I am trying to build an application that after getting some user input on the first window, pops up another window and displays some results. However, even though the menubar is visible on the first window, the menubar does not appear on the second window. The two windows are objects of different classes, but both classes are inherited from QMainWindow.
I have tried using the menuBar() function which returns a pointer for the menubar to add menus (this works for the first window). I also tried creating a new menubar object which didn't help either.
//MapWindow.h
class MapWindow : public QMainWindow
{
Q_OBJECT
public:
explicit MapWindow(QWidget *parent = nullptr);
~MapWindow();
private:
QAction *vehicleAct;
QAction *missionAct;
QAction *backAct;
QMenu *toolMenu;
};
//MapWindow.cpp
MapWindow::MapWindow(QWidget *parent) : QMainWindow(parent), ui(new Ui::MapWindow)
{
ui->setupUi(this);
setWindowState(Qt::WindowMaximized);
vehicleAct = new QAction("Vehicle Selection");
vehicleAct->setShortcut(Qt::CTRL + Qt::Key_V);
missionAct = new QAction("Mission Selection");
missionAct->setShortcut(Qt::CTRL + Qt::Key_M);
backAct = new QAction("Back");
backAct->setShortcut(Qt::CTRL + Qt::Key_B);
toolMenu = menuBar()->addMenu("Tools");
toolMenu->addAction(vehicleAct);
toolMenu->addAction(missionAct);
toolMenu->addAction(backAct);
}
MapWindow::~MapWindow() {
delete ui;
}
When I use the same code in the WelcomeWindow class which is also inherited from QMainWindow it works perfectly. However it doesn't even show a menubar in this second window.
I managed to find the problem. One of my widgets (QScrollArea) was located in the top left corner of the screen which was stopping the whole menubar from displaying for some reason. Moving the QScrollArea down a little bit has solved the problem.
I want to draw a graph on my main form, so I figured I'd use a QLabel and Override that. Like this:
// drawlabel.h
class DrawLabel : public QLabel
{
Q_OBJECT
public:
DrawLabel(QWidget *parent = 0);
private:
void paintEvent(QPaintEvent *);
};
// drawlabel.cpp
DrawLabel::DrawLabel(QWidget *parent)
: QLabel(parent)
{
}
void DrawLabel::paintEvent(QPaintEvent *)
{
qDebug() << "paint event" ;
QPainter painter(this);
painter.setPen(QPen(QBrush(QColor(0,0,0,180)),1,Qt::DashLine));
painter.setBrush(QBrush(QColor(255,255,255,120)));
QRect selectionRect(10, 10, 100, 101);
painter.drawRect(selectionRect);
}
On my main window I droppde a QLabel, sized it to about 500x200 and promoted it to DrawLLabel. When the application is run, a dashed square is drawn on the form.
All good so far.
If I add the line:
this->setText("123456");
into the DrawLabel constructor, or add it into the paintEvent() I don't see the text. I'd also like to be able to have a border around the DrawLabel, but
this->setFrameShape(QFrame::Box);
in the constructor doesn't work either.
What should I be doing to get these to work?
Well, I think you should call paintEvent of base class. Add parameter name e to method:
void DrawLabel::paintEvent(QPaintEvent *e)
And then at end of method add
QLabel::paintEvent (e);
The second option do all painting by yourself directly at paintEvent.
If you want something custom, then implement a custom widget inheriting QWidget. Then you get to draw whatever you want and have whatever members you want.
Your problem is you have overridden the label's paint event, so the code to draw the label text is not executed.
You could call the method from QLabel as Evgeny suggested, but it is better to implement a custom widget instead.
Calling the method from the base class might for example corrupt any previous drawing, unless the method was implemented with calling form derived classes in mind. I don't expect that is the case for stock widgets. I haven't tried doing it with QLabel re-implementations in particular, but I have tried it with other stock widgets and it did not work as expected.
I put a push button into the top-right corner of my main window menu bar:
QPushButton *pb = new QPushButton("Text");
pb->setSizePolicy(QSizePolicy::Preferred, QSizePolicy::Preferred);
QMainWindow *mainWindow;
mainWindow->menuBar()->setCornerWidget(pb, Qt::TopRightCorner);
The initial layout is fine. Sometime later, an asynchronous event changes the QPushButton's text to a longer string, but it gets clipped on the right.
I can see that the QPushButton's size changes when the string is updated. The QPushButton is displayed correctly if the window is resized. The problem appears to be getting the QMenuBar to recognize that the widget's size has changed.
This answer How to auto change QPushButton width and QMenuBar corner widget width when change text of button? suggests resetting the corner widget. I would rather avoid that, because my application's structure makes me jump through several ugly and awkward hoops to reset the corner widget after initializing.
The solution is simple. After updating the text of the button call menuBar()->adjustSize(); I have tested it in Qt5.5 and hope it will work for you.
You can use QWidgetAction as a horizontal menu widget:
class TestMenu : public QWidgetAction
{
public:
TestMenu(QObject *parent) :
QWidgetAction (parent)
{
}
virtual QWidget *createWidget(QWidget *parent)
{
QComboBox *combo = new QComboBox(parent);
combo->setFixedWidth(300);
return combo;
}
virtual void deleteWidget(QWidget *widget)
{
delete widget;
}
};
...
QMenu *menu = new QMenu();
menu->addAction(new TestMenu(this));
menuBar()->setCornerWidget(menu);
I've got a window full of QPushButtons and QLabels and various other fun QWidgets, all layed out dynamically using various QLayout objects... and what I'd like to do is occasionally make some of those widgets become invisible. That is, the invisible widgets would still take up their normal space in the window's layout, but they wouldn't be rendered: instead, the user would just see the window's background color in the widget's rectangle/area.
hide() and/or setVisible(false) won't do the trick because they cause the widget to be removed from the layout entirely, allowing other widgets to expand to take up the "newly available" space; an effect that I want to avoid.
I suppose I could make a subclass of every QWidget type that override paintEvent() (and mousePressEvent() and etc) to be a no-op (when appropriate), but I'd prefer a solution that doesn't require me to create three dozen different QWidget subclasses.
This problem was solved in Qt 5.2. The cute solution is:
QSizePolicy sp_retain = widget->sizePolicy();
sp_retain.setRetainSizeWhenHidden(true);
widget->setSizePolicy(sp_retain);
http://doc.qt.io/qt-5/qsizepolicy.html#setRetainSizeWhenHidden
The only decent way I know of is to attach an event filter to the widget, and filter out repaint events. It will work no matter how complex the widget is - it can have child widgets.
Below is a complete stand-alone example. It comes with some caveats, though, and would need further development to make it complete. Only the paint event is overridden, thus you can still interact with the widget, you just won't see any effects.
Mouse clicks, mouse enter/leave events, focus events, etc. will still get to the widget. If the widget depends on certain things being done upon an a repaint, perhaps due to an update() triggered upon those events, there may be trouble.
At a minimum you'd need a case statement to block more events -- say mouse move and click events. Handling focus is a concern: you'd need to move focus over to the next widget in the chain should the widget be hidden while it's focused, and whenever it'd reacquire focus.
The mouse tracking poses some concerns too, you'd want to pretend that the widget lost mouse tracking if it was tracking before. Properly emulating this would require some research, I don't know off the top of my head what is the exact mouse tracking event protocol that Qt presents to the widgets.
//main.cpp
#include <QEvent>
#include <QPaintEvent>
#include <QWidget>
#include <QLabel>
#include <QPushButton>
#include <QGridLayout>
#include <QDialogButtonBox>
#include <QApplication>
class Hider : public QObject
{
Q_OBJECT
public:
Hider(QObject * parent = 0) : QObject(parent) {}
bool eventFilter(QObject *, QEvent * ev) {
return ev->type() == QEvent::Paint;
}
void hide(QWidget * w) {
w->installEventFilter(this);
w->update();
}
void unhide(QWidget * w) {
w->removeEventFilter(this);
w->update();
}
Q_SLOT void hideWidget()
{
QObject * s = sender();
if (s->isWidgetType()) { hide(qobject_cast<QWidget*>(s)); }
}
};
class Window : public QWidget
{
Q_OBJECT
Hider m_hider;
QDialogButtonBox m_buttons;
QWidget * m_widget;
Q_SLOT void on_hide_clicked() { m_hider.hide(m_widget); }
Q_SLOT void on_show_clicked() { m_hider.unhide(m_widget); }
public:
Window() {
QGridLayout * lt = new QGridLayout(this);
lt->addWidget(new QLabel("label1"), 0, 0);
lt->addWidget(m_widget = new QLabel("hiding label2"), 0, 1);
lt->addWidget(new QLabel("label3"), 0, 2);
lt->addWidget(&m_buttons, 1, 0, 1, 3);
QWidget * b;
b = m_buttons.addButton("&Hide", QDialogButtonBox::ActionRole);
b->setObjectName("hide");
b = m_buttons.addButton("&Show", QDialogButtonBox::ActionRole);
b->setObjectName("show");
b = m_buttons.addButton("Hide &Self", QDialogButtonBox::ActionRole);
connect(b, SIGNAL(clicked()), &m_hider, SLOT(hideWidget()));
QMetaObject::connectSlotsByName(this);
}
};
int main(int argc, char *argv[])
{
QApplication a(argc, argv);
Window w;
w.show();
return a.exec();
}
#include "main.moc"
You can use a QStackedWidget. Put your button on the first page, a blank QWidget on the second, and change the page index to make your button vanish while retaining its original space.
I've 3 solutions in my mind:
1) Subclass your QWidget and use a special/own setVisible() replacement method witch turns on/off the painting of the widget (if the widget should be invisible simply ignore the painting with an overridden paintEvent() method). This is a dirty solution, don't use it if you can do it other ways.
2) Use a QSpacerItem as a placeholder and set it's visibility to the opposite of the QWidget you want to hide but preserve it's position+size in the layout.
3) You can use a special container widget (inherit from QWidget) which gets/synchronizes it's size based on it's child/children widgets' size.
I had a similar problem and I ended up putting a spacer next to my control with a size of 0 in the dimension I cared about and an Expanding sizeType. Then I marked the control itself with an Expanding sizeType and set its stretch to 1. That way, when it's visible it takes priority over the spacer, but when it's invisible the spacer expands to fill the space normally occupied by the control.
May be QWidget::setWindowOpacity(0.0) is what you want? But this method doesn't work everywhere.
One option is to implement a new subclass of QWidgetItem that always returns false for QLayoutItem::isEmpty. I suspect that will work due to Qt's QLayout example subclass documentation:
We ignore QLayoutItem::isEmpty(); this means that the layout will treat hidden widgets as visible.
However, you may find that adding items to your layout is a little annoying that way. In particular, I'm not sure you can easily specify layouts in UI files if you were to do it that way.
Here's a PyQt version of the C++ Hider class from Kuba Ober's answer.
class Hider(QObject):
"""
Hides a widget by blocking its paint event. This is useful if a
widget is in a layout that you do not want to change when the
widget is hidden.
"""
def __init__(self, parent=None):
super(Hider, self).__init__(parent)
def eventFilter(self, obj, ev):
return ev.type() == QEvent.Paint
def hide(self, widget):
widget.installEventFilter(self)
widget.update()
def unhide(self, widget):
widget.removeEventFilter(self)
widget.update()
def hideWidget(self, sender):
if sender.isWidgetType():
self.hide(sender)
I believe you could use a QFrame as a wrapper. Although there might be a better idea.
Try void QWidget::erase (). It works on Qt 3.
I would like to make a QToolButton where the text is the left of its icon. I've tried to find related information, and tried things with:
button->setToolButtonStyle(Qt::ToolButtonTextBesideIcon);
but this sets the text to the right side of the button. I've looked into trying stylesheets, but text-alignment is only for push buttons. Is there any way to do this?
My highest-level goal is to make an interface bar which looks like this:
with a text label and image right beside it. Currently I'm using a toolbar with checkable toolbuttons because of the style (no border unless moused-over, still has the indent with checkable, contains text and an icon...). It's entirely possible that I'm using the wrong type widgets, so if I can't change the layout of this, is there any way to emulate this style?
This is what I currently have:
.
You can use QWidget::setLayoutDirection:
toolbar->setLayoutDirection(Qt::RightToLeft);
Your best bet is probably to create this functionality yourself in a QWidget. It should have a QLabel and a QToolButton (or QPushButton) arranged in a QHBoxLayout. Then you can add this custom widget to the toolbar using QToolBar::addWidget() or QToolBar::insertWidget().
Here's an example of a widget you could use:
#include <QtGui>
class CoolButton : public QWidget
{
public:
CoolButton(QWidget *parent = 0) : QWidget(parent)
{
QLabel *label = new QLabel("Hi!", this);
QToolButton *button = new QToolButton(this);
QHBoxLayout *layout = new QHBoxLayout;
layout->addWidget(label);
layout->addWidget(button);
setLayout(layout);
}
};