I'm trying to move a QGraphicsItem with the mouse hover over the parent item.
BaseItem::BaseItem(const QRectF &bounds)
: theBounds(bounds), theMousePressed(false)
{
theLineItem = new LineItem(theBounds, this);
setAcceptHoverEvents(true);
}
and
void BaseItem::hoverEnterEvent(QGraphicsSceneHoverEvent *event)
{
QPointF position = mapToScene( event->pos());
theLineItem->setPos( position);
}
But the item is not moving. Is there any other way to move the item on the scene with mouse move, without using the ItemIsMovable flag, because I want the item to be moved around the parent item, once it's invoked?
When you create the LineItem, in its constructor you pass the BaseItem as the parent.
A call to setPos on a GraphicsItem, sets the position of the item relative to its parent which, in this case, is the BaseItem.
Mapping the event->pos() to scene coordinates is wrong here. event->pos() returns the position in local coordinates of the receiving object, which in this case is the BaseItem.
Therefore, you should be setting the position of theLineItem directly with event->pos().
theLineItem->setPos(event->pos());
Note that if you did happen to want the event position in scene coordinates, there's a function already available: -
event->scenePos();
So you would not have needed to call mapToScene.
Related
I would like to have certain things drawn on QGraphicsScene, but not be QGraphicsItem (it would interfere with the processing of the QGraphicsItem collection).
Example: a scene bounding rectangle, a grid
I am overriding the drawBackground(QPainter *painter, const QRectF &rect) for that purpose. (I should subclass the scene... )
void MyView::showHideBounds()
{
m_showBackgroundBounds = !m_showBackgroundBounds;
// can't triger an update ???
update(); // neither does anything
viewport()->update();
}
void MyView::drawBackground(QPainter *painter, const QRectF &rect)
{
QPen pen;
if(m_showBackgroundBounds)
pen = QPen(QColor(0, 0, 0), 10, Qt::PenStyle(Qt::SolidLine));
else
pen = QPen(QColor(255, 255, 255), 10, Qt::PenStyle(Qt::SolidLine));
painter->setPen(pen);
painter->drawRect(QRect(QPoint(-scene()->sceneRect().size().toSize().width()/2,
-scene()->sceneRect().size().toSize().height()/2),
scene()->sceneRect().size().toSize()));
}
I would like the option to show/hide either the bounding rectangle or the grid.
The only thing I can think of is paint over them with the color of the background brush ? Is there any other option ?
As I have written it above, it works - except I need user action on items (or a zoom or some other scene changing action) to trigger refresh, or call an update... (the function showHideBounds doesn't - not sure how to make it force a refresh)
I would call the drawBackground from the showHideBounds function - but I don't know how to get the painter
[Also, the drawBackground seems to be drawn automatically... how can I give it the rect argument it needs ? (it seems if I draw the rect it does draw the scene rectangle but I only see the right and bottom edges)]
In order to redraw a particular section of scene, you can call
QGraphicsScene->invalidate(rect_to_redraw, Backgroundlayer)
Note that if drawBackground(*painter, rect) paints over area outside rect, it will not update automatically. In that case invalidate has to be called with appropriate rect parameters.
I am trying to find the items under the mouse in a scene. The code I am using is as follows:
QPainterPath mousePath;
mousePath.addEllipse(mouseEvent -> pos(),5,5);
QList<QGraphicsItem *> itemsCandidate = this->items(mousePath);
if (!(itemsCandidate.contains(lastSelectedItem))) lastSelectedItem =itemsCandidate.first();
PS: this refers to a scene.
The code should find the items intersected by a small circle around the mouse position and keep the item pointer unchanged if the previous intersected one is still intersected, or take the first in the QList otherwise.
Unfortunately, this code does not work with items inside each other. For example, if I have a Rect side a Rect, the outer Rect is always intersecting the mouse position even when this one is near the inner Rect. How can i solve this?
UPDATE: This seems not to be a problem with polygons, but with Rect, Ellipses, etc.
UPDATE: This code is in the redefined scene::mouseMoveEvent
You can reimplement mouseMoveEvent in QGraphicsView to capture mouse move events in view and track items near the mouse like:
void MyView::mouseMoveEvent(QMouseEvent *event)
{
QPointF mousePoint = mapToScene(event->pos());
qreal x = mousePoint.x();
qreal y = mousePoint.y();
foreach(QGraphicsItem * t , items())
{
int dist = qSqrt(qPow(t->pos().x()-x,2)+qPow(t->pos().y()-y,2));
if( dist<70 )
{
//do whatever you like
}
}
QGraphicsView::mouseMoveEvent(event);
}
I use Qt and I want to move some object with mouse. For example, user clicks on object and drag this object to another place of window. How I can do it?
I tried mouseMoveEvent:
void QDropLabel::mouseMoveEvent(QMouseEvent *ev)
{
this->move(ev->pos());
}
but unfortunately object moves very strange way. It jumps from place to place.
QDropLabel inherits QLabel. Also it has given a pixmap.
I tried to do it with different objects, but result is same.
Your movable widget must have a QPoint offset member. It will store a position of the cursor click relative to the widget's top left corner:
void DropLabel::mousePressEvent(QMouseEvent *event)
{
offset = event->pos();
}
On mouse move event you just move your widget in its parent coordinate system. Note that if you don't subtract offset from the cursor position, your widget will 'jump' so its top left corner will be just under the cursor.
void DropLabel::mouseMoveEvent(QMouseEvent *event)
{
if(event->buttons() & Qt::LeftButton)
{
this->move(mapToParent(event->pos() - offset));
}
}
I have a QGraphicsView and a QGraphicsScene connected like this:
graphicsScene->setSceneRect(this->graphicsView->rect());
graphicsView->setScene(this->Scene);
Then I load an image and add it to the scene:
QPixmap pixmap;
pixmap.load(fileName);
pixmap = pixmap.scaled(this->graphicsView->size());
QGraphicsPixmapItem* item = this->Scene->addPixmap(pixmap);
Now, as described in the documentation, the image corner is at (0,0), which is not the corner of the graphicsScene. I know I can position the resulting pixmap by doing:
item->setPos(this->Scene->sceneRect().x(), this->Scene->sceneRect().y());
However, I can't seem to make sense of the coordinates of the rect's of the scene or the view. Can anyone explain how I would move the pixmap to the corner of the scene/view?
Thanks,
David
EDIT: Here is the full form constructor. The QGraphicsView was created in Qt Designer and is inside of a GridLayout:
Form::Form(QWidget *parent)
: QWidget(parent)
{
setupUi(this);
QGraphicsScene* scene = new QGraphicsScene;
scene->setSceneRect(this->graphicsView->rect());
this->graphicsView->setScene(scene);
QPixmap pixmap;
pixmap.load("image.png");
pixmap = pixmap.scaled(this->graphicsView->size());
scene->addPixmap(pixmap);
}
I also tried this:
QGraphicsScene* scene = new QGraphicsScene;
this->graphicsView->setScene(scene);
QPixmap pixmap;
pixmap.load("/home/doriad/glasses.jpg");
QGraphicsPixmapItem * item = scene->addPixmap(pixmap);
this->graphicsView->fitInView (item);
but the image appears tiny, rather than filling up the view like I would expect. Can anyone explain this?
The full project and image are available here: daviddoria.com/Uploads/qt/QPixmapPosition
Don't worry about scaling the pixmap yourself or even translating it, let the view do it for you.
Use graphicsView->fitInView(pixmap); but you should read the documentation for :
Qt's Graphics View Framework
void QGraphicsView::setSceneRect (QRectF )
void QGraphicsView::translate ( qreal dx, qreal dy )
void QGraphicsView::fitInView ( const QGraphicsItem * item, ... )
The way that QGraphicsScene and QGraphicsView interact is that you can have a single scene with at least one or more views.
A good example I like to think of is a zoomed in view of part of a map with a mini view of the entire map in the corner. There are two views, one of part of the map and one of the entire map, with one scene, the map itself.
So you put items in your scene and all the items in the scene are drawn relative in size to each other. The "scene rect" of your view, by default, scales to fit the items in the view until one unit in the scene is one pixel in the view or until it needs to zoom out to fit all the items in your scene.
If you call fitInView(someItem) it should scale your view of the scene so that the item specified fills it up and translates the view so that it is centered. If you need to translate or scale it more use the translate or scale functions in QGraphicsView.
When you are jumping between coordinate systems of your scene and view with your QRect's or QPoint's, use the helper functions: mapToScene and mapFromScene from QGraphicsView.
Try this:
QGraphicsScene* scene = new QGraphicsScene;
scene->setSceneRect(graphicsView->sceneRect());
QPixmap pixmap;
pixmap.load("/home/doriad/glasses.jpg");
pixmap=pixmap.scaledToWidth(this->graphicsView->width());
QGraphicsPixmapItem * item = scene->addPixmap(pixmap);
graphicsView->setScene(scene);
By default, the pixmap will be at (0,0) in the scene, and the scene will be at (0,0) in the view. QWidgets are sized by pixels. If you had a QGraphicsView the size of the screen and the resolution is 1440 x 900, you can position objects in that view from (0,0) or the top left corner of the screen, to (1440,900) the bottom right corner of the screen. Most QGraphicsItems are placed with reference to their top left corner. So placing a pixmap at (0,0) aligns the top left corner of the pixmap with the top left corner of the scene it's placed in. If your pixmap 'hangs off the bottom' of your view, try using:
pixmap=pixmap.scaledToHeight(this->graphicsView->height());
If you use the function:
this->graphicsView->fitInView (item);
The graphicsView will only scroll to the point where your item fits in the view.
I downloaded David's code and ran it two ways. Click the links to see the results.
1) with pixmap=pixmap.scaledToHeight(this->graphicsView->height());
2) with pixmap=pixmap.scaledToHeight(200);
I don't know enough to explain why this is happening, but I thought it would be a useful data point.
It turns out the problem was that the GraphicsView was in a layout. In my example, the resizing of the image was done in the Form constructor. Apparently this is before the layout takes its shape? I moved the code to a pushButton and when I click it the image is sized how I would expect.
I got the image to stay sized to the GraphicsView in the Layout by subclassing QGraphicsView and reimplementing :
class CustomGraphicsView: public QGraphicsView
{
Q_OBJECT
{
void resizeEvent ( QResizeEvent * event )
{
emit resized();
}
signals:
void resized();
}
Then I connect this resized() signal to a slot that simply calls this->View->fitInView (this->ImageToTraceItem);
David
I have a modal QDialog, that on the click of a button slides a modeless child QDialog out from underneath it. The problem I have is that the child stays on top of its parent during the animation.
I think I could get away with applying a mask over the portion of the child that overlaps the parent, but it feels like I'm missing a more obvious way of just placing the child under the parent.
I'm using Qt 4.5. Here's some sample code:
void MainWindow::on_myMenu_triggered()
{
parentDlg = new QDialog(this);
parentDlg->setFixedSize(250, 250);
parentDlg->setModal(true);
parentDlg->show();
childDlg = new QDialog(parentDlg);
childDlg->setFixedSize(150, 150);
childDlg->show();
QTimeLine* timeLine = new QTimeLine(1000, this);
connect(timeLine, SIGNAL(valueChanged(qreal)), this, SLOT(childDlgStepChanged(qreal)));
timeLine->start();
}
void MainWindow::childDlgStepChanged(qreal)
{
int parentX = parentDlg->frameGeometry().x();
int parentY = parentDlg->geometry().y();
// Move the child dialog to the left of its parent.
childDlg->move(parentX - 150 * step, parentY);
}
Thanks in advance.
Child widgets are always rendered over the parent so you would have to break that relationship in order to achieve the affect you are looking for directly. Then you could use raise() or lower() if both dialogs had the same parent.