Context menu on custom shortcut - c++

I have a QGraphicsView in my MainWindow and I have a custom "grab" function on my canvas (which is the QGraphicsView inside my MainWindow) called when I press both mouse buttons.
So I want to activate my context menu only when I press CTRL + right click and prevent from activating only with a right click. It would be important to keep ActionsContextMenu policy.
Is there a way to do that?

Just check for KeyboardModifier. You can specify which modifier you want. In your case, it is the ControlModifier. Then, override the method mousePressEvent() :
void yourClass::mousePressEvent(QMouseEvent *event)
{
if (event->button() == Qt::RightButton &&
event->modifiers() == Qt::ControlModifier)
{
// call your context menu
}
}
If you want to use this, you'll need to call a QMenu. Just add this function in your class :
void yourClass::showMenu()
{
QMenu contextMenu(this);
QAction action("My Action", this);
contextMenu.addAction(&action);
contextMenu.exec();
}

Related

How to create Mouse right click menu option using eventFilter in Qt?

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

Qt: accept mouseRelease only when there was no drag and drop

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.

Right click on QTreeView item

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

Automatically populate "Edit" menu in menubar with current focus widget context menu

I've been looking for ways to implement the "Edit" menu of Qt application. The "Edit" menu contains items such as "Copy", "Cut", "Paste", etc. and which need to forward to the currently active widget.
I can't seem to find a standard or elegant way to do this. According to this question, it's not possible:
How to implement the "Edit" menu with "Undo", "Cut", "Paste" and "Copy"?
I recently had the idea to trigger a context menu event on the current active widget when the "Edit" menu is shown, via:
// create menus in MainWindow constructor
...
edit_menu = menuBar()->addMenu(tr("&Edit"));
connect(edit_menu, SIGNAL(aboutToShow()), this, SLOT(showEditMenu()));
...
// custom slot to handle the edit menu
void MainWindow::showEditMenu()
{
QWidget* w = QApplication::focusWidget();
// show the context menu of current focus widget in the menubar spot
QPoint global_pos = edit_menu->mapToGlobal(edit_menu->rect().bottomLeft());
QPoint pos = w->mapFromGlobal(global_pos);
QApplication::sendEvent(w, new QContextMenuEvent(QContextMenuEvent::Keyboard, pos, global_pos));
}
This shows the a context menu for the current widget great, but has some problems. For example, it takes focus away from the menubar, or if you click a different menubar item first, the menubar has focus, etc.
One partial solution would be to grab the context menu from the widget and copy it's items into the edit menu dynamically. Is there a way to do this?
Is there a better way build the edit menu in Qt?
Thanks for your help.
well, if you just need to create menu, you can always take actions from actions of a widget. To create edit actions for widgets, you can do something like this:
void MainWindow::addActions (QWidget* widget)
{
QAction * copyAction = new QAction("copy",widget);
if(connect(copyAction,SIGNAL(triggered()),widget,SLOT(copy())))
{
widget->addAction(copyAction);
qDebug()<<"success connection";
}
}
and
foreach (QObject * obj, centralWidget()->children())
{
QWidget * w = dynamic_cast<QWidget*>(obj);
if (w)
addActions(w);
}
then you always can update actions of edit menu with focused widget's actions
This may be not elegant, but it better, than imporssible. The main bad assumption in example is that copy slot is named copy
An elegant solution I guess would be to have a base class for the widgets you need to have copy/paste/... functionality, and have them register themselves with some parent class upon becoming active and unregistering when being deactivated. The actions can then just be connected to slots in the main window, which forwards them to the registered widget. You could even gray out the menu items if no widget is currently registered (e.g. because the active widget does not have the required functionality).
An example for registering/unregistering (untested):
class ActionWidget;
class ActionWidgetManager
{
public:
ActionWidgetManager() : actionWidget_(0){}
void registerWidget(ActionWidget* widget){ actionWidget_ = widget; }
void unregisterWidget(ActionWidget* widget)
{ if (actionWidget_ == widget) actionWidget_ = 0; }
bool hasActiveWidget() const{ return actionWidget_ != 0; }
ActionWidget* getActiveWidget(){ return actionWidget_; }
private:
ActionWidget* actionWidget_;
};
class ActionWidget : public QWidget
{
public:
ActionWidget(ActionWidgetManager* manager, QWidget* parent=0)
: manager_(manager), QWidget(parent) {}
~ActionWidget(){ manager_->unregisterWidget(this); }
void Widget::changeEvent(QEvent *event)
{
QWidget::changeEvent(event);
if(event->type() == QEvent::ActivationChange){
if(isActiveWindow()) {
manager_->registerWidget(this);
}
else {
manager_->unregisterWidget(this);
}
}
}
virtual void doCopy() = 0;
virtual void doPaste() = 0;
virtual void doUndo() = 0;
virtual void doCut() = 0;
private:
ActionWidgetManager* manager_;
};
Or something equivalent using signals and slots.

QDialog not closing right away when pressing the X, how to make it NOT on top?

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.