLE_H

#include <QtGui/QWidget>
#include <QtGui/QPainter>

class mytable : public QWidget {
	
public:
	mytable(QWidget*);
protected:
	void paintEvent( QPaintEvent* );
	void drawHeaders(QPainter*, QSize );

};

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Compiling works fine, but if i run, the widget shows up, but i get the following error
if i resize the widget:

QPixmap::operator=: Cannot assign to pixmap during painting

QPixmap::operator=: Cannot assign to pixmap during painting

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And this error if i close the widget:

QPaintDevice: Cannot destroy paint device that is being painted

QPaintDevice: Cannot destroy paint device that is being painted

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What can i do to solve this errors?

regards, hannesvdc

[JackHammer]

I think its because you are not deleting pointer to QPainter inside paintEvent().

[hannesvdc]

Hey, thanks, a call to painter->end or delete painter solves to problem!

regards, hannesvdc