QGraphicsView scale question.

[hickscorp]

Hello sorry for the delay

With your code, i have the very same problem. The item is "stuck" to the top left corner, and only can be dragged off-screen when it is little. When it's bigger than the viewable area, it's draggable but can be sragged off-screen in the top left direction too.

There comes a preview of my code:

void CDlgSettingsImpl::on_btnZoomIn_clicked(void) {
	if (iZoomFactor>=1600)
		return;
	iZoomFactor	*= 2;
	lblZoomLevel->setText(QString::number(iZoomFactor)+"%");
 
	QGraphicsItem*	pPicture;
	QPointF			mapped1, mapped2;
	QRectF			f;
 
	pPicture	= grphVwOriginalPicture->items().first();
	pPicture->scale(2, 2);
	f			= pPicture->boundingRect();
	mapped1		= pPicture->mapToScene(f.topLeft());
	mapped2		= pPicture->mapToScene(f.bottomRight());
	grphVwOriginalPicture->centerOn((mapped2.x()-mapped1.x())/2, (mapped2.y()-mapped1.y())/2);
}
void CDlgSettingsImpl::on_btnZoomOut_clicked(void) {
	if (iZoomFactor<=25)
		return;
	iZoomFactor	/= 2;
	lblZoomLevel->setText(QString::number(iZoomFactor)+"%");
 
	QGraphicsItem*	pPicture;
	QPointF			mapped1, mapped2;
	QRectF			f;
 
	pPicture	= grphVwOriginalPicture->items().first();
	pPicture->scale(.5, .5);
	f			= pPicture->boundingRect();
	mapped1		= pPicture->mapToScene(f.topLeft());
	mapped2		= pPicture->mapToScene(f.bottomRight());
	grphVwOriginalPicture->centerOn((mapped2.x()-mapped1.x())/2, (mapped2.y()-mapped1.y())/2);
}

void CDlgSettingsImpl::on_btnZoomIn_clicked(void) {
	if (iZoomFactor>=1600)
		return;
	iZoomFactor	*= 2;
	lblZoomLevel->setText(QString::number(iZoomFactor)+"%");
	
	QGraphicsItem*	pPicture;
	QPointF			mapped1, mapped2;
	QRectF			f;
	
	pPicture	= grphVwOriginalPicture->items().first();
	pPicture->scale(2, 2);
	f			= pPicture->boundingRect();
	mapped1		= pPicture->mapToScene(f.topLeft());
	mapped2		= pPicture->mapToScene(f.bottomRight());
	grphVwOriginalPicture->centerOn((mapped2.x()-mapped1.x())/2, (mapped2.y()-mapped1.y())/2);
}
void CDlgSettingsImpl::on_btnZoomOut_clicked(void) {
	if (iZoomFactor<=25)
		return;
	iZoomFactor	/= 2;
	lblZoomLevel->setText(QString::number(iZoomFactor)+"%");
	
	QGraphicsItem*	pPicture;
	QPointF			mapped1, mapped2;
	QRectF			f;
	
	pPicture	= grphVwOriginalPicture->items().first();
	pPicture->scale(.5, .5);
	f			= pPicture->boundingRect();
	mapped1		= pPicture->mapToScene(f.topLeft());
	mapped2		= pPicture->mapToScene(f.bottomRight());
	grphVwOriginalPicture->centerOn((mapped2.x()-mapped1.x())/2, (mapped2.y()-mapped1.y())/2);
}

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Can it be a bug with my QT installation? i havnt tested any of the QGraphics framework on linux, so i'm not sure if it's windows only ...

Pierre.

[EDIT:] Maybe the error is here, so here comes how i create the QGraphicsScene & View stuff (In the dialog's constructor):

// Create the original preview objects.
	grphScOriginal			= new QGraphicsScene(this);
	grphVwOriginalPicture	= new QGraphicsView(grphScOriginal, this);
    grphVwOriginalPicture->setFrameShape(QFrame::Panel);
    grphVwOriginalPicture->setVerticalScrollBarPolicy(Qt::ScrollBarAlwaysOff);
    grphVwOriginalPicture->setHorizontalScrollBarPolicy(Qt::ScrollBarAlwaysOff);
    grphVwOriginalPicture->setDragMode(QGraphicsView::ScrollHandDrag);
	grphVwOriginalPicture->setBackgroundBrush(Qt::darkGray);
	fillPreviewFromPlane(grphScOriginal, pInPlane);
 
void CDlgSettingsImpl::fillPreviewFromPlane(QGraphicsScene* grphScToFill, CARGBPlane* pPlane) {
	QList<QGraphicsItem*>	lstItems	= grphScToFill->items();
	while (!lstItems.isEmpty()) {
		QGraphicsItem*	pCurrentItem	= lstItems.takeFirst();
		grphScToFill->removeItem(pCurrentItem);
		delete pCurrentItem;
	}
	QImage		cImage	= QImage(pPlane->Width(), pPlane->Height(), QImage::Format_RGB32);
	byte*	fR	= pPlane->fR;
	byte*	fG	= pPlane->fG;
	byte*	fB	= pPlane->fB;
	for (int iY=0; iY<pPlane->Height(); iY++)
		for (int iX=0; iX<pPlane->Width(); iX++)
			cImage.setPixel(iX, iY, qRgb(*fR++, *fG++, *fB++));
	grphScToFill->addPixmap(QPixmap::fromImage(cImage, Qt::ColorOnly | Qt::ThresholdDither));
}

// Create the original preview objects.
	grphScOriginal			= new QGraphicsScene(this);
	grphVwOriginalPicture	= new QGraphicsView(grphScOriginal, this);
    grphVwOriginalPicture->setFrameShape(QFrame::Panel);
    grphVwOriginalPicture->setVerticalScrollBarPolicy(Qt::ScrollBarAlwaysOff);
    grphVwOriginalPicture->setHorizontalScrollBarPolicy(Qt::ScrollBarAlwaysOff);
    grphVwOriginalPicture->setDragMode(QGraphicsView::ScrollHandDrag);
	grphVwOriginalPicture->setBackgroundBrush(Qt::darkGray);
	fillPreviewFromPlane(grphScOriginal, pInPlane);

void CDlgSettingsImpl::fillPreviewFromPlane(QGraphicsScene* grphScToFill, CARGBPlane* pPlane) {
	QList<QGraphicsItem*>	lstItems	= grphScToFill->items();
	while (!lstItems.isEmpty()) {
		QGraphicsItem*	pCurrentItem	= lstItems.takeFirst();
		grphScToFill->removeItem(pCurrentItem);
		delete pCurrentItem;
	}
	QImage		cImage	= QImage(pPlane->Width(), pPlane->Height(), QImage::Format_RGB32);
	byte*	fR	= pPlane->fR;
	byte*	fG	= pPlane->fG;
	byte*	fB	= pPlane->fB;
	for (int iY=0; iY<pPlane->Height(); iY++)
		for (int iX=0; iX<pPlane->Width(); iX++)
			cImage.setPixel(iX, iY, qRgb(*fR++, *fG++, *fB++));
	grphScToFill->addPixmap(QPixmap::fromImage(cImage, Qt::ColorOnly | Qt::ThresholdDither));
}

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