There is a "entered" signal for a QTreeView Widget, which I can use to check if my mouse moves over an item.
Is there a way to implement an "left" signal?
Why:
I have a treeView with a lot of items which I also plot via QChart. I want to highlight the plot when someone mouse over the data in the treeview.
I can highlight it via the "entered" signal, but I have no idea how to change it back to the default if the mouse left/mouse is over another item...
entered is a member of QAbstractItemView. You should probably reimplement QAbstractItemView::dragLeaveEvent virtual method.
See this method documentation: http://doc.qt.io/qt-5/qabstractitemview.html#dragLeaveEvent
Related
I have my custom widget inherited from QWidget, and I've connected the widget's menu-calling signal to my slot.
connect(m_ontologyView, SIGNAL(customContextMenuRequested(QPoint)), SLOT(showContextMenuSlot(QPoint)));
Now I want user to be able to change button calling the context menu. Normally it's called with right mouse button, but how do I tell the widget to call the menu with a button of my choice?
I'm on Qt 5.4.0
Instead of using QWidget::customContextMenuRequested, you will need to reimplement the widgets mouse event functions, QWidget::mousePressEvent, QWidget::mouseReleaseEvent and QWidget::mouseMoveEvent. Inside of these events, you can then show you menu using QMenu::popup. (The point can be extracted from the mouse events).
By default QSlider reacts on mouse wheel only when cursor is on it. I want to control slider by mouse wheel not matter where the cursor is (of course only when my application has focus).
What's the best way to achieve that?
I just learned that mouse doesn't generate signals. So looks like I need to override wheelEvent in main window and use raise or lower method in it. But I guess that can cause double increment (or decrement) of slider value when mouse is hovering it.
So once again: What's the best way to achieve what I described?
You can override the wheelEvent() in your MainWindow and redirect it to your slider control, that is indeed one option.
Another option is to install an event filter on the qApp instance. This even filter then can check whether the event type is QEvent::Wheel, and when the receiver is not the slider, then again redirect it to the slider. Should work just as well.
I got a QGraphicsScene that contains QGraphicsItems. On clicking such an item I open a dialog. I now want the item to be displayed in an area of the dialog.
I tried a QGraphicsView (in the dialog) and "pointed" it to the item which works allmost perfectly. The problem is, that it is possible to click the item in the dialog which would open a new dialog.
So my question: is there a easy way to tell QGraphicsView to ignore any input events? If not, is there a easy way to display a QGraphicsItem within a widget?
I am feeling so stupid...
QGraphicsView::setInteractive(false) did the trick.
I am still able to move the icon with the mouse wheel but this can probably be avoided by restricting the scene rect with setSceneRect()
You can install an event filter, on the QGraphicsView, which ignores input events. The Qt documentation states:
In your reimplementation of this function, if you want to filter the event out, i.e. stop it being handled further, return true; otherwise return false.
According to the QGraphicsView docs, dragMode's behavior "only affects mouse clicks that are not handled by any item." It then says "You can define a custom behavior by creating a subclass of QGraphicsView."
In my case I'd like clicks on an item that accepts mouse clicks to call the item's mouse clicks as normal. And I'd like clicks not on those items to start a rubber band drag (also as normal). However, I'd like to be able to ctrl-click the view, and have that start a rubber band drag selection rather than call the item's mouse event methods.
I know how to assess whether or not ctrl is associated with a mouse click event:
if (event->modifiers().testFlag(Qt::ControlModifier))
However, I don't know what to do with this condition, or where exactly to put it. Should I put it in QGraphicsItem, QGraphicsScene, or QGraphicsView? QGraphicsView seems most likely, as the docs somewhat hint.
You need to put the condition to QGraphicsItem like this:
if (event->modifiers().testFlag(Qt::ControlModifier))
{event->setAccepted(false); return;}
Now You can handle the event in Your QGraphicsView.
I've recently been studying Qt, and have the following questions:
What is the difference between QAction and QToolButton?
How do I know when to override QPushButton? For example, should I override in order to be informed when the mouse enters a QPushButton's bounds? I don't need to in order to get the signal click().
Question 1:
QActions are used to define tasks performed by an application in a way which can be understood by a number of different user interface objects. Using an example from the Qt docs for context:
A QAction is defined; it is given an icon image, a text description, a keyboard shortcut and a longer tooltip description, as well as being linked to a user defined function.
newAct = new QAction(QIcon(":/images/new.png"), tr("&New"), this);
newAct->setShortcuts(QKeySequence::New);
newAct->setStatusTip(tr("Create a new file"));
connect(newAct, SIGNAL(triggered()), this, SLOT(newFile()));
Later in the implementation, the QAction is added both to a textual menu bar...
fileMenu->addAction(newAct);
... and an icon-based tool bar:
fileToolBar->addAction(newAct);
The menu bar uses the text description to create an entry in the menu corresponding to the action. Similarly the toolbar uses the icon set on the QAction to create an icon in the toolbar which corresponds to the action. Selecting the menu item, clicking the toolbar icon or pressing the keyboard shortcut will all result in the same effect: that defined by the linking of QAction::triggered() to newFile().
So to directly answer your question: a QAction is an abstract way of defining the various parameters and behaviour of a particular task performed by the application. A QToolbarButton is a UI object (derived from QWidget) created by a QToolbar in response to QToolbar::addAction()
Question 2:
Yes, QPushButton has a clicked() signal inherited from QAbstractButton, but it does indeed lack a way to inform when the mouse has entered its bounds. You have a couple of options in order achieve this, but first you need to first set the mouseTracking property to be enabled. This will allow you to receive mouse move events on the QPushButton even if no mouse buttons are pressed. With that done you need to explore one of the following options:
As you suggest, you could subclass QPushButton and reimplement mousePressEvent in order to respond to the mouse position.
You could install another widget as an eventFilter on the QPushButton, and watch for events of type (QEvent::MouseMove).