I have a several QWidgets, let's say previewWidget, that each consist of 2 QLabels (maybe more and other than QLabel). I want to drag and drop previewWidgets across the main window.
Problem: I can move the widget by pressing the mouse on the green area, which is PreviewWidget area. However, if I try to drag the widget by clicking on one of the labels, that label moves out the previewWidget (sometimes I don't even understand what happens). What I want is to move a whole previewWidget or at least nothing to happen when a mouse is pressed on its children.
My approach. I overloaded mousePressEvent() as follows:
void MainWindow::mousePressEvent(QMouseEvent *event)
{
// I beleive my problem is right here...
PreviewWidget *child = static_cast<PreviewWidget*>(this->childAt(event->pos()));
if (!child)
return; // this is not returned even if the child is not of a PreviewWidget type
// Create QDrag object ...
}
How to drag and drop PreviewWidget the way I want? Any examples are appreciated.
I suggest a strategy for identifying the child at the cursor coordinates.
In your mousePressEvent:
//...
QWidget * child = childAt(e->pos());
if(child != 0)
{
QString classname(child->metaObject()->className());
if( classname == "QLabel")
{
child = child->parentWidget();
if(child != 0)
{
classname = child->metaObject()->className();
}
}
if(classname == "PreviewWidget")
{
//do whatever with child ...
}
}
Related
I have a QGraphicsView, which contains many rectangle and polylines. I wanted to print every object names ( every rectangle, polylines have names) once I clicked them on view through mouse click. I did that and worked perfectly.
But now I want to do that over mouse hovering. It means, if I hover a mouse over particular object, it should show its name besides cursor.
I tried that, but
I am not understanding, on hovering, how that particular object should get selected ?
And how to print its name besides cursor point ?
I tried this way:
bool myClass::eventFilter(QObject *watched, QEvent *event)
{
bool filterEvent = false;
switch(event->type())
{
case QEvent::MouseButtonPress:
{....}
case QEvent::MouseButtonRelease:
{...}
case QEvent::Enter:
{
QMouseEvent * mouseEvent = static_cast<QMouseEvent *>(event);
QPointF po = _view->mapToScene(mouseEvent->pos());
FindNamesOverHover(po);
}
return true;
default:
break;
}
return filterEvent;
}
void myClass::FindNamesOverHover(QPointF p)
{
QGraphicsRectItem* rItem = qgraphicsitem_cast<QGraphicsRectItem*>(_scene->itemAt(p,QTransform()));
if(rItem)
{
// some logic
qDebug()<< "Instance name is " << i->Name();
}
}
Constructor of class myClass
myClass::myClass(QWidget* parent) :
QDockWidget(parent)
{
scene = new QGraphicsScene(this);
view = new QGraphicsView(this);
view->setScene(_scene);
view->viewport()->installEventFilter(this);
}
Now above code works only,
When I select object through mouse click and then again hover over it.
Then it prints its name on console.
But I want only hovering ( no selection through mouse click) will show its name besides cursor point.
Can any one help me ?
You can override QGraphicsScene.mouseMoveEvent and inside it use QGraphicsScene.itemAt to query for item under cursor. To display you can use QGraphicsTextItem, just move it to correct position and apply text.
I have a subclass of QGraphicsView that should accept two kinds of mouse events: drag and drop for scrolling and simple clicks for item selection/highlight.
So I use
setDragMode(QGraphicsView::ScrollHandDrag);
to enable scrolling the view with the "Hand". And I have a function like this:
void GraphView::mouseReleaseEvent(QMouseEvent* e)
{
if (e->button() == Qt::LeftButton)
emit leftClicked(mapToScene(e->pos()));
else
emit rightClicked(mapToScene(e->pos()));
QGraphicsView::mouseReleaseEvent(e);
}
which creates signal whenever the user clicks on the scene.
However, the problem is: when I stop dragging and release the mouse button, the mouseReleaseEvent function is called, and if the cursor happens to be over some element of the scene, it will get highlighted.
How can I changed the mouseReleaseEvent function so that the signals are created only if there was no previous drag of the mouse?
If you use mousePress and mouseMove in combination with mouseRelease, then you can determine what mouse action the user just performed.
If you have mousePress then mouseRelease, then it must be a simple click.
If you have mousePress, mouseMove, and then mouseRelease, then it must be a drag.
The Qt documentation contains an example of interpreting combinations of mouse events in action in a scribbling program.
http://doc.qt.io/qt-4.8/qt-widgets-scribble-example.html
You can extend the principle to something like this:
private bool MyWidget::dragging = false;
private bool MyWidget::pressed = false;
void MyWidget::mousePressEvent(QMouseEvent *event)
{
if (event->button() == Qt::LeftButton) {
pressed=true;
}
QGraphicsView::mousePressEvent(event)
}
void MyWidget::mouseMoveEvent(QMouseEvent *event)
{
if ((event->buttons() & Qt::LeftButton) && pressed)
{
dragging=true;
}
QGraphicsView::mouseMoveEvent(event)
}
void MyWidget::mouseReleaseEvent(QMouseEvent *event)
{
if (event->button() == Qt::LeftButton && pressed) {
pressed = false;
if (dragging)
{
dragging = false;
}
else
{
// plain mouse click
// do something here
}
}
QGraphicsView::mouseReleaseEvent(event)
}
Note that this does not address edge cases where a user's mouse action is performed only partially inside the widget. I must also admit that I am relatively new to Qt and have not yet used ScrollHandDrag, but this is how one would go about identifying a certain combination of mouse events.
I've created a label and used setPixmap to attach a .png image to the label. I've also setWindowFlags to disable the title bar and create a frameless window. Because I've disabled those, it also disables the ability to drag anything around, so I want to create mouseevents (unless there's a better method) to position my label anywhere on the screen exactly like dragging the frame of a window. How would I do that? An example and brief explanation would be greatly appreciated.
reimplement the QMouseEvents you need .... like
void MyLabel::mousePressEvent(QMouseEvent* e)
{
m_moveDatWidget = true;
// so when the mousebutton got pressed, you set something to
// tell your code to move the widget ... consider maybe you
// want to move it only on right button pressed ...
}
void MyLabel::mouseReleaseEvent(QMouseEvent* e)
{
m_moveDatWidget = false;
// after releasing do not forget to reset the movement variable
}
void MyLabel::mouseMoveEvent(QMouseEvent* e)
{
// when in 'moving state' ...
if (m_moveDatWidget)
{
// move your widget around using QWidget::move(qreal,qreal)
}
}
this is only a really basic implementation but it should do well if you calculate the desired movement correct :)
I would implement the label dragging by mouse in the following way:
class Label : public QLabel
{
public:
// Implement the constructor(s)
protected:
void Label::mouseMoveEvent(QMouseEvent* event)
{
if (!m_offset.isNull()) {
move(event->globalPos() - m_offset);
}
QLabel::mouseMoveEvent(event);
}
void Label::mousePressEvent(QMouseEvent* event)
{
// Get the mouse offset in the label's coordinates system.
m_offset = event->globalPos() - pos();
QLabel::mousePressEvent(event);
}
void Notifier::mouseReleaseEvent(QMouseEvent* event)
{
m_offset = QPoint();
QLabel::mouseReleaseEvent(event);
}
private:
// The mouse pointer offset from the top left corner of the label.
QPoint m_offset;
};
I have a QGraphicsView window on my widget and have just put in an event for mouse wheel which zooms in on the image.
However as soon as i zoom in scroll bars are displayed and the scroll functionality on the mouse wheel overrides the zoom function i have.
i was wondering if there is any way that i can remove scrolling all together and add a drag to move option or maybe a CTRL and mouse wheel to zoom and mouse wheel alone would control scrolling
here is my zoom function (Which im aware isnt perfect) but if anyone could shed some light on that it would be a bonus
cheers in advance
void Test::wheelEvent(QWheelEvent *event)
{
if(event->delta() > 0)
{
ui->graphicsView->scale(2,2);
}
else
{
ui->graphicsView->scale(0.5,0.5);
}
}
You reimplemented wheelEvent for QWidget/QMainWindow that contains your QGraphicsView, however, wheelEvent of QGraphicsView remains intact.
You can derive from QGraphicsView, reimplement wheelEvent for derived class and use derive class instead of QGraphicsView - this way you won't even need wheelEvent in your QWidget/QMainWindow, and you can customize reimplemented wheelEvent to do what you want. Something like that:
Header file:
class myQGraphicsView : public QGraphicsView
{
public:
myQGraphicsView(QWidget * parent = nullptr);
myQGraphicsView(QGraphicsScene * scene, QWidget * parent = nullptr);
protected:
virtual void wheelEvent(QWheelEvent * event);
};
Source file:
myQGraphicsView::myQGraphicsView(QWidget * parent)
: QGraphicsView(parent) {}
myQGraphicsView::myQGraphicsView(QGraphicsScene * scene, QWidget * parent)
: QGraphicsView(scene, parent) {}
void myQGraphicsView::wheelEvent(QWheelEvent * event)
{
// your functionality, for example:
// if ctrl pressed, use original functionality
if (event->modifiers() & Qt::ControlModifier)
{
QGraphicsView::wheelEvent(event);
}
// otherwise, do yours
else
{
if (event->delta() > 0)
{
scale(2, 2);
}
else
{
scale(0.5, 0.5);
}
}
}
Scrolling can be disabled with the following code:
ui->graphicsView->verticalScrollBar()->blockSignals(true);
ui->graphicsView->setVerticalScrollBarPolicy(Qt::ScrollBarAlwaysOff);
ui->graphicsView->horizontalScrollBar()->blockSignals(true);
ui->graphicsView->setHorizontalScrollBarPolicy(Qt::ScrollBarAlwaysOff);
I think your question has a bit simpler answer.. To disable scroll bars just set scroll bar policy (QGraphicsView is just QScrollView), so step 1)
setVerticalScrollBarPolicy(Qt::ScrollBarAlwaysOff);
setHorizontalScrollBarPolicy(Qt::ScrollBarAlwaysOff);
that will disable scroll bars..
step 2) (if you want to keep it simple)
QGraphicsView * pView; // pointer to your graphics view
pView->setInteractive(true);
pView->setDragMode(QGraphicsView::ScrollHandDrag);
thats the fastest way to get results you want
I open QDialog window from QMainWindow. Now when I press the QDialog window
its not always closing in the first press - I need to press few times (3-4) to close it .
I have closeEvent slot that has simple event->accept(); inside it.
This is how I call the QDialog from the main window:
void MyManager::DialogContainerOpen(type t)
{
if(pMyDialogContainer == NULL)
{
pMyDialogContainer = new MyDialogContainer();
}
int returnVal = QDialog::Rejected;
if(!m_bContainer)
{
m_bContainer = true;
int returnVal = pMyDialogContainer->exec();
if(returnVal != QDialog::Accepted ) {
m_bContainer = false;
}
}
}
This is the first problem.
The second problem is how do i set the QDialog windows NOT to be allays on top? (I don’t want it to block the parent window.
UPDATE
well i found out that the function from the MainWindow that showing the contexMenu
and inside it has the connect single/slot is keeps to invoke so i just used the disconnect
i dont know if its the best sulotion but its working.
now i juat have the final problem .
here is the code i hope its ok
void MainWindowContainer::ShowContextMenu(const QPoint& pos) // this is a slot
{
QModelIndex modelIndx;
QPoint globalPos = ui.treeView_mainwindow->mapToGlobal(pos);
bool b1 = connect(OpenAction, SIGNAL(triggered()),m_SignalMapper, SLOT(map()) );
m_SignalMapper->setMapping(OpenAction,voidID);
bool b2 = connect(m_SignalMapper, SIGNAL(mapped(QString)), this, SLOT(OpenWin(QString)));
QAction* selectedItem = ContextMenu.exec(globalPos);
}
void MainWindowContainer::OpenWin(QString gid)
{
//disconnect(sender0, SIGNAL(overflow()),receiver1, SLOT(handleMathError()));
disconnect(m_SignalMapper, SIGNAL(mapped(QString)),this, SLOT(OpenWin(QString)));
disconnect(OpenAction,SIGNAL(triggered()),m_SignalMapper, SLOT(map()));
....
....
}
For your second question, the term you are looking for is modal vs modeless dialogs. The QDialog documentation tells exactly how you create non-modal dialogs:
Modeless dialogs are displayed using show(), which returns control to the caller immediately.
i.e. don't use exec() as that will make a modal dialog (which blocks the parent).
You should not connect the same signal/slot more than once unless you want the action run multiple times. All you need to do is to connect the QAction's signal to the slot once. This is usually done in the constructor (or a dedicated function called from the constructor) where you create the action.