Setting background image for Central Widget

[xfurrier]

Thanks for all your replies. However, despite my efforts and I'm still struggling and there are lots of things I need to learn.

I'm still on the backgrounds and stylesheets (need to use them rather than QPalette). Could you please explain what's the difference between 1) which gives me red background and 2) with the default (grey) background.

1)

MainWindow::MainWindow()
{
	QWidget *w = new QWidget;
	setCentralWidget(w);
	w->setAutoFillBackground(true);
	w->setStyleSheet("background-color: red; ");
}

MainWindow::MainWindow()
{
	QWidget *w = new QWidget;
	setCentralWidget(w);
	w->setAutoFillBackground(true);
	w->setStyleSheet("background-color: red; ");
}

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2)

MainWindow::MainWindow()
{
	CentralContainer *w = new CentralContainer();
	setCentralWidget(w);
	w->setAutoFillBackground(true);
	w->setStyleSheet("background-color: red; ");
}
 
CentralContainer::CentralContainer() : QWidget()
{
}

MainWindow::MainWindow()
{
	CentralContainer *w = new CentralContainer();
	setCentralWidget(w);
	w->setAutoFillBackground(true);
	w->setStyleSheet("background-color: red; ");
}

CentralContainer::CentralContainer() : QWidget()
{
}

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[QAlex]

Hi,
a question:
is it possible to resize automatically a background image inserted with the style sheet instruction
background-image url("..."); ?????
I searched in the documentation, but I found nothing about this issue!

Thanks a lot,
Alex

[rvgrouik]

I created a BackgroundWidget class that does what you want:

#ifndef BACKGROUNDWIDGET_H
#define BACKGROUNDWIDGET_H
 
#include <QWidget>
#include <QPixmap>
#include <QString>
#include <QSize>
#include <QPaintEvent>
 
class BackgroundWidget: public QWidget
{
    Q_OBJECT
 
public:
    BackgroundWidget(QWidget* parent, QString bgImagePath);
    ~BackgroundWidget();
 
 
    void setPicture(const QString& bgImagePath);
    void setPixmap(QPixmap* bgImage);
 
    QSize sizeHint() const;
 
signals:
    void backgroundPainted();
 
protected:
    void paintEvent(QPaintEvent *event);
 
private:
    QPixmap Image;
    QBrush Brush;
};
 
 
#endif // BACKGROUNDWIDGET_H

#ifndef BACKGROUNDWIDGET_H
#define BACKGROUNDWIDGET_H

#include <QWidget>
#include <QPixmap>
#include <QString>
#include <QSize>
#include <QPaintEvent>

class BackgroundWidget: public QWidget
{
    Q_OBJECT

public:
    BackgroundWidget(QWidget* parent, QString bgImagePath);
    ~BackgroundWidget();


    void setPicture(const QString& bgImagePath);
    void setPixmap(QPixmap* bgImage);

    QSize sizeHint() const;

signals:
    void backgroundPainted();

protected:
    void paintEvent(QPaintEvent *event);

private:
    QPixmap Image;
    QBrush Brush;
};


#endif // BACKGROUNDWIDGET_H

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First Ctor arg is your widget (QMainWindow for example), second arg is the path to the picture, possibly stored as resource.

Here is the implementation:

#include "BackgroundWidget.h"
#include <QWidget>
#include <QPixmap>
#include <QString>
#include <QSize>
#include <QPaintEvent>
#include <QPainter>
 
BackgroundWidget::BackgroundWidget(QWidget *parent, QString bgImagePath): QWidget(parent), Image(), Brush()
{
    parentWidget()->stackUnder(this);
    setPicture(bgImagePath);
    setSizePolicy(QSizePolicy::Expanding, QSizePolicy::Expanding);
    lower();
    Brush = QBrush(Image);
}
 
 
BackgroundWidget::~BackgroundWidget()
{
 
}
 
 
QSize BackgroundWidget::sizeHint() const
{
    return parentWidget()->visibleRegion().boundingRect().size();
}
 
void BackgroundWidget::setPicture(const QString& bgImagePath)
{
    Image = QPixmap(bgImagePath);
}
 
void BackgroundWidget::setPixmap(QPixmap* bgImage)
{
    if (! bgImage)
        return;
    Image = QPixmap(*bgImage);
}
 
void BackgroundWidget::paintEvent(QPaintEvent *event)
{
    resize(parentWidget()->visibleRegion().boundingRect().size());
    QPainter painter(this);
    painter.setBrush(Brush);
    int x = (width() - Image.width()) / 2;
    int y = (height() - Image.height()) / 2;
    painter.drawPixmap(x, y, Image.width(), Image.height(), Image);
    emit backgroundPainted();
}

#include "BackgroundWidget.h"
#include <QWidget>
#include <QPixmap>
#include <QString>
#include <QSize>
#include <QPaintEvent>
#include <QPainter>

BackgroundWidget::BackgroundWidget(QWidget *parent, QString bgImagePath): QWidget(parent), Image(), Brush()
{
    parentWidget()->stackUnder(this);
    setPicture(bgImagePath);
    setSizePolicy(QSizePolicy::Expanding, QSizePolicy::Expanding);
    lower();
    Brush = QBrush(Image);
}


BackgroundWidget::~BackgroundWidget()
{

}


QSize BackgroundWidget::sizeHint() const
{
    return parentWidget()->visibleRegion().boundingRect().size();
}

void BackgroundWidget::setPicture(const QString& bgImagePath)
{
    Image = QPixmap(bgImagePath);
}

void BackgroundWidget::setPixmap(QPixmap* bgImage)
{
    if (! bgImage)
        return;
    Image = QPixmap(*bgImage);
}

void BackgroundWidget::paintEvent(QPaintEvent *event)
{
    resize(parentWidget()->visibleRegion().boundingRect().size());
    QPainter painter(this);
    painter.setBrush(Brush);
    int x = (width() - Image.width()) / 2;
    int y = (height() - Image.height()) / 2;
    painter.drawPixmap(x, y, Image.width(), Image.height(), Image);
    emit backgroundPainted();
}

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See attachment for complete code

rvgrouik