First, I draw a lot of QGraphicsItems on the QGraphicsScene. I want to show a thumbnail that can be dragged freely in the bottom right corner of the QGraphicsScene. What classes should I use? How do I use them?
Try to capture Mouse events on QGraphicsItems
Option 1 : using mousemove calculated delta from older position to new and move your graphicsItem Accordingly.
Option 2 : check QgraphicsItem support for drag events or not
Check here Qt: qgraphicsitem drag and drop
Related
I want to allow a user using my application to be able to drag a boundary between two widgets in my window which will resize the two (i.e. you drag it down and the top one will get bigger while the bottom gets smaller, and vice-versa).
Is there anything in Qt designer that will allow a user to resize an element in the window, within certain constraints?
Thank you
What you're describing is called a QSplitter widget. In Qt Designer, you can create one by selecting 2 or more widgets, and then clicking the splitter button on the toolbar at the top. It's in the same location as the layout buttons. It will place those widgets inside a QSplitter. You still need to place the splitter widget inside another layout. It will create a handle between them to let you resize the portion that each widget gets.
You're looking for the QDockWidget. It can do all that you described above and more. The user can dock the widget to different sides of the window, changing which widget is on the top or bottom. You can customize the minimum and maximum sizes, as well as default sizes.
I have a QGraphicsView on which there is a QGraphicsScene on which there are QGraphicsRectItem.
For each of these 3 classes, I've implemented mousePressEvent().
Now, I would want to know what happens when we click. Does the event first go to view, then to scene, then to item?
Can you please explain in detail about how mouse clicks are handled for each of these 3 classes?
I have already implemented eventFilter for QGraphicsView to support zoom and pan functionalities.
Example:
In the image below, I would want to get the innermost green rectangle (with text 230, 30) when I click on it...
I have a QGraphicsScene. I have a video running on the scene. On top of video I add a zooming window which is a QGraphicsItem. I drag and drop this window using drag events of QGraphicsScene. This works fine.
I have to show the scene co ordinates everytime the mouse moves. For this I use a QGraphicsTextItem in MouseMoveEvent of graphics scene. The problem is when I write the MouseMoveEvent the drag and drop events stop responding.
Why does this happen?
Thank You
You likely forgot to call the base class's method:
void MyScene::mouseMoveEvent(QGraphicsSceneMouseEvent * ev) {
QGraphicsScene::mouseMoveEvent(ev);
// do your own processing
}
Another possible factor is your coordinate item being in the way of the drop - you could simply move it down a pixel or two so that it's below the mouse pointer's hot spot.
I'm stuck on how to approach this. I have a QGraphicsItem within a scene, and I'm passing a hover event from the scene to this child. While the move event occurs (I'm just using mouseMoveEvent with mouse tracking on), I want another QGraphicsItem to follow the cursor.
I don't need any collision detection, drag and drop, etc. Just an item that follows the cursor. The only two ways I can think of are...
While the mouse moves, draw a new QGraphicsItem at the mouse position. I would need to clear the scene, redraw everything, and draw the new position on top.
Somehow use the animation framework and whenever the mouse moves, animate the QGraphicsItem to move to the new mouse position in 1 millisecond.
I'm probably either overthinking this or unaware of another way to do this... any suggestions?
I did it like this
Create the GraphicsItem cursor which will be moved with mouse-cursor, and store its pointer somewhere (in scene subclass for instance. I have a toolset, so for me it's in one of these tools)
Set its Z-Value (QGraphicsItem::setZValue) so that the cursor will be painted above all other items in your scene
Track QGraphicsScene::mouseMoveEvent events, forward these events down to the cursor pointer, and update item's position
that's it.
I guess it corresponds to your solution 1, except you don't have to clear the scene thanks to z-value feature.
I am having QListWidget, i want to have a Transparent Scrollbar with Image.
Initially that scrollbar should be hidden on scroll only it should show.
How i Can achieve this in Qt ?
Any examples or ideas are welcomed.
How i can apply image to Listview Scrollbar.
Here are the three things you can look at to be able to control the scroll bar for most kinds of widgets in Qt:
VerticalScrollBarPolicy
HorizontalScrollBarPolicy
enum Qt::ScrollBarPolicy.
To be able to track how the user interacts with your QListWidget or any Widget for that matter you need to subclass it and implement the virtual methods from the QWheelEvent and possibly the QKeyEvent.
Scrolling is typically done with the mouse wheel and with the keyboard arrow keys and sometimes page-up and page-down and spacebar. I haven't done a lot with QListWidget, but you should double check which keyboard events/mouse events trigger scrolling.
These events will cause scrolling event even after you set either or both of the ScrollBarPolicies for the widget to be Qt::ScrollBarAlwaysOff.
First you should put in the constructor of your widget
this->setVerticalScrollBar(Qt::ScrollBarAlwaysOff);
this->setHorizontalScrollBar(Qt::ScrollBarAlwaysOff);
So you just need to setMouseTracking(true) for the widget (so that it tracks more than just the clicks) and reimplement at the very least wheelEvent(), and when a wheel event occurs, set the vertical/horizontal scroll bar policies to true and call update on your widget.
If you want to turn the scrollbars back off after a few milliseconds after they have started scrolling, you will need to create a QTimer in your constructor for your subclassed widget and connect it to a slot that sets the scroll bar polices on the timeout. Then you start/restart that timer every time the user does a wheelEvent().
As far as applying an image to the ListView Scrollbar, you should look into subclassing QAbstractScrollBar, if you want to actually put an image on it or change the way it looks. Setting up some tool buttons may also be the way to go if you are trying to put buttons with different icons in place of the scrollbar.