QLineEdit Class

The QLineEdit widget is a one-line text editor. More...

Header:	#include <QLineEdit>
qmake:	QT += widgets
Inherits:	QWidget

• List of all members, including inherited members
• Obsolete members

Public Types

enum	ActionPosition { LeadingPosition, TrailingPosition }
enum	EchoMode { Normal, NoEcho, Password, PasswordEchoOnEdit }

Properties

acceptableInput : const bool alignment : Qt::Alignment clearButtonEnabled : bool cursorMoveStyle : Qt::CursorMoveStyle cursorPosition : int displayText : const QString dragEnabled : bool echoMode : EchoMode frame : bool hasSelectedText : const bool

inputMask : QString maxLength : int modified : bool placeholderText : QString readOnly : bool redoAvailable : const bool selectedText : const QString text : QString undoAvailable : const bool

Public Functions

	QLineEdit(const QString &contents, QWidget *parent = nullptr)
	QLineEdit(QWidget *parent = nullptr)
virtual	~QLineEdit()
void	addAction(QAction *action, QLineEdit::ActionPosition position)
QAction *	addAction(const QIcon &icon, QLineEdit::ActionPosition position)
Qt::Alignment	alignment() const
void	backspace()
QCompleter *	completer() const
QMenu *	createStandardContextMenu()
void	cursorBackward(bool mark, int steps = 1)
void	cursorForward(bool mark, int steps = 1)
Qt::CursorMoveStyle	cursorMoveStyle() const
int	cursorPosition() const
int	cursorPositionAt(const QPoint &pos)
void	cursorWordBackward(bool mark)
void	cursorWordForward(bool mark)
void	del()
void	deselect()
QString	displayText() const
bool	dragEnabled() const
QLineEdit::EchoMode	echoMode() const
void	end(bool mark)
bool	hasAcceptableInput() const
bool	hasFrame() const
bool	hasSelectedText() const
void	home(bool mark)
QString	inputMask() const
void	insert(const QString &newText)
bool	isClearButtonEnabled() const
bool	isModified() const
bool	isReadOnly() const
bool	isRedoAvailable() const
bool	isUndoAvailable() const
int	maxLength() const
QString	placeholderText() const
QString	selectedText() const
int	selectionEnd() const
int	selectionLength() const
int	selectionStart() const
void	setAlignment(Qt::Alignment flag)
void	setClearButtonEnabled(bool enable)
void	setCompleter(QCompleter *c)
void	setCursorMoveStyle(Qt::CursorMoveStyle style)
void	setCursorPosition(int)
void	setDragEnabled(bool b)
void	setEchoMode(QLineEdit::EchoMode)
void	setFrame(bool)
void	setInputMask(const QString &inputMask)
void	setMaxLength(int)
void	setModified(bool)
void	setPlaceholderText(const QString &)
void	setReadOnly(bool)
void	setSelection(int start, int length)
void	setTextMargins(int left, int top, int right, int bottom)
void	setTextMargins(const QMargins &margins)
void	setValidator(const QValidator *v)
QString	text() const
QMargins	textMargins() const
const QValidator *	validator() const

Reimplemented Public Functions

virtual bool	event(QEvent *e) override
virtual QVariant	inputMethodQuery(Qt::InputMethodQuery property) const override
virtual QSize	minimumSizeHint() const override
virtual QSize	sizeHint() const override

Public Slots

void	clear()
void	copy() const
void	cut()
void	paste()
void	redo()
void	selectAll()
void	setText(const QString &)
void	undo()

Signals

void	cursorPositionChanged(int oldPos, int newPos)
void	editingFinished()
void	inputRejected()
void	returnPressed()
void	selectionChanged()
void	textChanged(const QString &text)
void	textEdited(const QString &text)

Protected Functions

QRect	cursorRect() const
void	initStyleOption(QStyleOptionFrame *option) const

Reimplemented Protected Functions

virtual void	changeEvent(QEvent *ev) override
virtual void	contextMenuEvent(QContextMenuEvent *event) override
virtual void	dragEnterEvent(QDragEnterEvent *e) override
virtual void	dragLeaveEvent(QDragLeaveEvent *e) override
virtual void	dragMoveEvent(QDragMoveEvent *e) override
virtual void	dropEvent(QDropEvent *e) override
virtual void	focusInEvent(QFocusEvent *e) override
virtual void	focusOutEvent(QFocusEvent *e) override
virtual void	inputMethodEvent(QInputMethodEvent *e) override
virtual void	keyPressEvent(QKeyEvent *event) override
virtual void	mouseDoubleClickEvent(QMouseEvent *e) override
virtual void	mouseMoveEvent(QMouseEvent *e) override
virtual void	mousePressEvent(QMouseEvent *e) override
virtual void	mouseReleaseEvent(QMouseEvent *e) override
virtual void	paintEvent(QPaintEvent *) override

Detailed Description

A line edit allows the user to enter and edit a single line of plain text with a useful collection of editing functions, including undo and redo, cut and paste, and drag and drop (see setDragEnabled()).

By changing the echoMode() of a line edit, it can also be used as a "write-only" field, for inputs such as passwords.

The length of the text can be constrained to maxLength(). The text can be arbitrarily constrained using a validator() or an inputMask(), or both. When switching between a validator and an input mask on the same line edit, it is best to clear the validator or input mask to prevent undefined behavior.

A related class is QTextEdit which allows multi-line, rich text editing.

You can change the text with setText() or insert(). The text is retrieved with text(); the displayed text (which may be different, see EchoMode) is retrieved with displayText(). Text can be selected with setSelection() or selectAll(), and the selection can be cut(), copy()ied and paste()d. The text can be aligned with setAlignment().

When the text changes the textChanged() signal is emitted; when the text changes other than by calling setText() the textEdited() signal is emitted; when the cursor is moved the cursorPositionChanged() signal is emitted; and when the Return or Enter key is pressed the returnPressed() signal is emitted.

When editing is finished, either because the line edit lost focus or Return/Enter is pressed the editingFinished() signal is emitted.

Note that if there is a validator set on the line edit, the returnPressed()/editingFinished() signals will only be emitted if the validator returns QValidator::Acceptable.

By default, QLineEdits have a frame as specified by platform style guides; you can turn it off by calling setFrame(false).

The default key bindings are described below. The line edit also provides a context menu (usually invoked by a right mouse click) that presents some of these editing options.

Keypress	Action
Left Arrow	Moves the cursor one character to the left.
Shift+Left Arrow	Moves and selects text one character to the left.
Right Arrow	Moves the cursor one character to the right.
Shift+Right Arrow	Moves and selects text one character to the right.
Home	Moves the cursor to the beginning of the line.
End	Moves the cursor to the end of the line.
Backspace	Deletes the character to the left of the cursor.
Ctrl+Backspace	Deletes the word to the left of the cursor.
Delete	Deletes the character to the right of the cursor.
Ctrl+Delete	Deletes the word to the right of the cursor.
Ctrl+A	Select all.
Ctrl+C	Copies the selected text to the clipboard.
Ctrl+Insert	Copies the selected text to the clipboard.
Ctrl+K	Deletes to the end of the line.
Ctrl+V	Pastes the clipboard text into line edit.
Shift+Insert	Pastes the clipboard text into line edit.
Ctrl+X	Deletes the selected text and copies it to the clipboard.
Shift+Delete	Deletes the selected text and copies it to the clipboard.
Ctrl+Z	Undoes the last operation.
Ctrl+Y	Redoes the last undone operation.

Any other key sequence that represents a valid character, will cause the character to be inserted into the line edit.

See also QTextEdit, QLabel, QComboBox, GUI Design Handbook: Field, Entry, and Line Edits Example.

Member Type Documentation

enum QLineEdit::ActionPosition

This enum type describes how a line edit should display the action widgets to be added.

Constant	Value	Description
QLineEdit::LeadingPosition	0	The widget is displayed to the left of the text when using layout direction Qt::LeftToRight or to the right when using Qt::RightToLeft, respectively.
QLineEdit::TrailingPosition	1	The widget is displayed to the right of the text when using layout direction Qt::LeftToRight or to the left when using Qt::RightToLeft, respectively.

This enum was introduced or modified in Qt 5.2.

See also addAction(), removeAction(), and QWidget::layoutDirection.

enum QLineEdit::EchoMode

This enum type describes how a line edit should display its contents.

Constant	Value	Description
QLineEdit::Normal	0	Display characters as they are entered. This is the default.
QLineEdit::NoEcho	1	Do not display anything. This may be appropriate for passwords where even the length of the password should be kept secret.
QLineEdit::Password	2	Display platform-dependent password mask characters instead of the characters actually entered.
QLineEdit::PasswordEchoOnEdit	3	Display characters as they are entered while editing otherwise display characters as with Password.

See also setEchoMode() and echoMode().

Member Function Documentation

QLineEdit::QLineEdit(const QString &contents, QWidget *parent = nullptr)

Constructs a line edit containing the text contents.

The cursor position is set to the end of the line and the maximum text length to 32767 characters.

The parent and argument is sent to the QWidget constructor.

See also text() and setMaxLength().

QLineEdit::QLineEdit(QWidget *parent = nullptr)

Constructs a line edit with no text.

The maximum text length is set to 32767 characters.

The parent argument is sent to the QWidget constructor.

See also setText() and setMaxLength().

[slot] void QLineEdit::clear()

Clears the contents of the line edit.

See also setText() and insert().

[slot] void QLineEdit::copy() const

Copies the selected text to the clipboard, if there is any, and if echoMode() is Normal.

See also cut() and paste().

[signal] void QLineEdit::cursorPositionChanged(int oldPos, int newPos)

This signal is emitted whenever the cursor moves. The previous position is given by oldPos, and the new position by newPos.

See also setCursorPosition() and cursorPosition().

[slot] void QLineEdit::cut()

Copies the selected text to the clipboard and deletes it, if there is any, and if echoMode() is Normal.

If the current validator disallows deleting the selected text, cut() will copy without deleting.

See also copy(), paste(), and setValidator().

[signal] void QLineEdit::editingFinished()

This signal is emitted when the Return or Enter key is pressed or the line edit loses focus. Note that if there is a validator() or inputMask() set on the line edit and enter/return is pressed, the editingFinished() signal will only be emitted if the input follows the inputMask() and the validator() returns QValidator::Acceptable.

[signal] void QLineEdit::inputRejected()

This signal is emitted when the user presses a key that is not considered to be acceptable input. For example, if a key press results in a validator's validate() call to return Invalid. Another case is when trying to enter in more characters beyond the maximum length of the line edit.

Note: This signal will still be emitted in a case where part of the text is accepted but not all of it is. For example, if there is a maximum length set and the clipboard text is longer than the maximum length when it is pasted.

This function was introduced in Qt 5.12.

[slot] void QLineEdit::paste()

Inserts the clipboard's text at the cursor position, deleting any selected text, providing the line edit is not read-only.

If the end result would be invalid to the current validator, nothing happens.

See also copy() and cut().

[slot] void QLineEdit::redo()

Redoes the last operation if redo is available.

[signal] void QLineEdit::returnPressed()

This signal is emitted when the Return or Enter key is pressed. Note that if there is a validator() or inputMask() set on the line edit, the returnPressed() signal will only be emitted if the input follows the inputMask() and the validator() returns QValidator::Acceptable.

[slot] void QLineEdit::selectAll()

Selects all the text (i.e. highlights it) and moves the cursor to the end. This is useful when a default value has been inserted because if the user types before clicking on the widget, the selected text will be deleted.

See also setSelection() and deselect().

[signal] void QLineEdit::selectionChanged()

This signal is emitted whenever the selection changes.

See also hasSelectedText() and selectedText().

[signal] void QLineEdit::textChanged(const QString &text)

This signal is emitted whenever the text changes. The text argument is the new text.

Unlike textEdited(), this signal is also emitted when the text is changed programmatically, for example, by calling setText().

Note: Notifier signal for property text.

[signal] void QLineEdit::textEdited(const QString &text)

This signal is emitted whenever the text is edited. The text argument is the new text.

Unlike textChanged(), this signal is not emitted when the text is changed programmatically, for example, by calling setText().

[slot] void QLineEdit::undo()

Undoes the last operation if undo is available. Deselects any current selection, and updates the selection start to the current cursor position.

[virtual] QLineEdit::~QLineEdit()

Destroys the line edit.

void QLineEdit::addAction(QAction *action, QLineEdit::ActionPosition position)

Adds the action to the list of actions at the position.

This function was introduced in Qt 5.2.

QAction *QLineEdit::addAction(const QIcon &icon, QLineEdit::ActionPosition position)

This is an overloaded function.

Creates a new action with the given icon at the position.

This function was introduced in Qt 5.2.

void QLineEdit::backspace()

If no text is selected, deletes the character to the left of the text cursor and moves the cursor one position to the left. If any text is selected, the cursor is moved to the beginning of the selected text and the selected text is deleted.

See also del().

[override virtual protected] void QLineEdit::changeEvent(QEvent *ev)

Reimplements: QWidget::changeEvent(QEvent *event).

QCompleter *QLineEdit::completer() const

Returns the current QCompleter that provides completions.

This function was introduced in Qt 4.2.

See also setCompleter().

[override virtual protected] void QLineEdit::contextMenuEvent(QContextMenuEvent *event)

Reimplements: QWidget::contextMenuEvent(QContextMenuEvent *event).

Shows the standard context menu created with createStandardContextMenu().

If you do not want the line edit to have a context menu, you can set its contextMenuPolicy to Qt::NoContextMenu. If you want to customize the context menu, reimplement this function. If you want to extend the standard context menu, reimplement this function, call createStandardContextMenu() and extend the menu returned.

void LineEdit::contextMenuEvent(QContextMenuEvent *event)
{
    QMenu *menu = createStandardContextMenu();
    menu->addAction(tr("My Menu Item"));
    //...
    menu->exec(event->globalPos());
    delete menu;
}

The event parameter is used to obtain the position where the mouse cursor was when the event was generated.

See also setContextMenuPolicy().

QMenu *QLineEdit::createStandardContextMenu()

This function creates the standard context menu which is shown when the user clicks on the line edit with the right mouse button. It is called from the default contextMenuEvent() handler. The popup menu's ownership is transferred to the caller.

void QLineEdit::cursorBackward(bool mark, int steps = 1)

Moves the cursor back steps characters. If mark is true each character moved over is added to the selection; if mark is false the selection is cleared.

See also cursorForward().

void QLineEdit::cursorForward(bool mark, int steps = 1)

Moves the cursor forward steps characters. If mark is true each character moved over is added to the selection; if mark is false the selection is cleared.

See also cursorBackward().

int QLineEdit::cursorPositionAt(const QPoint &pos)

Returns the cursor position under the point pos.

[protected] QRect QLineEdit::cursorRect() const

Returns a rectangle that includes the lineedit cursor.

This function was introduced in Qt 4.4.

void QLineEdit::cursorWordBackward(bool mark)

Moves the cursor one word backward. If mark is true, the word is also selected.

See also cursorWordForward().

void QLineEdit::cursorWordForward(bool mark)

Moves the cursor one word forward. If mark is true, the word is also selected.

See also cursorWordBackward().

void QLineEdit::del()

If no text is selected, deletes the character to the right of the text cursor. If any text is selected, the cursor is moved to the beginning of the selected text and the selected text is deleted.

See also backspace().

void QLineEdit::deselect()

Deselects any selected text.

See also setSelection() and selectAll().

[override virtual protected] void QLineEdit::dragEnterEvent(QDragEnterEvent *e)

Reimplements: QWidget::dragEnterEvent(QDragEnterEvent *event).

[override virtual protected] void QLineEdit::dragLeaveEvent(QDragLeaveEvent *e)

Reimplements: QWidget::dragLeaveEvent(QDragLeaveEvent *event).

[override virtual protected] void QLineEdit::dragMoveEvent(QDragMoveEvent *e)

Reimplements: QWidget::dragMoveEvent(QDragMoveEvent *event).

[override virtual protected] void QLineEdit::dropEvent(QDropEvent *e)

Reimplements: QWidget::dropEvent(QDropEvent *event).

void QLineEdit::end(bool mark)

Moves the text cursor to the end of the line unless it is already there. If mark is true, text is selected towards the last position; otherwise, any selected text is unselected if the cursor is moved.

See also home().

[override virtual] bool QLineEdit::event(QEvent *e)

Reimplements: QWidget::event(QEvent *event).

[override virtual protected] void QLineEdit::focusInEvent(QFocusEvent *e)

Reimplements: QWidget::focusInEvent(QFocusEvent *event).

[override virtual protected] void QLineEdit::focusOutEvent(QFocusEvent *e)

Reimplements: QWidget::focusOutEvent(QFocusEvent *event).

void QLineEdit::home(bool mark)

Moves the text cursor to the beginning of the line unless it is already there. If mark is true, text is selected towards the first position; otherwise, any selected text is unselected if the cursor is moved.

See also end().

[protected] void QLineEdit::initStyleOption(QStyleOptionFrame *option) const

Initialize option with the values from this QLineEdit. This method is useful for subclasses when they need a QStyleOptionFrame, but don't want to fill in all the information themselves.

See also QStyleOption::initFrom().

[override virtual protected] void QLineEdit::inputMethodEvent(QInputMethodEvent *e)

Reimplements: QWidget::inputMethodEvent(QInputMethodEvent *event).

[override virtual] QVariant QLineEdit::inputMethodQuery(Qt::InputMethodQuery property) const

Reimplements: QWidget::inputMethodQuery(Qt::InputMethodQuery query) const.

void QLineEdit::insert(const QString &newText)

Deletes any selected text, inserts newText, and validates the result. If it is valid, it sets it as the new contents of the line edit.

See also setText() and clear().

[override virtual protected] void QLineEdit::keyPressEvent(QKeyEvent *event)

Reimplements: QWidget::keyPressEvent(QKeyEvent *event).

Converts the given key press event into a line edit action.

If Return or Enter is pressed and the current text is valid (or can be made valid by the validator), the signal returnPressed() is emitted.

The default key bindings are listed in the class's detailed description.

[override virtual] QSize QLineEdit::minimumSizeHint() const

Reimplements an access function for property: QWidget::minimumSizeHint.

Returns a minimum size for the line edit.

The width returned is usually enough for at least one character.

[override virtual protected] void QLineEdit::mouseDoubleClickEvent(QMouseEvent *e)

Reimplements: QWidget::mouseDoubleClickEvent(QMouseEvent *event).

[override virtual protected] void QLineEdit::mouseMoveEvent(QMouseEvent *e)

Reimplements: QWidget::mouseMoveEvent(QMouseEvent *event).

[override virtual protected] void QLineEdit::mousePressEvent(QMouseEvent *e)

Reimplements: QWidget::mousePressEvent(QMouseEvent *event).

[override virtual protected] void QLineEdit::mouseReleaseEvent(QMouseEvent *e)

Reimplements: QWidget::mouseReleaseEvent(QMouseEvent *event).

[override virtual protected] void QLineEdit::paintEvent(QPaintEvent *)

Reimplements: QWidget::paintEvent(QPaintEvent *event).

int QLineEdit::selectionEnd() const

Returns the index of the character directly after the selection in the line edit or -1 if no text is selected.

This function was introduced in Qt 5.10.

See also selectedText(), selectionStart(), and selectionLength().

int QLineEdit::selectionLength() const

Returns the length of the selection.

This function was introduced in Qt 5.10.

See also selectedText(), selectionStart(), and selectionEnd().

int QLineEdit::selectionStart() const

Returns the index of the first selected character in the line edit or -1 if no text is selected.

See also selectedText(), selectionEnd(), and selectionLength().

void QLineEdit::setCompleter(QCompleter *c)

Sets this line edit to provide auto completions from the completer, c. The completion mode is set using QCompleter::setCompletionMode().

To use a QCompleter with a QValidator or QLineEdit::inputMask, you need to ensure that the model provided to QCompleter contains valid entries. You can use the QSortFilterProxyModel to ensure that the QCompleter's model contains only valid entries.

If c == 0, setCompleter() removes the current completer, effectively disabling auto completion.

This function was introduced in Qt 4.2.

See also completer() and QCompleter.

void QLineEdit::setSelection(int start, int length)

Selects text from position start and for length characters. Negative lengths are allowed.

See also deselect(), selectAll(), and selectedText().

void QLineEdit::setTextMargins(int left, int top, int right, int bottom)

Sets the margins around the text inside the frame to have the sizes left, top, right, and bottom.

See also textMargins().

This function was introduced in Qt 4.5.

See also textMargins().

void QLineEdit::setTextMargins(const QMargins &margins)

Sets the margins around the text inside the frame.

See also textMargins().

This function was introduced in Qt 4.6.

void QLineEdit::setValidator(const QValidator *v)

Sets the validator for values of line edit to v.

The line edit's returnPressed() and editingFinished() signals will only be emitted if v validates the line edit's content as Acceptable. The user may change the content to any Intermediate value during editing, but will be prevented from editing the text to a value that v validates as Invalid.

This allows you to constrain the text that shall finally be entered when editing is done, while leaving users with enough freedom to edit the text from one valid state to another.

If v == 0, setValidator() removes the current input validator. The initial setting is to have no input validator (i.e. any input is accepted up to maxLength()).

See also validator(), hasAcceptableInput(), QIntValidator, QDoubleValidator, and QRegExpValidator.

[override virtual] QSize QLineEdit::sizeHint() const

Reimplements an access function for property: QWidget::sizeHint.

Returns a recommended size for the widget.

The width returned, in pixels, is usually enough for about 15 to 20 characters.

QMargins QLineEdit::textMargins() const

Returns the widget's text margins.

This function was introduced in Qt 4.6.

See also setTextMargins().

const QValidator *QLineEdit::validator() const

Returns a pointer to the current input validator, or nullptr if no validator has been set.

See also setValidator().