I've made a widget derived from QTableWidget and I would like to execute a slot each time the a column or a line is resize, and each time the widget is resized. How to do that as there is no signal for that ?
Thank you very much.
For resizing of the widget itself: Inherit from QTableView, add a signal reimplement resizeEvent. In your resizeEvent emmit your new signal and call the base implementation of resizeEvent to actually do the resizing.
For resizing of columns: Use the signals from the associated QHeaderView which you can obtain with horizontalHeader
Related
I'm new to Qt programming and I am developing a drawing application. I have a class MyWidget which has a member QGraphicsView. MyWidget is a member of another class MainWidget (which has other widgets as well and all of them are in a layout).MainWidget is the central widget of my subclass of QMainWindow.
I have created functions to scale the view with the mouse wheel event and a function to drag the scene around.
The problem is - I want to set the Scene's size to be fixed, and to be 3 times the size of the view, but since the view is managed by a layout in order to take as much space as possible I can't get the view's size?
Any help appreciated.
the size property will give you the current size of your widget:
http://qt-project.org/doc/qt-4.8/qwidget.html#size-prop
Alternatively, you could subclass QGraphicsView and re-implement the resizeEvent:
http://qt-project.org/doc/qt-4.8/qwidget.html#resizeEvent
For a full example, have a look into:
http://qt-project.org/doc/qt-4.8/widgets-scribble.html
You can definitely get the view's size. There are two ways to go about it:
Attach an event filter object to your view: myView->installEventFilter(filterObject). The filterObject's eventFilter method will be invoked for all events reaching your view, including resize events.
Use a custom view class and reimplement resizeEvent. This method gets called each time the widget is resized. Do note that designer allows you to add custom classes without having to write plugins.
I have a QListWidget and I have set it to accept drops, the mode to be DragDrop etc and I can move QListWidgetItems all around the place (inside the QListWidget of course).
I like this behavior and I want it to let it as is, but I also want my QListWidget to accept drops from a QTreeWidget as well. If I attempt to reimplement the dropEvent() of my QListWidget then I lose the default behavior.
Is there any way to just extend the current behavior so as to have both drag-drop between listwidget items and drag-drop from the treewidget to the listwidget or I have to completely re-write both behaviors in my dropEvent() reimplementation?
Thanks a lot for any answers :)
Two ways:
implement a standalone event filter and make it act upon QEvent::Drop. Install it on your original QListWidget. Return false so that the original dropEvent() handler is called afterwards.
inherit from QListWidget, reimplement dropEvent(evt) and as a last statement, call QListWidget::dropEvent(evt);. Your original behavior will be retained.
No.
Subclass QListWidget, reimplement
virtual void QListWidget::dropEvent ( QDropEvent * event )
and explicitly call
QListWidget::dropEvent(event);
whenever you need the default behavior.
How to call a parent class function from derived class function?
I have a widget container I wish to manually paint.
However, it is located within my GUI's MainWindow class.
Is there any way I can register on the paint event for a specific QWidget, so my own function will be called ?
Look for eventFilter. It will help you
The most straightforward way would be to override the paintEvent on the widget
you would like to draw in a custom subclass, and then use that class in your GUI.
I'm developing a custom widget with QGraphicsScene/View and I have no prior experience with it.
The custom widget is an image viewer that needs to track mouse movement and send signal(s) to it's parent dialog / window. The signal(s) will be the position of the pixel under the mouse cursor and it's color (in RGB). A status bar will use that information.
I use a QGraphicsPixmapItem to display the image I load from a file in the scene.
Thanks.
First of all you have to implement the mouseMoveEvent in your custom item. In this function you can easily get the mouse position calling the pos function. You can get the rgb value if you transform the item's pixmap into image and call the pixel function. You should consider storing the QImage as member variable in order to avoid multiple transformations. Finally you have to emit a custom signal. Sample code follows:
void MyPixmapItem::mouseMoveEvent(QGraphicsSceneMouseEvent * event)
{
QPointF mousePosition = event->pos();
QRgb rgbValue = pixmap().toImage().pixel(mousePosition.x(), mousePostion.y());
emit currentPositionRgbChanged(mousePosition, rgbValue);
}
Notice that QGraphicsItems do not inherit from QObject so by default signals/slots are not supported. You should inherit from QObject as well. This is what QGraphicsObject does. Last but not least I would advise you to enable mouse tracking on your QGraphicsView
I found the mouseMoveEvent approach to not work at all, at least not with Qt5.5. However, enabling hover events with setAcceptHoverEvents(true) on the item and reimplementing hoverMoveEvent(QGraphicsSceneHoverEvent * event) worked like a charm.
The Qt docs on mouseMoveEvent() provide the clue:
"If you do receive this event, you can be certain that this item also received a mouse press event"
http://doc.qt.io/qt-5.5/qgraphicsitem.html#mouseMoveEvent
I am somewhat new to qt and working on an already written code.
I am trying to do something whenever a specific widget in my Qsplitter is collapsed.
for this I need a signal from qsplitter or qsplitterhandle.
A QSplitter will emit the signal splitterMoved(int pos, int index) when it is resized. You should be able to identify the splitter you are interested in with index and then look at the value of pos to determine if it is collapsed.