Custom widget in QScrollArea

ElRudi

Hi,

i create a widget in a QScrollArea that should fill the entire widget with red color, but when i scroll to the right, i see that it's not filled completely. The frame is drawn correctly. Here is my code:

#include <QMainWindow>
#include <QPainter>
#include <QScrollArea>

class MyWidget : public QWidget
{
public:

	virtual void paintEvent(QPaintEvent* e)
	{
		QPainter painter(this);
		painter.fillRect(geometry(), Qt::red);
	}
};

class ScrollTest : public QMainWindow
{
	Q_OBJECT

public:
	ScrollTest(QWidget *parent = 0)	: QMainWindow(parent)
	{
		setGeometry(QRect(100,100,230,230));

		MyWidget* widget = new MyWidget;
		widget->setGeometry(QRect(0,0, 250, 250));
		widget->setStyleSheet("border: 3px solid blue;");

		QScrollArea* area = new QScrollArea(this);
		area->setGeometry(QRect(0,0, 200, 200));
		area->setWidget(widget);
	}
};

Here is a Screenshot: image

What's wrong?

Edit raven-worx: added code tags

raven-worx

did you try QScrollArea::setWidgetResizable(true)?

But the question is what you want to achieve, because actually a scrollarea's purpose is to show scrollbars if needed.

If setWidgetResizable() doesn't do what you want you need to subclass QScrollArea and reimplement it's resizeEvent() handler and resize the widget manually.

ElRudi

This is just a simple test dialog that shows my problem. The real widget is an image viewer/editor. I tried QLabel to draw the image, but this is very slow when you zoom in with large images. What i want to do is to zoom and scroll through the image.

If i call setWidgetResizable(true) i don't see the scrollbars and only a portion of the widget.

ElRudi

The solution is:

painter.fillRect(QRect(0,0, width(), height()), Qt::red);

geometry() delivers negative x/y values.