QComboBox Class▲
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Header: QComboBox
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CMake:
find_package(Qt6 REQUIRED COMPONENTS Widgets)
target_link_libraries(mytarget PRIVATE Qt6::Widgets)
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qmake: QT += widgets
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Inherits: QWidget
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Inherited By: QFontComboBox
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Group: QComboBox is part of basicwidgets
Detailed Description▲
A QComboBox provides a means of presenting a list of options to the user in a way that takes up the minimum amount of screen space.
A combobox is a selection widget that displays the current item, and can pop up a list of selectable items. A combobox may be editable, allowing the user to modify each item in the list.
Comboboxes can contain pixmaps as well as strings; the insertItem() and setItemText() functions are suitably overloaded. For editable comboboxes, the function clearEditText() is provided, to clear the displayed string without changing the combobox's contents.
There are three signals emitted if the current item of a combobox changes, currentIndexChanged(), currentTextChanged() and activated(). currentIndexChanged() and currentTextChanged() are always emitted regardless if the change was done programmatically or by user interaction, while activated() is only emitted when the change is caused by user interaction. The highlighted() signal is emitted when the user highlights an item in the combobox popup list. All three signals exist in two versions, one with a QString argument and one with an int argument. If the user selects or highlights a pixmap, only the int signals are emitted. Whenever the text of an editable combobox is changed the editTextChanged() signal is emitted.
When the user enters a new string in an editable combobox, the widget may or may not insert it, and it can insert it in several locations. The default policy is InsertAtBottom but you can change this using setInsertPolicy().
It is possible to constrain the input to an editable combobox using QValidator; see setValidator(). By default, any input is accepted.
A combobox can be populated using the insert functions, insertItem() and insertItems() for example. Items can be changed with setItemText(). An item can be removed with removeItem() and all items can be removed with clear(). The text of the current item is returned by currentText(), and the text of a numbered item is returned with text(). The current item can be set with setCurrentIndex(). The number of items in the combobox is returned by count(); the maximum number of items can be set with setMaxCount(). You can allow editing using setEditable(). For editable comboboxes you can set auto-completion using setCompleter() and whether or not the user can add duplicates is set with setDuplicatesEnabled().
QComboBox uses the model/view framework for its popup list and to store its items. By default a QStandardItemModel stores the items and a QListView subclass displays the popuplist. You can access the model and view directly (with model() and view()), but QComboBox also provides functions to set and get item data (e.g., setItemData() and itemText()). You can also set a new model and view (with setModel() and setView()). For the text and icon in the combobox label, the data in the model that has the Qt::DisplayRole and Qt::DecorationRole is used. Note that you cannot alter the SelectionMode of the view(), e.g., by using setSelectionMode().
See Also▲
See also QLineEdit, QSpinBox, QRadioButton, QButtonGroup
Member Type Documentation▲
enum QComboBox::InsertPolicy▲
This enum specifies what the QComboBox should do when a new string is entered by the user.
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Constant |
Value |
Description |
|---|---|---|
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QComboBox::NoInsert |
0 |
The string will not be inserted into the combobox. |
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QComboBox::InsertAtTop |
1 |
The string will be inserted as the first item in the combobox. |
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QComboBox::InsertAtCurrent |
2 |
The current item will be replaced by the string. |
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QComboBox::InsertAtBottom |
3 |
The string will be inserted after the last item in the combobox. |
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QComboBox::InsertAfterCurrent |
4 |
The string is inserted after the current item in the combobox. |
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QComboBox::InsertBeforeCurrent |
5 |
The string is inserted before the current item in the combobox. |
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QComboBox::InsertAlphabetically |
6 |
The string is inserted in the alphabetic order in the combobox. |
enum QComboBox::SizeAdjustPolicy▲
This enum specifies how the size hint of the QComboBox should adjust when new content is added or content changes.
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Constant |
Value |
Description |
|---|---|---|
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QComboBox::AdjustToContents |
0 |
The combobox will always adjust to the contents |
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QComboBox::AdjustToContentsOnFirstShow |
1 |
The combobox will adjust to its contents the first time it is shown. |
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QComboBox::AdjustToMinimumContentsLengthWithIcon |
2 |
The combobox will adjust to minimumContentsLength plus space for an icon. For performance reasons use this policy on large models. |
Property Documentation▲
[read-only] count : const int▲
This property holds the number of items in the combobox
By default, for an empty combo box, this property has a value of 0.
Access functions:
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int count() const
[read-only, since 5.2] currentData : const QVariant▲
This property holds the data for the current item
By default, for an empty combo box or a combo box in which no current item is set, this property contains an invalid QVariant.
This property was introduced in Qt 5.2.
Access functions:
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currentData(int role = Qt::UserRole) const
currentIndex : int▲
This property holds the index of the current item in the combobox.
The current index can change when inserting or removing items.
By default, for an empty combo box or a combo box in which no current item is set, this property has a value of -1.
Access functions:
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int currentIndex() const
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void setCurrentIndex(int index)
Notifier signal:
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void currentIndexChanged(int index)
currentText : QString▲
This property holds the current text
If the combo box is editable, the current text is the value displayed by the line edit. Otherwise, it is the value of the current item or an empty string if the combo box is empty or no current item is set.
The setter setCurrentText() simply calls setEditText() if the combo box is editable. Otherwise, if there is a matching text in the list, currentIndex is set to the corresponding index.
Access functions:
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currentText() const
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void setCurrentText(const &text)
Notifier signal:
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void currentTextChanged(const &text)
See Also▲
See also editable, setEditText()
duplicatesEnabled : bool▲
This property holds whether the user can enter duplicate items into the combobox
Note that it is always possible to programmatically insert duplicate items into the combobox.
By default, this property is false (duplicates are not allowed).
Access functions:
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bool duplicatesEnabled() const
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void setDuplicatesEnabled(bool enable)
editable : bool▲
This property holds whether the combo box can be edited by the user
By default, this property is false. The effect of editing depends on the insert policy.
When disabling the editable state, the validator and completer are removed.
Access functions:
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bool isEditable() const
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void setEditable(bool editable)
See Also▲
See also InsertPolicy
frame : bool▲
This property holds whether the combo box draws itself with a frame
If enabled (the default) the combo box draws itself inside a frame, otherwise the combo box draws itself without any frame.
Access functions:
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bool hasFrame() const
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void setFrame(bool)
iconSize : QSize▲
This property holds the size of the icons shown in the combobox.
Unless explicitly set this returns the default value of the current style. This size is the maximum size that icons can have; icons of smaller size are not scaled up.
Access functions:
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iconSize() const
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void setIconSize(const &size)
insertPolicy : InsertPolicy▲
This property holds the policy used to determine where user-inserted items should appear in the combobox
The default value is InsertAtBottom, indicating that new items will appear at the bottom of the list of items.
Access functions:
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insertPolicy() const
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void setInsertPolicy( policy)
See Also▲
See also InsertPolicy
maxCount : int▲
This property holds the maximum number of items allowed in the combobox
If you set the maximum number to be less then the current amount of items in the combobox, the extra items will be truncated. This also applies if you have set an external model on the combobox.
By default, this property's value is derived from the highest signed integer available (typically 2147483647).
Access functions:
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int maxCount() const
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void setMaxCount(int max)
maxVisibleItems : int▲
This property holds the maximum allowed size on screen of the combo box, measured in items
By default, this property has a value of 10.
This property is ignored for non-editable comboboxes in styles that returns true for QStyle::SH_ComboBox_Popup such as the Mac style or the Gtk+ Style.
Access functions:
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int maxVisibleItems() const
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void setMaxVisibleItems(int maxItems)
minimumContentsLength : int▲
This property holds the minimum number of characters that should fit into the combobox.
The default value is 0.
If this property is set to a positive value, the minimumSizeHint() and sizeHint() take it into account.
Access functions:
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int minimumContentsLength() const
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void setMinimumContentsLength(int characters)
See Also▲
See also sizeAdjustPolicy
modelColumn : int▲
This property holds the column in the model that is visible.
If set prior to populating the combo box, the pop-up view will not be affected and will show the first column (using this property's default value).
By default, this property has a value of 0.
In an editable combobox, the visible column will also become the completion column.
Access functions:
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int modelColumn() const
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void setModelColumn(int visibleColumn)
[since 5.15] placeholderText : QString▲
Sets a placeholderText text shown when no valid index is set
The placeholderText will be shown when an invalid index is set. The text is not accessible in the dropdown list. When this function is called before items are added the placeholder text will be shown, otherwise you have to call setCurrentIndex(-1) programmatically if you want to show the placeholder text. Set an empty placeholder text to reset the setting.
When the QComboBox is editable, use QLineEdit::setPlaceholderText() instead.
This property was introduced in Qt 5.15.
Access functions:
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placeholderText() const
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void setPlaceholderText(const &placeholderText)
sizeAdjustPolicy : SizeAdjustPolicy▲
This property holds the policy describing how the size of the combobox changes when the content changes
The default value is AdjustToContentsOnFirstShow.
Access functions:
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sizeAdjustPolicy() const
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void setSizeAdjustPolicy( policy)
See Also▲
See also SizeAdjustPolicy
Member Function Documentation▲
[explicit] QComboBox::QComboBox(QWidget *parent = nullptr)▲
Constructs a combobox with the given parent, using the default model QStandardItemModel.
[virtual] QComboBox::~QComboBox()▲
Destroys the combobox.
void QComboBox::activated(int index)▲
This signal is sent when the user chooses an item in the combobox. The item's index is passed. Note that this signal is sent even when the choice is not changed. If you need to know when the choice actually changes, use signal currentIndexChanged() or currentTextChanged().
void QComboBox::addItem(const QString &text, const QVariant &userData = QVariant())▲
Adds an item to the combobox with the given text, and containing the specified userData (stored in the Qt::UserRole). The item is appended to the list of existing items.
void QComboBox::addItem(const QIcon &icon, const QString &text, const QVariant &userData = QVariant())▲
Adds an item to the combobox with the given icon and text, and containing the specified userData (stored in the Qt::UserRole). The item is appended to the list of existing items.
void QComboBox::addItems(const QStringList &texts)▲
Adds each of the strings in the given texts to the combobox. Each item is appended to the list of existing items in turn.
[override virtual protected] void QComboBox::changeEvent(QEvent *e)▲
Reimplements: QWidget::changeEvent(QEvent *event).
void QComboBox::clear()▲
Clears the combobox, removing all items.
Note: If you have set an external model on the combobox this model will still be cleared when calling this function.
void QComboBox::clearEditText()▲
Clears the contents of the line edit used for editing in the combobox.
QCompleter *QComboBox::completer() const▲
Returns the completer that is used to auto complete text input for the combobox.
See Also▲
See also setCompleter(), editable
[override virtual protected] void QComboBox::contextMenuEvent(QContextMenuEvent *e)▲
Reimplements: QWidget::contextMenuEvent(QContextMenuEvent *event).
void QComboBox::currentIndexChanged(int index)▲
This signal is sent whenever the currentIndex in the combobox changes either through user interaction or programmatically. The item's index is passed or -1 if the combobox becomes empty or the currentIndex was reset.
Notifier signal for property currentIndex.
[since 5.0] void QComboBox::currentTextChanged(const QString &text)▲
This signal is sent whenever currentText changes. The new value is passed as text.
Notifier signal for property currentText.
This function was introduced in Qt 5.0.
void QComboBox::editTextChanged(const QString &text)▲
This signal is emitted when the text in the combobox's line edit widget is changed. The new text is specified by text.
[override virtual] bool QComboBox::event(QEvent *event)▲
Reimplements: QWidget::event(QEvent *event).
int QComboBox::findData(const QVariant &data, int role = Qt::UserRole, Qt::MatchFlags flags = static_cast<Qt::MatchFlags>(Qt::MatchExactly|Qt::MatchCaseSensitive)) const▲
Returns the index of the item containing the given data for the given role; otherwise returns -1.
The flags specify how the items in the combobox are searched.
int QComboBox::findText(const QString &text, Qt::MatchFlags flags = Qt::MatchExactly|Qt::MatchCaseSensitive) const▲
Returns the index of the item containing the given text; otherwise returns -1.
The flags specify how the items in the combobox are searched.
[override virtual protected] void QComboBox::focusInEvent(QFocusEvent *e)▲
Reimplements: QWidget::focusInEvent(QFocusEvent *event).
[override virtual protected] void QComboBox::focusOutEvent(QFocusEvent *e)▲
Reimplements: QWidget::focusOutEvent(QFocusEvent *event).
[override virtual protected] void QComboBox::hideEvent(QHideEvent *e)▲
Reimplements: QWidget::hideEvent(QHideEvent *event).
[virtual] void QComboBox::hidePopup()▲
Hides the list of items in the combobox if it is currently visible and resets the internal state, so that if the custom pop-up was shown inside the reimplemented showPopup(), then you also need to reimplement the hidePopup() function to hide your custom pop-up and call the base class implementation to reset the internal state whenever your custom pop-up widget is hidden.
See Also▲
See also showPopup()
void QComboBox::highlighted(int index)▲
This signal is sent when an item in the combobox popup list is highlighted by the user. The item's index is passed.
[virtual protected] void QComboBox::initStyleOption(QStyleOptionComboBox *option) const▲
Initialize option with the values from this QComboBox. This method is useful for subclasses when they need a QStyleOptionComboBox, but don't want to fill in all the information themselves.
See Also▲
See also QStyleOption::initFrom()
[override virtual protected] void QComboBox::inputMethodEvent(QInputMethodEvent *e)▲
Reimplements: QWidget::inputMethodEvent(QInputMethodEvent *event).
[override virtual] QVariant QComboBox::inputMethodQuery(Qt::InputMethodQuery query) const▲
Reimplements: QWidget::inputMethodQuery(Qt::InputMethodQuery query) const.
void QComboBox::insertItem(int index, const QString &text, const QVariant &userData = QVariant())▲
Inserts the text and userData (stored in the Qt::UserRole) into the combobox at the given index.
If the index is equal to or higher than the total number of items, the new item is appended to the list of existing items. If the index is zero or negative, the new item is prepended to the list of existing items.
See Also▲
See also insertItems()
void QComboBox::insertItem(int index, const QIcon &icon, const QString &text, const QVariant &userData = QVariant())▲
Inserts the icon, text and userData (stored in the Qt::UserRole) into the combobox at the given index.
If the index is equal to or higher than the total number of items, the new item is appended to the list of existing items. If the index is zero or negative, the new item is prepended to the list of existing items.
See Also▲
See also insertItems()
void QComboBox::insertItems(int index, const QStringList &list)▲
Inserts the strings from the list into the combobox as separate items, starting at the index specified.
If the index is equal to or higher than the total number of items, the new items are appended to the list of existing items. If the index is zero or negative, the new items are prepended to the list of existing items.
See Also▲
See also insertItem()
void QComboBox::insertSeparator(int index)▲
Inserts a separator item into the combobox at the given index.
If the index is equal to or higher than the total number of items, the new item is appended to the list of existing items. If the index is zero or negative, the new item is prepended to the list of existing items.
See Also▲
See also insertItem()
QVariant QComboBox::itemData(int index, int role = Qt::UserRole) const▲
Returns the data for the given role in the given index in the combobox, or an invalid QVariant if there is no data for this role.
See Also▲
See also setItemData()
QAbstractItemDelegate *QComboBox::itemDelegate() const▲
QIcon QComboBox::itemIcon(int index) const▲
QString QComboBox::itemText(int index) const▲
[override virtual protected] void QComboBox::keyPressEvent(QKeyEvent *e)▲
Reimplements: QWidget::keyPressEvent(QKeyEvent *event).
[override virtual protected] void QComboBox::keyReleaseEvent(QKeyEvent *e)▲
Reimplements: QWidget::keyReleaseEvent(QKeyEvent *event).
QLineEdit *QComboBox::lineEdit() const▲
Returns the line edit used to edit items in the combobox, or nullptr if there is no line edit.
Only editable combo boxes have a line edit.
See Also▲
See also setLineEdit()
[override virtual] QSize QComboBox::minimumSizeHint() const▲
Reimplements an access function for property: QWidget::minimumSizeHint.
QAbstractItemModel *QComboBox::model() const▲
[override virtual protected] void QComboBox::mousePressEvent(QMouseEvent *e)▲
Reimplements: QWidget::mousePressEvent(QMouseEvent *event).
[override virtual protected] void QComboBox::mouseReleaseEvent(QMouseEvent *e)▲
Reimplements: QWidget::mouseReleaseEvent(QMouseEvent *event).
[override virtual protected] void QComboBox::paintEvent(QPaintEvent *e)▲
Reimplements: QWidget::paintEvent(QPaintEvent *event).
void QComboBox::removeItem(int index)▲
Removes the item at the given index from the combobox. This will update the current index if the index is removed.
This function does nothing if index is out of range.
[override virtual protected] void QComboBox::resizeEvent(QResizeEvent *e)▲
Reimplements: QWidget::resizeEvent(QResizeEvent *event).
QModelIndex QComboBox::rootModelIndex() const▲
Returns the root model item index for the items in the combobox.
See Also▲
See also setRootModelIndex()
void QComboBox::setCompleter(QCompleter *completer)▲
Sets the completer to use instead of the current completer. If completer is nullptr, auto completion is disabled.
By default, for an editable combo box, a QCompleter that performs case insensitive inline completion is automatically created.
The completer is removed when the editable property becomes false, or when the line edit is replaced by a call to setLineEdit(). Setting a completer on a QComboBox that is not editable will be ignored.
See Also▲
See also completer()
void QComboBox::setEditText(const QString &text)▲
Sets the text in the combobox's text edit.
void QComboBox::setItemData(int index, const QVariant &value, int role = Qt::UserRole)▲
Sets the data role for the item on the given index in the combobox to the specified value.
See Also▲
See also itemData()
void QComboBox::setItemDelegate(QAbstractItemDelegate *delegate)▲
Sets the item delegate for the popup list view. The combobox takes ownership of the delegate.
Any existing delegate will be removed, but not deleted. QComboBox does not take ownership of delegate.
You should not share the same instance of a delegate between comboboxes, widget mappers or views. Doing so can cause incorrect or unintuitive editing behavior since each view connected to a given delegate may receive the closeEditor() signal, and attempt to access, modify or close an editor that has already been closed.
See Also▲
See also itemDelegate()
void QComboBox::setItemIcon(int index, const QIcon &icon)▲
void QComboBox::setItemText(int index, const QString &text)▲
void QComboBox::setLineEdit(QLineEdit *edit)▲
Sets the line edit to use instead of the current line edit widget.
The combo box takes ownership of the line edit.
Since the combobox's line edit owns the QCompleter, any previous call to setCompleter() will no longer have any effect.
See Also▲
See also lineEdit()
[virtual] void QComboBox::setModel(QAbstractItemModel *model)▲
Sets the model to be model. model must not be nullptr. If you want to clear the contents of a model, call clear().
If the combobox is editable, then the model will also be set on the completer of the line edit.
See Also▲
See also model(), clear(), setCompleter()
void QComboBox::setRootModelIndex(const QModelIndex &index)▲
void QComboBox::setValidator(const QValidator *validator)▲
Sets the validator to use instead of the current validator.
The validator is removed when the editable property becomes false.
See Also▲
See also validator()
void QComboBox::setView(QAbstractItemView *itemView)▲
Sets the view to be used in the combobox popup to the given itemView. The combobox takes ownership of the view.
Note: If you want to use the convenience views (like QListWidget, QTableWidget or QTreeWidget), make sure to call setModel() on the combobox with the convenience widgets model before calling this function.
See Also▲
See also view()
[override virtual protected] void QComboBox::showEvent(QShowEvent *e)▲
Reimplements: QWidget::showEvent(QShowEvent *event).
[virtual] void QComboBox::showPopup()▲
Displays the list of items in the combobox. If the list is empty then no items will be shown.
If you reimplement this function to show a custom pop-up, make sure you call hidePopup() to reset the internal state.
See Also▲
See also hidePopup()
[override virtual] QSize QComboBox::sizeHint() const▲
Reimplements an access function for property: QWidget::sizeHint.
This implementation caches the size hint to avoid resizing when the contents change dynamically. To invalidate the cached value change the sizeAdjustPolicy.
[since 5.14] void QComboBox::textActivated(const QString &text)▲
This signal is sent when the user chooses an item in the combobox. The item's text is passed. Note that this signal is sent even when the choice is not changed. If you need to know when the choice actually changes, use signal currentIndexChanged() or currentTextChanged().
This function was introduced in Qt 5.14.
[since 5.14] void QComboBox::textHighlighted(const QString &text)▲
This signal is sent when an item in the combobox popup list is highlighted by the user. The item's text is passed.
This function was introduced in Qt 5.14.
const QValidator *QComboBox::validator() const▲
Returns the validator that is used to constrain text input for the combobox.
See Also▲
See also setValidator(), editable
QAbstractItemView *QComboBox::view() const▲
[override virtual protected] void QComboBox::wheelEvent(QWheelEvent *e)▲
Reimplements: QWidget::wheelEvent(QWheelEvent *event).