I have a dialog with two buttons in the title bar: the context help button and the close button. How can I find out that the user clicked the context help button to perform my custom action? (I want to show some help page in the browser as in VS dialogs.)
I found a similar question, but how to do this with qt?
Context help button behaviour on CPropertySheet
Update.
Now I use the code like this:
class MyHelper : public QObject
{
Q_OBJECT
public:
explicit MyHelper( QObject * parent = nullptr ) {
qApp->installEventFilter( this );
}
protected:
virtual bool eventFilter( QObject * obj, QEvent * ev ) override {
if ( ev->type() == QEvent::EnterWhatsThisMode ) {
showHelp( QApplication::activeWindow() );
return true;
}
return QObject::eventFilter( obj, ev );
}
private:
void showHelp( QWidget * sender ) {
//TODO
}
};
I believe that QWidget::nativeEvent is what you are looking for.
Related
My goal is to retranslate a QObject subclass on the fly.
In QWidget it's really simple to catch QEvent::LanguageChange: we just override changeEvent. However, there is not such method in QObject and this is where I'm stuck.
How to catch QEvent::LanguageChange in QObject?
You can simply override the QObject::event method...
class my_object: public QObject {
using super = QObject;
protected:
virtual bool event (QEvent *event) override
{
if (event->type() == QEvent::LanguageChange) {
/*
* Retranslation code goes here...
*/
/*
* Return true to prevent further processing. This may
* or may not be what you want depending on your needs.
*/
return true;
}
/*
* Fall through to the base class implementation.
*/
return super::event(event);
}
};
Alternatively, you could put the same logic in an event filter and attach that to the QObject of interest.
I'm making a program where the user can add multiple people (participants) in a list. When the "Add" button is clicked, a new row is added and "edit" is called for the name field. All is well so far, but there is a thing I'd like to implement, and I can't seem to figure out how: when the user closes the editing field (presses enter or escape, clicks elsewhere, etc.) and if the name field remains empty, I'd like the row to be deleted. In other words, a name has to be filled in. Here is what I have so far:
void MainWindow::addParticipant()
{
QList<QStandardItem *> newRow;
newRow << new QStandardItem()
<< new QStandardItem();
participantModel->appendRow(newRow);
participantView->edit(participantModel->index(participantModel->rowCount()-1, 0));
}
Here participantModel is a QStandardItemModel and participantView is a QTreeView. I tried using signals and slots to detect when a row is empty and to delete it, but it hasn't worked and the syntax is elusive to me.
Ideally I'd be able to detect when the name field is not being edited anymore, so that I can delete the row if need be.
Here is ugly but working solution: subclass from QItemDelegate and check input data inside setModelData member function. As far setModelData has a const qualifier you can not modify model inside it, so you need some trick: in the following example the model is modified inside handler of closeEditor signal.
class MainWidget : public QWidget
{
Q_OBJECT
public:
MainWidget ()
{
QStandardItemModel * model = new QStandardItemModel ();
ItemDelegate * delegate = new ItemDelegate ();
table->setItemDelegate (delegate);
connect (delegate, & ItemDelegate::closeEditor, [=](){
if (isEmpty) {
model->removeRow (emptyRow);
isEmpty = false;
emptyRow = -1;
}
});
connect (delegate, & ItemDelegate::cellEdited, [=](const int row){
isEmpty = true;
emptyRow = row;
});
}
bool isEmpty;
int emptyRow;
};
class ItemDelegate : public QItemDelegate
{
Q_OBJECT
signals:
void cellEdited (int) const;
public:
void setModelData (QWidget * widget, QAbstractItemModel * model, const QModelIndex & index) const override
{
if (0 == index.column () ) {
if (QLineEdit * cellWidget = qobject_cast <QLineEdit *> (widget) ) {
if (cellWidget->text ().isEmpty () ) {
emit cellEdited (index.row () );
return;
}
}
}
QItemDelegate::setModelData (widget, model, index);
}
};
Complete example available at GitLab.
The comments/answers posted thus far have urged me to look more into item delegates. Quite embarrassingly, after relatively little googling I found the following solution for my problem:
void MainWindow::addParticipant()
{
QStyledItemDelegate *participantDelegate = new QStyledItemDelegate;
participantView->setItemDelegateForColumn(0, participantDelegate);
QList<QStandardItem *> newRow;
newRow << new QStandardItem()
<< new QStandardItem();
participantModel->appendRow(newRow);
connect(participantDelegate, SIGNAL(closeEditor(QWidget*,QAbstractItemDelegate::EndEditHint)), this, SLOT(checkRow()));
participantView->edit(participantModel->index(participantModel->rowCount()-1, 0));
}
Apparently the closeEditor signal (only available to delegates) is exactly what I was looking for. When the editor is closed, the slot checkRow() checks if the name field of the participant is empty and decides whether or not to delete the row.
I am using QMouseEvent and QKeyEvents in my program. I programmatically make various widgets (QDockWidgets and QCustomPlots).
I would like to use a single click and keypress handler function. However, I am struggling to get the widget that is actually being clicked, so that I can do certain stuff within that widget.
Is there a way to return from a ClickEvent the name of the widget that was clicked?
You can implement eventFilter in your mainWindow and listen for events from widgets there :
bool MainWindow::eventFilter(QObject * obj, QEvent * event)
{
if((myWidget *)obj == widget1 && event->type()==QEvent::KeyPress)
{
int pressedKey = ((QKeyEvent*)event)->key();
...
}
else if((myWidget *)obj == widget2 && event->type()==QEvent::MouseButtonRelease)
{
if(((QMouseEvent*)event)->button() == Qt::LeftButton)
{
...
}
}
return false;
}
Also do not forget to install event filters for your widgets in the mainWindow constructor :
widget1->installEventFilter(this);
widget2->installEventFilter(this);
How to make a QT dialog read-only? Any general way to implement it easily? For example
(1) set all its containing widgets disable. (how to implement it?)
(2) Intercept edit events like key pressed, mouse pressed but how not to intercept the one to close the dialog?
I think this feature should be very helpful.
Disabling the widgets can be done similar to the following:
void myDialog::disableWidgets()
{
QList<QWidget *> widgets = this->findChildren<QWidget *>();
foreach(QWidget* widget, widgets)
{
widget->setEnabled(false);
}
}
To intercept events, QDialog includes the function installEventFilter(QObject*).
This allows you to use a separate object to receive all events passed to the dialog. You can then choose to handle the event in the object, or pass it on to the dialog itself by calling the base class QObject::eventFilter
class MyEventHandler : public QObject
{
Q_OBJECT
protected:
bool MyEventHandler::eventFilter(QObject *obj, QEvent *event)
{
// handle key press events
if (event->type() == QEvent::KeyPress)
{
// Do something
// ...
return true; // event handled by the class
}
else
{ // ignore this event and pass it to the dialog as usual
return QObject::eventFilter(obj, event);
}
}
return false;
};
QDialog* dlg = new QDialog;
MyEventHandler evtHandler = new MyEventHandler;
dlg->installEventFilter(evtHandler);
Read-only is a strange term to apply to a dialog. Disabling all widgets as above does the trick. If you only wanted to make the input part of a QInputDialog read-only (while leaving scrollbars, buttons, etc. enabled), you could adapt that code as below:
QInputDialog dialog(this);
dialog.setOptions(QInputDialog::UsePlainTextEditForTextInput);
dialog.setWindowTitle("Title");
dialog.setLabelText("Label");
dialog.setTextValue("1\n2\n3\n");
QList<QWidget *> widgets = dialog.findChildren<QWidget *>();
foreach(QWidget* widget, widgets) {
if (strcmp(widget->metaObject()->className(),"QPlainTextEdit")==0) {
QPlainTextEdit *t = static_cast<QPlainTextEdit*>(widget);
t->setReadOnly(true);
}
}
dialog.exec();
In QT: I use a class inherited from QToolButton and rewrite event(QEvent*), now I want to add 'mousePressEvent', but it never gets hit, does event(QEvent*) conflict with mousePressEvent(QMouseEvent *) ? Thank you.
bool IconLabel::event (QEvent* e ) {
if ( e->type() == QEvent::Paint) {
return QToolButton::event(e);
}
return true;
}
void IconLabel::mousePressEvent(QMouseEvent* e)
{
int a = 1;//example
a = 2;// example//Handle the event
}
The class is:
class IconLabel : public QToolButton
{
Q_OBJECT
public:
explicit IconLabel(QWidget *parent = 0);
bool event (QEvent* e );
void mousePressEvent(QMouseEvent* e);
signals:
public slots:
};
All events received by a widget pass through event(..), and then are redirected to the appropriate event handler method. You have made the mistake of not forwarding on any events except paint events, if you just want to add mouse press event handling do this:
bool IconLabel::event (QEvent* e ) {
if ( e->type() == QEvent::Paint ||
e->type() == QEvent::QEvent::MouseButtonPress ) {
return QToolButton::event(e);
}
return true;
}
Also event handler methods should really be in protected, because events are only supposed to be distributed via the event queue (QCoreApplication::postEvent(..), etc.).