we're working on a Qt C++ Widget project and recently ve'we run into trouble. We're Qt rookies.
On our widget there are two QGraphicsView which need to resize automatically when the window is resized (we've done that) and keep the content inside them resized/fit/scaled accordingly to...
So we've figured we need to somehow hook to onResizeEvent or find which slot does it. But we're somehow lost as to how to do it.
P.S.: Please excuse my english.
If you have a QWidget you only need to reimplement the resizeEvent function.
void QWidget::resizeEvent ( QResizeEvent * event ) [virtual protected]
In the Qt documentation you can find the scribble example for a full code example: http://doc.qt.io/qt-5/qtwidgets-widgets-scribble-example.html
Alternatively you can install an event handler and grab the QEvent::Resize.
How to install event filters is described here: http://qt-project.org/doc/qt-4.8/eventsandfilters.html
You can make your custom class which inherits from QGraphicsView. You should reimplement resizeEvent( QResizeEvent *event ) in your custom QGraphicsView like:
void MyView::resizeEvent(QResizeEvent *event)
{
fitInView(0, 0, 500, 500,Qt::KeepAspectRatio);
QGraphicsView::resizeEvent(event);
}
This way the view will always display the whole scene. I.e. if the window size is changed and the graphicsView is resized, The scene gets scaled and you can see everything appropriately.
If you are resizing in some slot then you can use sender().
Btw you can always use debugger or logs/backtraces to get such information.
Related
To explain the situation, I have a QMainWindow with plenty of stuff inside.
My goal is to make some kind of a notification that appears at the bottom right corner of this window.
The notification widget must be over every other widgets.
So far I've created that Notification widget that inherits from QWidget.
By setting the QMainWindow as its parent I've got it 'floating' on top of every other widgets. It doesn't belong to any layout.
Now the big issue is to make it stick to the bottom right corner. I managed to place it manually but what I want now is to move it upon a resize event.
Unfortunately since it doesn't belong to any layout it doesn't receive any resizeEvent, so I can't overload the resizeEvent() function.
An attempt was to make the QMainWindow emit a signal in its resizeEvent method but I am not really happy with this method. Especially because in the Notification widget constructor I have this connect(static_cast<MainWindow*>(parent), &MainWindow::resized, this, &Notification::update_position);, and it kind of breaks the genericity of the widget since its parent must be a MainWindow widget.
So the question is how can one widget react to another widget event ?
In my case here how can the notification widget be notified when its parent is getting resized ?
And I forgot to mention that I don't want the MainWindow widget to know anything about this notification widget. The notification widget can be managed on its own. You just call something like new Notification(parent) and it will do its stuff on its own
Any ideas are welcome,
Thanks in advance :)
You can install the notification widget as an event filter for its parent, e.g.:
NotificationWidget::NotificationWidget(QWidget *parent) : QWidget(parent) {
parent->installEventFilter(this);
}
bool NotificationWidget::eventFilter(QObject *obj, QEvent *event) {
// normal event handling
bool ret = QObject::eventFilter(obj, event);
if (event->type() == QEvent::Resize) {
// Parent resized, adjust position
}
return ret;
}
I'm trying to write a circuit designer software in QT on Linux. I'm using KDE 5 Plasma desktop and QTCreator as an IDE.
I tried to use QFrame paintEvent to paint on it, and it worked, but when im grabbed the window inside QFrame it moved.
I know about QGraphicsView, but i cant make a custom class and promote it based on that(it's not listed).
How can i create a custom class from a container(QFrame, QGraphicsView or anything) where i can override paint event and also it doesn't move window if i grab it?
Sorry for my poor english.
QGraphicsView inherits from QAbstractScrollArea which inherits from QFrame itself.
So you can keep the QFrame in the form, and keep it promoted to your canvas class, but simply make you canvas class inherit QGraphicsView instead.
Although, my Qt has two differences in behavior from the OP (but I don't use KDE):
Clicking on a QFrame and moving the mouse doesn't move the whole window for me. I guess this behavior for the OP could be changed by reimplementing void mousePressEvent ( QMouseEvent * event ) in the canvas class and giving it an empty code instead. (doc)
I can put QGraphicsView in my ui files, and I can right click on them to promote them to another custom-defined class.
Edit: Found the reason why the window moves on KDE!
I have a QPushButton that I am styling with a border-image through a stylesheet. However, the image quality is poor because the image isn't being drawn using antialiasing.
Is there any way to enable antialiasing simply without subclassing QPushButton and giving it a new painter? I don't really want to do that because I'm using the style sheet extensively and would have to create a bunch of QProperties to emulate the existing pseudo-state functionality.
You can normally set the Anti-aliasing flag, on a QPainter object using the setRenderHints method. This is normally done by Subclassing the widget and overriding the paintEvent.
According to the Qt Docs for QPainter:
... When the paintdevice is a widget, QPainter can only be used inside a paintEvent() function or in a function called by paintEvent() ...
Without subclassing, you will be limited to intercepting the paintEvent using an Event Filter and setting the flag yourself.
You will need to create a class that overrides the event handler for your object. This class will be installed using QObject::installEventFilter. This class will need to filter the events to handle the specific ones that you care about (QPaintEvent). Then it will need to create a QPainter object that takes in the originating object(using the second constructor) as its device as shown in this qtforum post. This works because QWidget inherits from QPaintDevice.
...
myView::handlePaintEvent(QObject *obj, QEvent *eve)
{
QPainter painter(static_cast<QWidget *>(obj));
}
...
From here you should be able to set the proper Render Hints to what you need them to be.
This same event filter class can be installed on numerous objects so the same functionality can be added very quickly and without subclassing any other widget.
I want to render the video from my webcam into QWidget. I've set QWidget, as a parent to IVideoWindow. Here is the code:
m_iVideoWindow->put_Owner((OAHWND)widget_->winId());
m_iVideoWindow->put_WindowStyle(WS_CHILD | WS_CLIPCHILDREN);
m_iVideoWindow->put_Left(0);
m_iVideoWindow->put_Top(0);
widget_->setChild(m_iVideoWindow);
Also i've reimplemented QWidget's resize event, and so when it's resizing it also resizes the IVideoWindow. Everything works good, when the widget is not set to the QLayout. When is - it becomes blank. That is the problem.
I think when Qt draws its widgets, it doesn't redraw them unless it knows they need to be updated. I'm also unsure as to whether it passes on whatever redraw stuff windows requires, to the window you've assigned as a child of the widget.
When I embed my own windows in a Qt widget, I use http://qt.nokia.com/products/appdev/add-on-products/catalog/4/Windows/qtwinmigrate/, but that may not solve your problem, as I still have to use a QTimer to force an update of my window.
I am trying to create an app in Qt/C++ with Qt4.5 and want the any active windows to change opacity on a mouseover event...
As i understand it, there is no explicit mouseover event in Qt.
However, I got rudimentary functioning by reimplementing QWidget's mousemoveevent() in the class that declares my mainwindow. But the mainwindow's mousemoveevent is not called whenever the mouse travels over any of the group boxes i have created in there (understandbly since QGroupbox has its own reimplementation of mousemoveevent).
So as a cheap work around, I am still using the mousemoveevent of my mainwindow but a query the global mouse position and based on the (x,y) position of the mainwindow (obtained through ->pos()) and the window size (-> size -> rHeight and rWidth), I check if the mouse is within the bounds of the area of the mainwindow and change the opacity thus.
This has had very limited success. The right border works fine, the the left changes opacity 4 pixels early. The top does not work (presumably because the mouse goes through the menubar and title bar) and the bottom changes way too early.
I thought of creating an empty container QWidget class and then place all the rest in there, but i felt that it would still not solve the big issue of the base widget not receiving the mousemoveevent if it has already been implemented in a child widget.
Please suggest any corrections/errors I have made in my method or any alternate methods to achieve this.
p.s. I doubt this matters, but I am working Qt Creator IDE, not Qt integration into VS2008 (it's the same classes anyways - different compiler though, mingw)
Installing event filters for each of your child widgets might do the trick. This will allow your main window to receive child events such as the ones from you group boxes. You can find example code here.
You may be interested in Event filters. QObject proves a way to intercept all events zipping around your application.
http://doc.trolltech.com/4.5/eventsandfilters.html#event-filters
If I understand what you are attempting to do, I would reimplement the widget's enterEvent() and leaveEvent(). The mouse enter event would trigger the fade-in and the leaveEvent would trigger the fade-out.
EDIT: After re-reading several times, I'm still not sure what you are trying to accomplish. Sorry if my suggestion doesn't help. :-)