In a designer-based QT GUI application I'm using a QTreeView to show a tree of elements that is provided by an instance of QStandardItemModel.
The tree-view is multi-column and all elements in the first column are checkable. The screenshot shows an example of how this currently looks like:
Now let's say I'd like the user to be able to select different names for "point". The idea is to have a QComboBox right next to each of the checkboxes. And as alternatives to "point" he may chose from a set of strings, e.g. "point", "pt" and "coord2D". Later on I'd like all selections for all duplicates of "point" to be synchronized but let's start simple...
I'm not too familiar with the idea but to me it looks like the way to go is to create an ItemDelegate for the view as described in the QT Documentation or in this topic (both links refer to QTableWidgets instead of QTreeViews).
So what I did as a first step is I took the example delegate ComboBoxDelegate from the stack overflow question mentioned above and called it from within my application using this code also taken from a related question:
QStandardItemModel* model = new QStandardItemModel(20,2);
ui.tvStructures->setModel(model);
ui.tvStructures->setItemDelegate(new ComboBoxDelegate());
for (int row = 0 ; row < 20; ++row)
{
for (int col = 0; col < 2; ++col)
{
QModelIndex index = model->index(row, col, QModelIndex());
model->setData(index, QVariant((row+1) * (col+1)));
}
}
Note that I placed this code inside the constructor of the parent QDialog where the control element is located. What I ended up is a 2-column table as expected but without any combo boxes. In fact when debugging the code I observe that the constructor of the delegate is called (during the new operation) but none of createEditor, setEditorData, setModelData or updateEditorGeometry every get called. I thought this may be due to the fact that some connection magic is overwriting triggers required to do the drawing but even if I remove all code that refers to the tvStructures QTreeView apart from what I have posted I still can't see any combo boxes.
What's missing?
Note that I'm using the somewhat outdated QT 4.7.1
Looks like you're missing a parent for new QComboBoxDelegate. You can use the QDialog you mentioned as parent.
Also: follow this lengthy example to make sure you're not missing anything else.
Related
I'm looking for a way to detect whether a Qt widget's ToolTip is visible at the moment when a particular key combination is pressed. If it is, I want to copy the ToolTip's text to the clipboard.
Specifically, I have a QListView containing abbreviated strings, which is set up (via the Qt::ToolTipRole of the associated model) to show the full string of the appropriate list item when the mouse is hovered over it. The behaviour I'm looking for is that if the user presses CTRL-C (as detected by a QShortcut) while the tooltip is visible, then the tooltip text is copied to the clipboard.
My original idea was to use the children() method of the QListView widget to see if there was a tooltip preset among them:
// Inisde the slot connected to QShortcut::activated...
auto children = _ui -> myListView -> children();
QString selectionText;
for (const auto & child : children)
{
if (qobject_cast<QToolTip *>(child))
{
selectionText = qobject_cast<QToolTip *>(child) -> text();
break;
}
}
...but this failed because it turns out that QToolTip does not inherit from QObject.
I've also thought of screening for QEvent::QToolTip events in the ListView's main event handler, and while I could probably get this to work it seems excessively low-level; I'd need to use screen co-ordinates to determine which item in the list was being hovered over and look for the widget's timeout to check that the tooltip hadn't disappeared again by the time that the QShortcut was fired. I'd be disappointed if there weren't a simpler way.
Is there an obvious way forward that I've failed to see?
There are probably several possible solutions, but I am afraid none of them is simple. What I would do is to use the implementation detail that the tooltip actual widget is called QTipLabel. See https://code.woboq.org/qt5/qtbase/src/widgets/kernel/qtooltip.cpp.html#QTipLabel and it inherits from QLabel so you can easily get the text from it.
I am afraid the following solution is just a savage hack. I have not tested it, but it should work.
I would override the data model for your view, specifically override method data() which would call the data() method of the original model class but cache the last value which was returned when this method is called with role == Qt::ToolTipRole.
Then you need to catch the shortcut you are interested in. After it is caught, you get all qApp->topLevelWidgets() https://doc.qt.io/qt-5/qapplication.html#topLevelWidgets` and go through them and check if any of them has class name equal to QTipLabel (use QMetaObject::className()) and is visible, i.e. isVisible() == true.
If you get this visible QTipLabel widget (you hold it via QWidget*), qobject_cast it to QLabel* (you cannot cast it to QTipLabel beause you do not have access to the definition of QTipLabel class because it is in private Qt source file) and get the text with QLabel::text(). If the text is the same as the text which you stored in step 1, then yes, this is the text you are looking for and you can copy it to clipboard or do whatever yo want with it.
Nasty, isn't it? But it is the simplest what I can think of.
PS: I believe that step 1 can be implemented also by catching QEvent::QToolTip for your view and then do some magic to get the text, but I think that overriding data() for model can be a bit easier.
PPS: One obvious drawback is that Qt can rename QTipLabel class in the future. But I would not be worry about it. That won't happen becaus ethey do not change QtWidgets module any more. And if it happens, then you just rename the class in your code. No problem.
PPPS: Another potential corner-case is that some other widget (whose tooltip you do NOT want to capture with that shortcut) actually has the same tooltip text as any of the items in your list view (which you DO want to capture). Then if you display tooltip for your list item, then you move your mouse over to that other widget and hover so that its tooltip gets shown (but you do NOT want to capture it) and then you press that shortcut... But I guess that in reality this will not be your case. I doubt there will be this unlikely clash of tooltips.
With thanks to #V.K., this is what worked:
auto candidates = qApp->topLevelWidgets();
QString selectionText;
for (const auto & candidate : candidates)
{
if (strcmp(candidate->metaObject()->className(), "QTipLabel") == 0)
{
QLabel * label = qobject_cast<QLabel *>(candidate);
if (label->isVisible())
{
selectionText = label -> text();
break;
}
}
}
if (!selectionText.isEmpty())
QGuiApplication::clipboard() -> setText(selectionText);
There are two drop-downs. I'm trying to click on an item in a drop-down from a QComboBox.
For this purpose I created a function, launched for both drop-downs, here's an excerpt:
constexpr int DELAY{ 1000 };
void clickDropDown(int row, QComboBox *comboBox)
{
QListView *dropDownList = comboBox->findChild<QListView *>();
QModelIndex foundIndex{ dropDownList->model()->index(row, 0) };
QRect foundDropDownItem = dropDownList->visualRect(foundIndex);
QPoint foundDropDownItemPosition = foundDropDownItem.center();
QWidget *activeWidget = dropDownList->viewport();
QTest::mouseClick(activeWidget, Qt::LeftButton, Qt::NoModifier, foundDropDownItemPosition);
QTest::qWait(DELAY); // waits 1 second
}
Now the flow looks like this:
First drop-down list is shown,
The item is highlighted (mouseClick) as chosen, but not really selected, not chosen
UI test goes to the second column, the first column shows the first element in the list (i.e., the upper-most), despite what was highlighted;
An item in the second drop-down is selected/chosen
So, the second list seems to be working with this function, the first one doesn't. I need these items to be selected, not just highlighted.
I run on Ubuntu 21.04. Seems to work well on Windows 10. Seems to fail on Mac. Any suggestions how to make it work?
What works:
two clicks + Enter, but this will crash on MacOs. So that's not really a solution.
Also, it destroys the dropDownList object, and if make with an interval, will lead to a crash.
What else doesn't work: key down N times.
Any suggestions?
I found the answer by myself.
That's Qt's bug (as of Fall 2021), described here:
https://bugreports.qt.io/browse/QTBUG-77772. The mouse clicked not the button, but some point nearby. Why it was selected and why it failed to react otherwise is still a mystery.
Decision: I left this test to run on Windows and Linux only, closing it for Mac.
I have a TableView for which I've defined my own itemDelegate. Now, from within this delegate I can access the value for the column using styleData.value, but I'd also need to access the other properties in this same item but I can't find how to.
I need this, because the text styling needs to change depending on some other property of the item model.
Any ideas? thanks!
There is some documentation missing. Within the item delegate you can access the following (taken from the source code of TreeView.qml):
styleData (see documentation)
model (currently not documented)
modelData (currently not documented, not sure about this but I guess it's similar to ListView)
(By the way, what's also missing in the documentation but which is useful is styleData.role. Also, the documentation of the other delegates lacks some available properties too; the best is to peek into the source code of the QML file and have a look for the Loader element which instantiates your delegate. As a plus you learn how that creepy stuff works. ;))
With model and the row/column information you can then navigate to the item data. This code depends on the type of model.
If you're using QML's ListModel, then you can use model.get: model.get(styleData.row)[styleData.role] should then work (untested since I use it rarely, please give feedback).
If you're using a C++ QAbstractItemModel or friends, the best is to add a slot to the model class which takes just the row and role name, since that's the information the TableView works with (nor with role numbers nor with columns...).
However in both cases you shouldn't use the expression in a property binding! The notification system will not work since you don't use the property system for accessing the data. According to your question, I guess you wanted to use it in a expression with binding. I don't know how to properly listen to changes in the model manually.
An alternative approach is to access the other items of the row and provide a property there. Some hints:
From within one item, you can access other items of the same row by walking the object tree up twice (first to the Loader which instantiates your component, then to the actual row) and then down twice (first to the particular child object which is a Loader, then its instantiated item). You need to know the column number you want to access (not the role name), I assume you want to access the first column (index 0):
parent.parent.children[0].item
You can provide the model data using a property in each item. Assuming a simple Text element this might be:
Text {
property variant value: styleData.value // <-- Here you make it available
// your other stuff
}
Putting them together could look like the following. In this example I assume the first row contains an integer, and if it is zero, the second column should be red.
// (within TableView)
itemDelegate: Text {
property variant value: styleData.value
text: styleData.value
color: (styleData.column == 1 && parent.parent.children[0].item.value === 0)
"red" : "black"
}
I think it's pretty easy if you read the source code of TableViewItemDelegateLoader.qml (it is a private code in qtquickcontrol)
To access any role you use use : model[your_role_name] .
For exp: model["comment"]
Faced with same problem today, this is result of my investigations (Qt 5.2.x)
If you have hard limit to TableView, there is only one correct solution - use model.get(styleData.row)["roleForStyling"] as #leemes wrote. But it will very slow if you have big amount of data in model and using, for example, proxy model for sorting/filtering.
Direct solution from #leemes answer is great, but in general case not be working, because in TableView any Item wrapped in Loader and therefore independent from parent and other items:
When some item is created (where you want to change text style)
another element (from which to receive identity) cannot yet be
created
You may not have "parent" on item creation (i.e. binding will
be broken)
In my case, the best solution for deep customise was creation of the simple wrapper for ListView. In this case you have access for complete row data in delegate without the overhead. Highlights for making component ("My own ListView as table"):
Create standalone header (Rectangle or Item) - do not use header form ListView.This make it fixed for any amount of data.
Wrap ListView to ScrollView (if you need scrollbars)
Use Clip: true property in list for make correct
Set style for highlight and set highlightFollowsCurrentItem:true in ListView
As bonus in future this may be used for make "TreeTable" :)
I am working in Qt4.7, and I have a QListWidget in my dialog. I have a QString that needs to match the current text in the row of this widget (the individual rows are editable). Looking at the signals associated with QListWidget, there seem to be signals for when a different index is selected but none for when the text of a the currently selected row changes. I thought currentTextChanged(QString) would do it, but it didn't. I also thought to try to connect each individual row to something, but QListWidgetItem doesn't have any built-in signals. Does anyone know of a way to do this? Thanks!
At first it seems like QListWidget::itemChanged is the way to go, but soon you run into a problem: the signal is sent for everything - inserts, changing colors, checking boxes, and anything else that "changes" the item! Predelnik pointed that out in his answer. Some people have tried to put in flags and filter everywhere by intercepting various signals to find out if editing was the actual event. It gets very messy.
There is also QAbstractItemModel::dataChanged , which would seem like a good solution. It even has a parameter "const QVector& lstRoles" so you could scan for Qt::EditRole and see if it was really edited. Alas, there's a catch - it gets called for everything just like QListWidget::itemChanged and unfortunately, for QListWidget anyway, the roles parameter is always empty when it's called (I tried it). So much for that idea...
Fortunately, there's still hope... This solution does the trick! :
http://falsinsoft.blogspot.com/2013/11/qlistwidget-and-item-edit-event.html
He uses QAbstractItemDelegate::closeEditor, but I prefer using QAbstractItemDelegate::commitData.
So make a connect like so...
connect(ui.pLstItems->itemDelegate(), &QAbstractItemDelegate::commitData, this, &MyWidget::OnLstItemsCommitData);
Then implement the slot like this...
void MyWidget::OnLstItemsCommitData(QWidget* pLineEdit)
{
QString strNewText = reinterpret_cast<QLineEdit*>(pLineEdit)->text();
int nRow = ui.pLstItems->currentRow();
// do whatever you need here....
}
Now you have a slot that gets called only when the list item's text has been edited!
I guess you need to look into the following signal:
void QListWidget::itemChanged(QListWidgetItem * item)
But be careful because it's being sent every time some property of item changed, not only text. I remember when we ran into the problem once when we changed item colors and got tons of false positive slots called because of that. If you need more fine tuning I guess it's better to write model/view classes yourself and not rely on QListWidget.
I have designed a user interface by using Qt Designer, and I have set the tab order using the "edit tab order" mode.
Now what I'd like to know (for an other reason, not so important) is how to get the tab order of a specific QWidget in the ui?
I mean if I have several widgets, and say the tab order has been set, is there a way to do something like :
int nb = widget1->getTabOrder();
There is no way to get the tab order as an integer.
If you look into the C++ code that the uic tool creates from your ui file, it will call QWidget::setTabOrder() a few times, and that method just takes two QWidget pointers. Thus, Qt internally doesn't even store the tab order as an integer, but rather as a chained list of QWidget pointers.
You can query that chained list with QWidget::nextInFocusChain() and QWidget::previousInFocusChain(). This gives you the whole focus chain of the widget, containing all child widgets inside it, in the right order. Then you can get the real tab order list by checking their focusPolicy, enabled state and visible state, just like the inside implementation of the QWidget::focusNextPrevChild() function. If you really need an integer index here, you need to devise an algorithm yourself that calculates indices from that obtained tab order list.
(A bit late.) I had an a-ha moment: it's actually not at all difficult to determine the position of a widget in the tab sequence. It requires the use of Dynamic Properties, which allow you to "annotate" any QObject. The (default) focus list is simply a circular linked list with no distinguished (that I've seen identified) node. The function below annotates all the items in that linked list with a sequence number starting at the distinguished node (your choice) and provides a pointer to that in the parent widget/dialog.
Call it from your setupUi (etc.). (After any changes you may make to the focus sequence!) The parameters are the widget/dialog you want to sequence (and find the distinguished node in) and the widget you've decided should be "first" (distinguished).
// Add sequence numbers in the tab focus list starting at distinguishedNode
void sequenceFocus(QWidget *root, QWidget* distinguishedNode)
{
QVariant v;
v.setValue(distinguishedNode);
root->setProperty("focusRoot", v);
int itemCtr = 0;
QWidget* i = distinguishedNode;
do {
i->setProperty("focusPosition", itemCtr);
i = i->nextInFocusChain();
itemCtr++;
} while (i != distinguishedNode);
}
You can then get the distinguished (first) item from the list from the parent with:
QWidget* start = activeDialog->property("focusRoot").value<QWidget*>();
And get the sequence position of a widget with:
my_widget->property("focusPosition").toInt()
Note that (at least) Designer ends up putting more entries in the focus list than just those marked in the focus sequence as seen in Designer. The actual focusable widgets will be sparsely numbered. (Add debugging printouts in the function above to see everything.)