I'm trying to find out whether a button is being pressed or not from within the paintEvent(), so that I can draw the "down" state. However, I don't know where to find this information. I tried QStyleOptionButton::state but it doesn't tell whether the button is being clicked or not.
The output of the debug statement is always something like "QStyle::State( "Active | Enabled | HasFocus | MouseOver" )" so nothing about a MouseDown state.
void XQPushButton::mousePressEvent(QMouseEvent* event) {
QPushButton::mousePressEvent(event);
QStyleOptionButton options;
options.initFrom(this);
qDebug() << (options.state);
}
void XQPushButton::paintEvent(QPaintEvent* event) {
QPushButton::paintEvent(event);
QStyleOptionButton options;
options.initFrom(this);
qDebug() << (options.state);
}
So any idea how I can detect if the button is being clicked?
QPushButton inherits QAbstractButton, which provides the down property:
This property holds whether the button is pressed down.
The documentation of the QStyleOption parent class contains an example that uses this property:
void MyPushButton::paintEvent(QPaintEvent *)
{
QStyleOptionButton option;
option.initFrom(this);
option.state = isDown() ? QStyle::State_Sunken : QStyle::State_Raised;
//...
}
In other words, the sunken/raised state is not initialized by initFrom(). This makes some sense, since initFrom is inherited from QStyleOption and takes a QWidget:
void initFrom ( const QWidget * widget )
– and a generic QWidget has no notion of "raised" or "sunken".
At least this is how I read the docs.
Related
I've Dialog that shows folders (in treeView) and files (in listView) respectively. In listView doubleClick signal is handled by a slot that Qt created while I used Designer with aproppriate slot to be implemented. The problem is that I'm not able to handle RIGHT MOUSE click. Is there a solution?
P.S.
I've googled for a while to solve this problem, it seems that inheriting QListView and overriding solve the problem. But in my case I've already populated Qt's standart QListView using Designer.
In this case you can use event filter:
bool MainWindow::eventFilter(QObject *obj, QEvent *event)
{
if (obj == ui->listView->viewport() && event->type() == QEvent::MouseButtonDblClick)
{
QMouseEvent *ev = static_cast<QMouseEvent *>(event);
if (ev->buttons() & Qt::RightButton)
{
qDebug()<< "double clicked" << ev->pos();
qDebug()<< ui->listView->indexAt(ev->pos()).data();
}
}
return QObject::eventFilter(obj, event);
}
To use eventFilter you should also:
protected:
bool eventFilter(QObject *obj, QEvent *event);//in header
and
qApp->installEventFilter(this);//in constructor
Possible addition to your problem. If you want do different things when user clicks left or right mouse buttons you should handle lest and right clicks in filter, without doubleClick signal (because it emits signal in both cases) and your code can be something like:
QMouseEvent *ev = static_cast<QMouseEvent *>(event);
if (ev->buttons() & Qt::RightButton)
{
qDebug()<< "RightButton double clicked";
//do something
}
if (ev->buttons() & Qt::LeftButton)
{
qDebug()<< "LeftButton double clicked";
//do something
}
In my case, I started trying to catch mouse events when a user right-clicked on a line in the QListView, but they never came through. However, all I really wanted to do was popup a context menu, and it turns out the contextMenuEvent did get through! So I didn't have to subclass QListView, just added a contextMenuEvent() to my widget that contained the QListView.
This was Qt3, so your mileage will most definitely differ.
For example, consider a main menu item that has the Delete key as a shortcut (with Qt::WindowShortcut as context). I want another QWidget to handle the Delete key when focused. This is not possible because the Delete key is processed by the main menu. I've tried grabbing the keyboard on QWidget focus but that doesn't do anything. Is this event possible?
I was able to get the behavior I wanted by installing an event filter on qApp when the QWidget is focused (remove it when losing focus), and returning true for all QEvent::Shortcut types.
void MyWidget::focusInEvent( QFocusEvent *event )
{
qApp->installEventFilter(this);
}
void MyWidget::focusOutEvent( QFocusEvent *event )
{
qApp->removeEventFilter(this);
}
bool MyWidget::eventFilter( QObject *target, QEvent *event )
{
if (event->type() == QEvent::Shortcut)
{
// If I care about this shortcut, then return true to intercept
// Else, return false to let the application process it
}
return false;
}
If there's a better way, I'd love to hear it!
In a dialog, when the tab key is pressed, the focus changes to another widget. In Qt, is there any signal for when a widget loses its focus? Can I use it to check if the input is valid or not? If not, can I set the focus back and ask the user to re-input?
There's no signal but if you want to know when your widget has lost focus, override and reimplement void QWidget::focusOutEvent(QFocusEvent* event) in your widget. It will be called whenever your widget has lost focus. To give focus to a widget, use QWidget::setFocus(Qt::FocusReason).
To validate input in a QLineEdit or QComboBox you can subclass QValidator and implement your own validator, or use one of the existing subclasses, QIntValidator, QDoubleValidator, or QRegExpValidator. Set the validator with QLineEdit::setValidator(const QValidator*) and QComboBox::setValidator(const QValidator*) respectively.
If you want to validate the contents of a modal dialog box, one way would be to override QDialog::exec() with an implementation like this:
int MyDialog::exec() {
while (true) {
if (QDialog::exec() == QDialog::Rejected) {
return QDialog::Rejected;
}
if (validate()) {
return QDialog::Accepted;
}
}
}
bool MyDialog::validate() {
if (lineEdit->text().isEmpty()) {
QMessageBox::critical(this, "Invalid value", "The specified value is not valid");
lineEdit->setFocus();
lineEdit->selectAll();
return false;
}
return true;
}
It will not allow the user to close the dialog with the OK button or any other button with the Accepted role unless the contents of the dialog is successfully validated. In this example I assume the dialog has a QLineEdit named lineEdit and the validate function will make sure that its content is not empty. If it is, it will set the focus to the QLineEdit and show the dialog again.
It is also possible (and easier) to create the signal yourself
In the .cpp (do not forget to include the moc)
class FocusWatcher : public QObject
{
Q_OBJECT
public:
explicit FocusWatcher(QObject* parent = nullptr) : QObject(parent)
{
if (parent)
parent->installEventFilter(this);
}
virtual bool eventFilter(QObject *obj, QEvent *event) override
{
Q_UNUSED(obj)
if (event->type() == QEvent::FocusIn)
emit focusChanged(true);
else if (event->type() == QEvent::FocusOut)
emit focusChanged(false);
return false;
}
Q_SIGNALS:
void focusChanged(bool in);
};
And to connect it:
connect(new FocusWatcher(myWidget), &FocusWatcher::focusChanged, this, &View::doSomething);
I would like to open a window when I click on a QSpinBox. The problem is that there is no such signal "clicked" for this widget.
Does someone has an idea how to do that?
A QSpinBox is just a QLineEdit with two buttons, input validation and event handling. It doesn't have clicked signal because it's supposed to handle the mouse even itself.
The problem is that even making a custom widget derived from QSpinBox won't be enough since it doesn't receive the mouse events itself, they are handled by its children widgets. You could install an event filter on the QSpinBox children in order to catch the click event, but that's not the neatest way.
If you just want to display a numpad when the user select the box, you can use directly a QLineEdit. You will lose the QSpinBox buttons (but you can add your own ones if you need them) and the validation (but you can add you own using QValidator).
Then you just have to derive it in order to catch the focus event, trigger a custom signal which would show your keyboard :
class MySpinBox: public QLineEdit
{
Q_OBJECT
public:
MySpinBox(QWidget *parent = 0);
~MySpinBox();
signals:
needNumpad(bool hasFocus);
protected:
virtual void focusInEvent(QFocusEvent *e) {
QLineEdit::focusInEvent(e);
emit(needNumpad(true));
}
virtual void focusOutEvent(QFocusEvent *e) {
QLineEdit::focusInEvent(e);
emit(needNumpad(false));
}
}
You can use an event filter and do something like this:
ui->spinBox->installEventFilter(this);
QObjectList o_list = ui->spinBox->children();
for(int i = 0; i < o_list.length(); i++)
{
QLineEdit *cast = qobject_cast<QLineEdit*>(o_list[i]);
if(cast)
cast->installEventFilter(this);
}
And in the event filter you check for a mouse click (in this example its triggered by all mouse buttons, left click, right click, scroll wheel click etc.).
bool MainWindow::eventFilter(QObject *obj, QEvent *event)
{
if(event->type() == QEvent::MouseButtonPress)
{
showNumpadDialog();
}
return false;
}
You do not need to create your own QSpinBox with QLineEdit and two buttons.
Since QLineEdit is the child of QSpinBox. You can create an event filter for QLineEdit and check whether its parent is a spinbox. Then so, you would get a click event for spin box.
if(event->type() == QEvent::MouseButtonPress && dynamic_cast<QSpinBox *>(dynamic_cast<QLineEdit *>(obj)->parent()) )
When I set flags of QAbstractItemModel selectable but not enabled, I can't select items by mouse click. However internally select() function selects objects.
Is this qt bug, or I do something wrong?
From what I understood, you want to "Disable" the item, but at the same time, be able to select it. it's fairly easy to fake that on the model.
if ( role == Qt::BackgroundRole ){
return QVariant(QApplication::palette()->color(QPalette::Inactive, QPalette::Window );
}
This will paint your item as grayed out, and you will still be able to select it.
You're doing something wrong. If you disable a widget it is greyed out and it doesn't receive user mouse clicks and keyboard input.
I just had similar problem (I need to copy disabled items). Here is solution that sets correct style for disabled items (without ignoring any style sheets).
Create custom item delegate for your model.
/// Returns false only if item needs to be rendered as disabled.
bool isIndexEnabled(const QModelIndex &index)
{
// Implement this function.
}
class ItemDelegate : public QStyledItemDelegate {
public:
explicit ItemDelegate(QObject *parent = nullptr)
: QStyledItemDelegate(parent) {}
protected:
void initStyleOption(
QStyleOptionItemView *option, const QModelIndex &index) const override
{
QStyledItemDelegate::initStyleOption(option, index);
if (!isIndexEnabled(index))
option->state &= ~QStyle::State_Enabled;
}
};
Set the new item delegate to your model.
auto itemDelegate = new ItemDelegate(model)
model->setItemDelegate(itemDelegate);