I'm looking for some ways to implement a simple custom tooltip for QGraphicsItem.
I know that I can use setToolTip to set text for tooltip. Now what I want is to change the text dynamically when the mouse hovers at different parts of a QGraphicsItem object.
What I'm thinking to do is when I get an event QEvent::ToolTip, I change the tooltip text in that event handler. However, I cannot find an event function that recieve QEvent::ToolTip for QGraphicsItem.
Or is there some ways to handle an event that mouse hovers for 2 seconds.
How can I make it?
You could implement the hoverMoveEvent in your derived QGraphicsItem class, and set the tooltip based on the position within the graphics item
void MyItem::hoverMoveEvent(QGraphicsSceneHoverEvent* event)
{
QPointF p = event->pos();
// use p.x() and p.y() to set the tooltip accrdingly, for example:
if (p.y() < height()/2)
setTooltip("Upper Half");
else
setTooltip("Bottom Half");
}
Notice that you have to enable hover events for your item.
Related
I am trying to implement in my program, that if the mouse hovers over my QChartView widget, that I get back the coordinates of the cursor.
I already tried, by installing an event filter on the widget
ui->chartView->setMouseTracking(true);
ui->chartView->installEventFilter(this);
and then writing the method for a mouse event
void MainWindow::mouseMoveEvent(QMouseEvent* event) {
qDebug() << event->pos();
}
but, i only get output when I click on the Mainwindow and hold the mousebutton which I clicked. When I click on the widget chartView I dont get any output.
I need to get output, when the mouse is hovering over the chartview
You don't need an event filter. You need to reimplement the methods QWidget::enterEvent() and QWidget::leaveEvent().
enterEvent() is called when the mouse enters the widget and leaveEvent() when it leaves it again.
The situation is:
In side a QGraphicsView, I used its doubleClickEvent function to create a QGraphicsItem.
I rewrite the QGraphicsItem's mousePressEvent function to simply print a qDebug information.
However, what I found is that: even if I just double click to create that QGraphicsItem, the newly created QGraphicsItem's mousePressEvent is also called.
How would this happen? What can I do to prevent this?
A QGraphicsView is a widget, so it has a doubleClickEvent. In contrast, a QGraphicsItem is not a widget, but has a mousePressEvent.
When you override events, if you don't want them to be propagated to other objects, you need to accept the event to tell the system that you've handled it.
void MyGraphicsView::mouseDoubleClickEvent(QMouseEvent * event)
{
// Create a graphics item..
...
event->accept(); // tell the system that the event has been handled
}
Without accepting the event, the double click is passed on to the QGraphicsScene and then QGraphicsItem.
If you want to be able to double-click to create an item when clicking on an empty area of a scene, but have an item react if you double-click on an item, you can override the scene's mouseDoubleClickEvent instead of the view and check if there's an item at the cursor position before deciding upon whether or not to create an item, or pass the event on.
void QGraphicsScene::mouseDoubleClickEvent( QGraphicsSceneMouseEvent * mouseEvent )
{
if(items(mouseEvent->scenePos()).isEmpty()) // if no items are at this position
{
// create new graphics item
...
mouseEvent->accept(); // don't propagate the event
}
// no items, so allow the event to propagate by doing nothing
}
I would like to be able to move a QSlider with arrows of the keyboard at any time.
I want to be able to click anywhere on the QWindow and keep QSlider activated to move the cursor with the arrows.
My problem is that move the cursor with arrows is only allowed if we click on the QSlider before.
I hope my question is clear enough.
Does anyone know how to move the QSlider with arrows of the keyboard without clicking on the QSlider before please?
There are two approaches:
In Qt terms, you'd like to give slider the focus. Widgets have the setFocus method, so you need to call slider->setFocus(Qt::OtherFocusReason).
Since you want the slider to get focus whenever the underlying window has focus, you need to put the setFocus call in your implementation of focusInEvent for the parent widget.
You can forward the key events from the underlying widget to the slider. In the parent widget, reimplement keyPressEvent and keyReleaseEvent. When the desired keys are detected, forward them to the slider:
// same for keyReleaseEvent!
void MyWindow::keyPressEvent(QKeyEvent * ev) {
if (ev->key() == Qt::Key_Up || ev->key() == Qt::Key_Down) {
slider->event(ev);
}
}
I have a QPushButton with an image that has two areas that I want to handle differently when clicked. Due to the positioning on the image, I cannot really use separate buttons for the two images.
What I'd like to do is, in the slot where I am handling the click, have it check the coordinates of the click to determine which area was clicked.
Is there a way to access this?
This is what first comes to mind. It should work, although there may be a simpler way:
Create your own class that derives from QPushButton.
Override the necessary mouse events (mousePressEvent and mouseReleaseEvent) and, before calling the base class implementation, set a property in your object using setProperty with the position of the mouse click. (The position is available from the event parameter.)
In the slot handling the event, use sender() to get the button, and read the property using property().
If you don't need to treat your object as the base class (QPushButton*) you could just create a new signal that includes the mouse event and attach that to your slot. Then you wouldn't need the property at all.
You can get the current mouse position using QCursor::pos() which returns the position of the cursor (hot spot) in global screen coordinates.
Now screen coordinates are not easy to use, and probably not what you want. Luckily there is a way to transform screen coordinates to coordinates relative to a widget.
QPoint _Position = _Button->mapFromGlobal(QCursor::pos());
This should tell you where on the button the mouse was when the user clicked. And you can take it from there.
Building on #Liz's simple mechanism, here's what I did; this is in a slot method that is called on pressed() but generalizes to other situations. Note that using pushButton->geometry() gives you coordinates that are already in global space so you don't need to mapFromGlobal.
void MainWindow::handlePlanButtonPress()
{
int clickX = QCursor::pos().x();
int middle = m_buttonPlan->geometry().center().x();
if ( clickX < middle ) {
// left half of button was pressed
m_buttonPlan->setStyleSheet(sStyleLargeBlueLeft);
} else {
// right half of button was pressed
m_buttonPlan->setStyleSheet(sStyleLargeBlueRight);
}
}
Greetings all,
As seen in the picture
I have an extended QWidget object (which draws the cell images and some countour data) inside a QScrollBar.
User can zoom in/out the Image (QWidget size is changed according to the zoomed size of the QImage ) using mouse wheel.
I process the events (mouseMoveEvent(),wheelEvent()..etc) by implementing the listener methods in QWidget.
My problem is ,I can only perform zooming (and other events) when the mouse pointer is over the QWidget.
If the mouse point is over the QScrollBar (the gray area in the image) ,those events are consumed by the QScroolBar.
Any tips,
[Edit] Sorry I was refering to QScrollArea , not QScrollBar.
thanks,
umanga
I'm uncertain if you want the scroll wheel to only ever be used for zooming the image or if you want the scroll wheel to control zooming when the image is smaller than the scroll area viewport and then use the scroll wheel to do scrolling when the image is larger than the scroll area viewport. In either case, you should be able to customize how the wheel is handled with the following:
Since I've not actually tried this one, I'm not sure if it will work. The hope is that if you install an event filter and set ignore on the event, the event will still be propagated back to your image widget. This will allow you to leave your current mouse handling in the image widget intact.
bool YourImageWidget::eventFilter(QObject *obj, QEvent *event)
{
if((obj == scrollAreaPointer) && (event->type() == QEvent::Wheel))
{
if(!scrollAreaShouldHandleWheel)
{
event->ignore();
}
}
return false; // always pass the event back to the scroll area
}
The scrollAreaShouldHandleWheel flag is a boolean you would set from your image widget based on whether or not you want the scroll area to handle the wheel events.
Somewhere in your code you would install your image widget as an event filter for the scrollarea.
scrollArea->installEventFilter(imageWidget);
If this doesn't work, you can always use this filter to make sure your widget gets the event and handle it directly and then return true so that the scroll area won't be able to receive the event.
I recommend you use QGraphicsScene and QGraphicsView. The graphics framework already provides a lot of useful features (including viewport transformation). And the QGraphicsView is a scroll area.
have you done grabMouse() for Qwidget i.e for the one which you display image?