Question/Issue
I tried reimplementing the event method in a custom delegate to handle clicks. The delegate is used to render table cells in a table view. However, I do not get any events for the delegate (the method is never called according to the debuger). Is there anything special I need to do so my delegate can track events (in particular mouse entering/exiting, clicks)?
Context
I would like to create my own data representation for table cells. The functionality should be close to a button, but slightly different. I read that the two options for implementing buttons in table are either setting a cell widget which supposedly has a high performance cost (I did not quite understand why) or using a delegate.
Since I want different behaviour than that of a button, and for the speed myth I decided to go with a delegate.
Mouse events are send to the QAbstractItemDelegate::editorEvent() method, even if they don't start editing of the item.
See: http://doc.qt.io/qt-5/qabstractitemdelegate.html#editorEvent
Related
I'm trying to understand sequencing of property changes and mouse events inside ListView.
To detect a change is there a difference between observing selectedIndex vs selectedItem?
To drag and drop ListView items is there any difference between registering onDrag.. events against ListView vs each ListCell?
Is there any scenario where a "onDragDetected" event would be received before the selection model (which I'm observing) is updated?
Thanks
To detect a change is there a difference between observing
selectedIndex vs selectedItem?
Not really; I think this is just a matter of whichever is the most convenient for you to use.
To drag and drop ListView items is there any difference between
registering onDrag.. events against ListView vs each ListCell?
I would advocate for registering with the ListCell. There's no direct way to check a mouse event on the ListView and then determine which cell the mouse event occurred on. You would have to fall back on the selected item, and that's not really semantically the same thing. (For example, how would you handle drag on empty cells, which wouldn't change the selection...?)
Is there any scenario where a "onDragDetected" event would be received
before the selection model (which I'm observing) is updated?
That's implementation dependent. I think the current implementation uses a mousePressed event to handle selection (though I'm not certain), so it should trigger before the drag is detected, but do you really want to rely on that implementation not changing in a future release?
IMHO, relying on the selected item just feels wrong here. It's semantically different to what you want: you actually want to know "which item the user clicked on", not "which item is selected". Sure, the two are related, but they're not the same thing, so in a way you'd be introducing a dependency on the selection API that should be independent of the thing you're trying to achieve. That is most definitely an opinion, though. Your mileage may vary...
I need to be able to trigger an event on change, but only when user focus out of the input text.
Is there any one event I can use?
I guess I can use a combination of both, by finding out which of them triggers last, and only use that, if the other has been called, but that introduces some complexity and clutters the code.
There's no single event that combines both of these concepts. You'll need to write some custom logic to do what you're describing.
Using the mx.managers.FocusManager getFocus() method you can find the component that currently has focus. In the change handler on the TextInput you can check if this TextInput currently is the component with focus. If not, you can go about your business.
My custom QListView has delegates to paint the items. I'd like to add a live control to some of the row items (like a QLineEdit), that'll always be present in the row and will automatically scroll correctly with the list.
Since items are not widgets, I cannot assign a control to be a child of an "item", thus scrolling will leave the control in its fixed spot within the QListView widget.
Is there another way?
Is that even possible?
Normally the edit widget is created (and positioned) by the delegate when an QEvent::EnterEditFocus event occurs then destroyed when a subsequent QEvent::LeaveEditFocus occurs and the data is sent back to the model. The delegate should then repaint with the new model data.
Could you expand on what you mean by a "live" control?
Why would you want to have an edit widget constantly open? I think a better way to do this would be to create a delegate which paints the normal view (i.e. for Qt::DisplayRole) in a way which you want. Assuming you create your subclass view correctly, the delegate should still update when the model changes.
If you really want to do what you're asking though, I suspect you might be able to by:
creating your own item delegate (subclassing QAbstractItemDelegate)
reimplement createEditor() to use a QLineEdit
then use the delegate's updateEditorGeometry()
Have a read of the Delegate Classes section of the Introduction to Model/View Programming though first. The Spin Box Delegate Example and Pixelator Example are worth studying too if you haven't already.
Environment: Flex/As3/Cairgorm/composite component.
I have two comboboxes and two datagrids such that the selection of combobox 1, inserts data into combobox two and the fist datagrid. The selection of combobox 2 inserts data into datagrid 2.
I have setup the change event so that the user selection on each of the combo boxes do the right thing. The problem is that on the initial load of the comboboxes, the change event does not fire and subsequent synchronization data loading does not happen.
Is there an event for getting the itemselected (1st item) after the combobox is initialized?
I found my own answer. Using the updateComplete event on each of the comboboxes did the trick.
[EDIT]
It turns out that updateComplete did not work as expected. What I really needed is the dataChange event. However, it appears that this event does not fire for comboboxes even though it is listed as a valid FlexEvent for this component.
I tried a number of other events (valueCommit, creationComplete, initialize) but all of these fire multiple times, overlap with change, and are not useful for this usecase.
In the end, I created a gludge of a chain of calls for the initialize path and change path.
If anyone else has a better way, I'd be very interested.
I would like to display editors for all cells in a row when a user begins editing any cell in a QTableView. I have made several attempts but I cannot obtain the correct behaviour.
The only way to open multiple editors is by QAbstractItemView::openPersistentEditor() - attempts to successively call QAbstractItemView::edit() results in only one editor.
I cannot use signals such as clicked() and doubleClicked() from QAbstractItemView to invoke editing, because then it would not respect the edit triggers of the view.
There appears to be no "editing complete" signal. I would like to connect this signal to a slot that calls closePersistentEditor() for cells in the editing row.
Any suggestions would be appreciated.
Thanks!
I hate to be the bearer of bad news, but I can't think of any easy way to do what you want. I can think of a couple of options, each more painful than the last:
You could create a delegate that always shows the editors, and when the user changes the selected row, set that delegate for the newly selected row, and the original delegate for the deselected row.
You could try inheriting from the table view, and overriding the behavior for drawing the appropriate items for everything in the given row. I have no idea how hard this would be, but I doubt it would be trivial.
You could create your own view to display the model. I've never done this, and I'd hate to think about all that would be required to "complete" support the models. However, to match with one specific model, you might be able to get away with it.