I catch the mouseMoveEvent of my QWebView for restarting a timer of a screensaver. The problem is that now the mouseMoveEvent isnt distribued to the HTML elements so its impossible for example to move a sliding bar on the page.
I use connect to bind mouseMoveEvent to the restart slot :
QObject::connect(_view, SIGNAL(mouseMoveEvent(QMouseEvent*)), _mediaPlayer, SLOT(stop()));
WebView class :
class WebView : public QWebView
{
Q_OBJECT
public:
WebView(QString menu) : _menuDesc(menu) {};
WebView(){};
void setMenuDesc(QString menu) {_menuDesc = menu;};
QString getMenuDesc() {return _menuDesc;};
void setCurrPage(QString page) {_currPage = page;};
QString getCurrPage() {return _currPage;};
void setCurrCategory(QString page) {_currPage = page;};
QString getCurrCategory() {return _currPage;};
void mouseMoveEvent(QMouseEvent *)
{
emit mouseMoved();
};
signals :
void mouseMoved();
private:
QString _menuDesc = 0;
QString _currPage;
QString _currCategory = 0;
};
Is there a solution to still catch the signal and pass it to the HTML page?
mouseMoveEvent is not a signal but an event handler. You can reimplement this event handler and let it emit a signal you can connect to if you need that.
Like this:
MyWebView::mouseMoveEvent(QMouseEvent * e) {
emit mouseMoved(); // this would be signal you could connect to.
}
Seems you misunderstand event handler and signal usages.
mouseMoveEvent is a member method of QWidget, is not a signal so you cannot connect to it. You can override it in you subclass and emit your own signal.
And if a QWidget's mouse tracking is switched off, mouse move events only occur if a mouse button is pressed while the mouse is being moved. Maybe you need to call setMouseTracking too.
Related
I am a beginner in Qt and I would like to know, how can I create an event which checks when a button in the windows gets clicked? The window has a single push button.
I could not find a simple and correct example for my question, that's why I am asking here. I did google first.
Thank you
class MyClass : public QWidget
{
public:
MyClass ()
{
QPushButton *pButton = new QPushButton(this);
QObject::connect(pButton, &QPushButton::clicked, this, &MyClass::onButtonClicked);
}
public slots:
void onButtonClicked () {qDebug () << "Button clicked";};
};
onButtonClicked will be called if the button pressed.
Please see signals & slots and QPushButton signals for more information.
Qt employs the signals and slots paradigm. You don't check if a button is clicked. When a button is clicked, it emits a signal. You can connect your own functions to that signal. So whenever that button is clicked, the signal is emitted, and triggers all the functions it is connected to.
Be sure to check out signals and slots, which is a core concept of Qt, along with properties and meta data.
Note that as a QWidget derived, a button comes with the following methods, which are triggered by mouse events and you can override them if you wish, although in the case of something as a button that is hardly necessary:
virtual void mouseDoubleClickEvent(QMouseEvent * event)
virtual void mouseMoveEvent(QMouseEvent * event)
virtual void mousePressEvent(QMouseEvent * event)
virtual void mouseReleaseEvent(QMouseEvent * event)
I am using Qt 5.7 (the latest version). I can't get the mouse events to work in QGraphicsScene, but they work in window outside of my scene. I have followed this question.
So I have overwritten QWidget::mouseMoveEvent() in my main widget's subclass like this:
// header:
class MyWidget {
...
void mouseMoveEvent( QMouseEvent * event );
};
// source:
MyWidget::MyWidget() {
setMouseTracking();
}
void MyWidget::mouseMoveEvent( QMouseEvent * event ) {
}
It doesn't work for: mouseMoveEvent, mouseGrabber, mousePressEvent, mouseReleaseEvent, or mouseDoubleClickEvent. But somehow it only works for mousePressEvent.
Could this be a bug in Qt?
SOURCE CODE:
In objectloader.cpp
ObjectLoader::ObjectLoader(QWidget *parent) :
QMainWindow(parent),
ui(new Ui::ObjectLoader)
{
ui->setupUi(this);
scene=new QGraphicsScene(this);
ui->graphicsView->setScene(scene);
ui->graphicsView->setMouseTracking(true);
setMouseTracking(true);
}
Thats were i set mouse tracking twice
In objectloader.h
Then i define that method in objectloader.h
class ObjectLoader : public QMainWindow
{
Q_OBJECT
public:
explicit ObjectLoader(QWidget *parent = 0);
~ObjectLoader();
private slots:
void mouseMoveEvent(QMouseEvent *event);
protected:
private:
};
#endif // OBJECTLOADER_H
And implementation of that method in objectloader.cpp
void ObjectLoader::mouseMoveEvent(QMouseEvent *event){
qDebug()<<"Mouse moved";
}
When a mouse event is generated by Qt it is generally passed initially to the QWidget that was under the mouse pointer when the event was generated. If that QWidget accepts the event then no further processing will take place. If the event isn't accepted then Qt may propogate the event to that QWidget's parent and so on.
In your particular case the mouse move events you are interested in are being sent to the QGraphicsView/QGraphicsScene conponents where they are being accepted and, hence, no further processing takes place. In a case like that you generally need to install an event filter to intercept and process the events of interest.
Mouse move events will occur only when a mouse button is pressed down, unless mouse tracking has been enabled with QWidget::setMouseTracking().
So, I think you should check whether mouseTracking is really enabled or not, by using `bool hasMouseTracking() const'.
In example code:
class MyWidget : public QWidget
{
Q_OBJECT
protected:
void mousePressEvent(QMouseEvent *event)
{
qDebug() << event;
event->accept();
QInputDialog::getText(NULL, "", "");
}
};
When I click Right mouse button on widget Input dialog appear on screen. After I click any button on dialog it closed and mousePressEvent call again and again and show dialog. If I click Left mouse button or Ctrl+Left Mouse button on widget all work fine.
This bug apper only on Mac OS (under Windows work fine).
Please help me to avoid this bug.
Those static/synchronous dialog functions always seemed a bit dubious to me -- they are implemented by recursively re-invoking the Qt event loop routine from within the getText() call, and so it's easy to get "interesting" re-entrancy issues when you use them. (For example, if some event in your program were to delete the MyWidget object before the user had dismissed the QInputDialog, then after QInputDialog::getText() returned, the program would be executing from within the mousePressEvent() method of a deleted MyWidget object, which is a situation that is just begging to cause undefined behavior)
In any case, my recommended fix is to avoid the static/synchronous getText() call and use signals instead, something like this:
#include <QWidget>
#include <QInputDialog>
#include <QMouseEvent>
class MyWidget : public QWidget
{
Q_OBJECT
public:
MyWidget() : dialog(NULL) {}
~MyWidget() {delete dialog;}
protected:
void mousePressEvent(QMouseEvent *event)
{
event->accept();
if (dialog)
{
dialog->raise();
dialog->setFocus();
}
else
{
dialog = new QInputDialog;
connect(dialog, SIGNAL(finished(int)), this, SLOT(dialogDismissed()));
dialog->show();
}
}
private slots:
void dialogDismissed()
{
if (dialog)
{
int result = dialog->result();
QString t = dialog->textValue();
printf("Dialog finished, result was %i, user entered text [%s]\n", result, t.toUtf8().constData());
dialog->deleteLater(); // can't just call delete because (dialog) is what is calling this function (via a signal)!
dialog = NULL;
}
}
private:
QInputDialog * dialog;
};
I'm implementing a class that inherits the QTreeWidget,
I'm trying to do something only when the user left-clicks on an item.
Since itemDoubleClicked only gives you the item and not the mouse event,
and mouseDoubleClickEvent only gives you the mouse event with no item,
so I thought I would add a member in the class and record whether left or right button was pressed in mouseDoubleClickEvent,
then check that info when entering the slot connected to signal itemDoubleClicked.
That is, if the signal is emitted after the event handler. I was planning on experimenting if this was true, but then I ran into this issue.
Ok, back to the class, it looks something like this:
class myTreeWidget : public QTreeWidget{
Q_OBJECT
private:
Qt::MouseButton m_button;
public:
myTreeWidget(QWidget* parent):QTreeWidget(parent){
m_button = Qt::NoButton;
connect(this, SIGNAL(itemDoubleClicked(QTreeWidgetItem*, int)),
this, SLOT(slot_doubleClick(QTreeWidgetItem*,int)));
}
void mouseDoubleClickEvent(QMouseEvent* event){
m_button = event->button();
}
public slots:
void slot_doubleClick(QTreeWidgetItem* item, int column);
signals:
void itemDoubleClicked(QTreeWidgetItem* item, int column);
}
Yep, something like this.
Then I used gdb to check which was called first,
mouseDoubleClickEvent or slot_doubleClick,
and it turns out that slot_doubleClick was not called at all.
I commented out mouseDoubleClickEvent and tried again,
and slot_doubleClick was called.
So um... what I'm asking here is...
is this a limitation in Qt?
Can I only choose one between signals&slots and event handlers?
Or am I just doing it wrong?
Moreover, if this is a limitation,
can you recommend another solution to what I'm trying to do?
(only respond to left double-clicks)
Sorry for the long post and thanks!
If you override some event handler and want also default behavior, you should call base handler implementation. For example try this:
void mouseDoubleClickEvent(QMouseEvent* event){
m_button = event->button();
QTreeWidget::mouseDoubleClickEvent(event);
}
I have a Qt app with a QGraphicsView and QGraphicsScene. I subclassed them both and want to handle mouseevents in both. I can do this for both classes separately, using
virtual void mousePressEvent(QMouseEvent* event);
But when I handle the events in the GraphicsView, I don't receive them anymore in the GraphicsScene. How do I fix this, i.e. pass the event from the grapchicsview to the graphicsscene?
Just forward mousePressEvent to your GraphicsView's parent, this will then call scene's mousePressEvent :
void MyGraphicsView::mousePressEvent(QMouseEvent * e)
{
// forward to scene (via default view behaviour)
QGraphicsView::mousePressEvent(e) ;
// ...
}
BTW, QGraphicsScene::mousePressEvent has a different kind (class) of event : QGraphicsSceneMouseEvent
Call the base implementation at the end of your overriden function, eg:
void MyView::mousePressEvent(QMouseEvent* event)
{
// do something
QGraphicsView::mousePressEvent(event);
}