I promote my QLineEdit to a custom widget and trying to reimplement mouse event handlers. I need to handle all mouse events except mouseDoubleClickEvent() by parent of my QLineEdit-based widget (parent is a custom scrollable area). All works well except wheelEvent(). QLineEdit is still handle mouse wheel and parent is still not.
Here is my promoted QLineEdit:
HeightLineEdit::HeightLineEdit(QWidget* parent) :
QLineEdit(parent)
{
this->setFocusPolicy(Qt::NoFocus);
}
void HeightLineEdit::mousePressEvent(QMouseEvent* event)
{
event->ignore();
}
void HeightLineEdit::mouseMoveEvent(QMouseEvent* event)
{
event->ignore();
}
void HeightLineEdit::mouseReleaseEvent(QMouseEvent* event)
{
event->ignore();
}
void HeightLineEdit::mouseDoubleClickEvent(QMouseEvent* event)
{
this->setFocus();
this->selectAll();
}
void HeightLineEdit::wheelEvent(QWheelEvent* event)
{
event->ignore();
}
From the QWheelEvent documentation: "Wheel events are sent to the widget under the mouse cursor, but if that widget does not handle the event they are sent to the focus widget."
If you want the parent to handle them for the child widget, you can either install an event filter on the child widget, or you could directly call a method on the parent widget from the child's wheelEvent method.
Related
I have a QGraphicsView which contains many QGraphicsItem. If I click mouse right click on any QGraphicsItem, the item should get select and right menu options should appear and then I will choose one of the options among them.To do that I have installed eventFilter and through it, I am using ContextMenu to create right click menu. Right click menu are getting cretaed properly. But propblem is I am not getting how to connect them to some function so that I can write logic for it.
It means if I clicked on save option that particular QGraphicsItem should get select and I should be able to go to some function where I will write logic for saving.
bool myClass::eventFilter(QObject *watched, QEvent *event)
{
switch(event->type())
{
case QEvent::ContextMenu:
{
QMouseEvent *mouseEvent = static_cast<QMouseEvent*> (event);
menu = new QMenu(this);
option = menu->addMenu("CopyOption");
option->addAction("save");
menu->exec(mouseEvent->globalPos());
break;
}
default:
break;
}
}
In your approach you show a context menu when you have no information if any item is selected. It is rather bad idea. You don't want to show the context menu in any location of view. You have to check if a cursor mouse is over an item.
Why not to derive from QGraphicsItem and just overload mousePressEvent method. Inside this method check if right button of mouse is clicked. If so, show context menu and test which action is clicked. Minimal code would be:
class TItem : public QGraphicsItem
{
bool _selected = false;
public:
TItem(QGraphicsItem* parent = nullptr) : QGraphicsItem(parent) {}
QRectF boundingRect() const override { return QRectF(0,0,20,20); }
void paint(QPainter *painter, const QStyleOptionGraphicsItem *option, QWidget *widget) override {
painter->fillRect(QRectF(0,0,20,20),_selected ? QColor(0,255,255) : QColor(255,255,0));
}
void mousePressEvent(QGraphicsSceneMouseEvent* e) override {
QGraphicsItem::mousePressEvent(e);
if (e->button() & Qt::RightButton) {
QMenu menu;
QAction* a1 = menu.addAction(QString("test1"));
QAction* a2 = menu.addAction(QString("test2"));
if(a2 == menu.exec(e->screenPos())) {
test2();
_selected = true;
update();
}
}
}
void test2() {
QMessageBox::information(nullptr,"test2","test2");
}
};
All the job with checking is an item is under mouse is done by QT, mousePressEvent is invoked only if it is necessary.
Another approach would be override mousePressEvent on QGraphicsView. Inside which:
get all items belonging to the scene
iterate over them, checking if an item is under mouse -> QGraphicsItem has isUnderMouse method
if any item is under mouse, create QMenu and show it
check selected QAction, if it is save call a proper method which doing the save and mark the item as selected
I have a QGraphicsView inside the MainWindow that has implemented a QGraphicScene. I need to pop up a widget when I right click the mouse on a certain portion of the QGraphicScene. The parent of the widget needs to be MainWindow.
My problem is that I need to verify the validity of the portion on witch I clicked inside a mousePressEvent in QGraphicScene and to pop up the widget at the exact same location but the coordinates of the QGraphicScene and MainWindow are obvious not the same. For that I use a custom signal that trigger a slot inside MainWindow and get the coordinates from the mousePressEvent of the MainWindow. The problem is that the mouseEvent from the QGraphicsScene is triggered before the mouseEvent from MainWindow. This makes perfect sense and works if I right click twice but I need it to work from the first right click.
I can not implement a filter or change the focus because I have tons of events in the application.
QGraphicScene:
void CGraphicScene :: mousePressEvent(QGraphicsSceneMouseEvent *event)
{
if(event -> button() == Qt::RightButton)
{
//test stuff
emit signalChangeContextualMenuPosition();
m_contextualMenu -> show();
}
}
MainWindow:
CGraphicScene *scene;
CContextualMenu *m_contextualMenu;
m_contextualMenu = new CContextualMenu(this);
m_contextualMenu ->close();
scene = new CGraphicScene(m_contextualMenu);
ui->gvInterface -> setScene(scene);
connect(scene, SIGNAL(signalChangeContextualMenuPosition()), this, SLOT(openPopUp()));
void MainWindow :: openPopUp()
{
m_contextualMenu ->move(m_xCoordPopMenu, m_yCoordPopMenu);
}
void MainWindow :: mousePressEvent(QMouseEvent *event)
{
if(event -> button() == Qt::RightButton)
{
m_xCoordPopMenu = event -> x();
m_yCoordPopMenu = event -> y();
}
}
Use the QGraphicsView::mapFromScene() to map scene coordinates to the view widget coordinates and then QWidget::mapToParent() to map the coordinates to it's parent widget, which is probably your main window. You can also find useful the method QWidget::mapTo().
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 want to generate the right click menu from the entry of a QTreeView. Currently I tried this, but I don't want the whole treeView to generate the right click and then me to filter the position on which the mouse is. I want that the signal to be generated from the entry.
connect(mtreeView, SIGNAL(customContextMenuRequested(const QPoint&)),
this, SLOT(showContextMenu(const QPoint&)));
Thanks!
Method 1
It is better to use the ContextMenuEvent rather than MouseReleaseEvent as it is a more portable way to trigger the context menu, will support accessibility on certain platforms, etc... The right click is not the only way to open a context menu.
If you do not want to subclass QTreeView , install an event handler from the main window:
ui->myTreeView->installEventFilter(this);
Then handle the event in the main window filterEvent
bool MainWindow::eventFilter(QObject *target, QEvent *event)
{
if (target == ui->myTreeView)
{
QContextMenuEvent* m = dynamic_cast<QContextMenuEvent*>(event);
if (event->type() == QEvent::ContextMenu && e!=0)
{
//Create context menu here
return true;
}
}
return false;
}
Method 2
Change the context menu mode to a signal:
ui->myTreeView->setContextMenuPolicy(Qt::CustomContextMenu);
connect(ui->myTreeView, SIGNAL(customContextMenuRequested(QPoint)),
this, SLOT(treeCustomMenu(QPoint)));
Then implement your slot:
void MainWindow::treeCustomMenu(const QPoint & pos)
{
//Implement your menu here using myTreeView->itemAt(pos);
}
What I do is to override mouseReleaseEvent and check manually.
void MyTreeView::mouseReleaseEvent(QMouseEvent *e) {
if (e->button() == Qt::RightButton) {
QTreeWidgetItem *item = itemAt(e->pos());
if (item) {
QMenu m;
m.addAction("hello");
m.addAction("world");
QAction *selected = m.exec(mapToGlobal(e->pos()));
if (selected) {
qDebug() << "selected" << selected->text();
}
}
} else {
QTreeView::mouseReleaseEvent(e);
}
}
What you mean by the entry is not represented by a QObject in Qt. Only the item model is a QObject, but the individual tree nodes are not QObjects in Qt item/view system.
Therefore, they cannot emit any signal
I have a QListWidget on a dialog that I want to do something (for example, open a QFileDialog window) when a user double-clicks on the QListWidget. Unfortunately, the void doubleClicked (const QModelIndex & index) only fires when there are items in the list.
Is it possible to get the widget to fire the signal whenever a double-click event is received, anywhere within the widget? Or is a different approach required?
You can install an event filter to the listwidget's viewport widget, something like this:
listWidget->viewport()->installEventFilter(this); // "this" could be your window object.
In the eventFilter method check for the QEvent::MouseButtonDblClick event:
bool YourWindowClass::eventFilter(QObject *obj, QEvent *event)
{
if (event->type() == QEvent::MouseButtonDblClick)
{
QMouseEvent *mouseEvent = static_cast<QMouseEvent*>(event);
qDebug("Mouse double click %d %d", mouseEvent->x(), mouseEvent->y());
return true;
}
else
{
return QMainWindow::eventFilter(obj, event);
}
}
I hope this helps.