|  | Home · All Classes · Modules

# QPlainTextEdit Class Reference
[QtGui module]

The QPlainTextEdit class provides a widget that is used to edit and display plain text. More...

Inherits QAbstractScrollArea.

### Types

- enum LineWrapMode { NoWrap, WidgetWidth }

### Methods

- __init__ (self, QWidget parent = None)
- __init__ (self, QString text, QWidget parent = None)
- appendHtml (self, QString html)
- appendPlainText (self, QString text)
- bool backgroundVisible (self)
- QRectF blockBoundingGeometry (self, QTextBlock block)
- QRectF blockBoundingRect (self, QTextBlock block)
- int blockCount (self)
- bool canInsertFromMimeData (self, QMimeData source)
- bool canPaste (self)
- centerCursor (self)
- bool centerOnScroll (self)
- changeEvent (self, QEvent e)
- clear (self)
- QPointF contentOffset (self)
- contextMenuEvent (self, QContextMenuEvent e)
- copy (self)
- QMimeData createMimeDataFromSelection (self)
- QMenu createStandardContextMenu (self)
- QTextCharFormat currentCharFormat (self)
- QTextCursor cursorForPosition (self, QPoint pos)
- QRect cursorRect (self, QTextCursor cursor)
- QRect cursorRect (self)
- int cursorWidth (self)
- cut (self)
- QTextDocument document (self)
- QString documentTitle (self)
- dragEnterEvent (self, QDragEnterEvent e)
- dragLeaveEvent (self, QDragLeaveEvent e)
- dragMoveEvent (self, QDragMoveEvent e)
- dropEvent (self, QDropEvent e)
- ensureCursorVisible (self)
- bool event (self, QEvent e)
- QTextEdit.ExtraSelection-list extraSelections (self)
- bool find (self, QString exp, QTextDocument.FindFlags options = 0)
- QTextBlock firstVisibleBlock (self)
- focusInEvent (self, QFocusEvent e)
- bool focusNextPrevChild (self, bool next)
- focusOutEvent (self, QFocusEvent e)
- QAbstractTextDocumentLayout.PaintContext getPaintContext (self)
- inputMethodEvent (self, QInputMethodEvent)
- QVariant inputMethodQuery (self, Qt.InputMethodQuery property)
- insertFromMimeData (self, QMimeData source)
- insertPlainText (self, QString text)
- bool isReadOnly (self)
- bool isUndoRedoEnabled (self)
- keyPressEvent (self, QKeyEvent e)
- keyReleaseEvent (self, QKeyEvent e)
- LineWrapMode lineWrapMode (self)
- QVariant loadResource (self, int type, QUrl name)
- int maximumBlockCount (self)
- mergeCurrentCharFormat (self, QTextCharFormat modifier)
- mouseDoubleClickEvent (self, QMouseEvent e)
- mouseMoveEvent (self, QMouseEvent e)
- mousePressEvent (self, QMouseEvent e)
- mouseReleaseEvent (self, QMouseEvent e)
- moveCursor (self, QTextCursor.MoveOperation operation, QTextCursor.MoveMode mode = QTextCursor.MoveAnchor)
- bool overwriteMode (self)
- paintEvent (self, QPaintEvent e)
- paste (self)
- print (self, QPrinter printer)
- redo (self)
- resizeEvent (self, QResizeEvent e)
- scrollContentsBy (self, int dx, int dy)
- selectAll (self)
- setBackgroundVisible (self, bool visible)
- setCenterOnScroll (self, bool enabled)
- setCurrentCharFormat (self, QTextCharFormat format)
- setCursorWidth (self, int width)
- setDocument (self, QTextDocument document)
- setDocumentTitle (self, QString title)
- setExtraSelections (self, QTextEdit.ExtraSelection-list selections)
- setLineWrapMode (self, LineWrapMode mode)
- setMaximumBlockCount (self, int maximum)
- setOverwriteMode (self, bool overwrite)
- setPlainText (self, QString text)
- setReadOnly (self, bool ro)
- setTabChangesFocus (self, bool b)
- setTabStopWidth (self, int width)
- setTextCursor (self, QTextCursor cursor)
- setTextInteractionFlags (self, Qt.TextInteractionFlags flags)
- setUndoRedoEnabled (self, bool enable)
- setWordWrapMode (self, QTextOption.WrapMode policy)
- showEvent (self, QShowEvent)
- bool tabChangesFocus (self)
- int tabStopWidth (self)
- QTextCursor textCursor (self)
- Qt.TextInteractionFlags textInteractionFlags (self)
- timerEvent (self, QTimerEvent e)
- QString toPlainText (self)
- undo (self)
- wheelEvent (self, QWheelEvent e)
- QTextOption.WrapMode wordWrapMode (self)

### Qt Signals

- void blockCountChanged (int)
- void copyAvailable (bool)
- void cursorPositionChanged ()
- void modificationChanged (bool)
- void redoAvailable (bool)
- void selectionChanged ()
- void textChanged ()
- void undoAvailable (bool)
- void updateRequest (const QRect&,int)

## Detailed Description

The QPlainTextEdit class provides a widget that is used to edit and display plain text.

- Introduction and Concepts
- Using QPlainTextEdit as a Display Widget

- Read-only Key Bindings

- Using QPlainTextEdit as an Editor

- Syntax Highlighting
- Editing Key Bindings

- Differences to QTextEdit

### Introduction and Concepts

QPlainTextEdit is an advanced viewer/editor supporting plain text. It is optimized to handle large documents and to respond quickly to user input.

QPlainText uses very much the same technology and concepts as QTextEdit, but is optimized for plain text handling.

QPlainTextEdit works on paragraphs and characters. A paragraph is a formatted string which is word-wrapped to fit into the width of the widget. By default when reading plain text, one newline signifies a paragraph. A document consists of zero or more paragraphs. The words in the paragraph are aligned in accordance with the paragraph's alignment. Paragraphs are separated by hard line breaks. Each character within a paragraph has its own attributes, for example, font and color.

The shape of the mouse cursor on a QPlainTextEdit is Qt.IBeamCursor by default. It can be changed through the viewport()'s cursor property.

### Using QPlainTextEdit as a Display Widget

The text is set or replaced using setPlainText() which deletes any existing text and replaces it with the text passed in the setPlainText() call.

Text itself can be inserted using the QTextCursor class or using the convenience functins insertPlainText(), appendPlainText() or paste().

By default the text edit wraps words at whitespace to fit within the text edit widget. The setLineWrapMode() function is used to specify the kind of line wrap you want, WidgetWidth or NoWrap if you don't want any wrapping. If you use word wrap to the widget's width WidgetWidth, you can specify whether to break on whitespace or anywhere with setWordWrapMode().

The find() function can be used to find and select a given string within the text.

If you want to limit the total number of paragraphs in a QPlainTextEdit, as it is for example useful in a log viewer, then you can use the maximumBlockCount property. The combination of setMaximumBlockCount() and appendPlainText() turns QPlainTextEdit into an efficient viewer for log text. The scrolling can be reduced with the centerOnScroll() property, making the log viewer even faster. Text can be formatted in a limited way, either using a syntax highlighter (see below), or by appending html-formatted text with appendHtml(). While QPlainTextEdit does not support complex rich text rendering with tables and floats, it does support limited paragraph-based formatting that you may need in a log viewer.

#### Read-only Key Bindings

When QPlainTextEdit is used read-only the key bindings are limited to navigation, and text may only be selected with the mouse:

Keypresses | Action
--- | ---
Qt.UpArrow | Moves one line up.
Qt.DownArrow | Moves one line down.
Qt.LeftArrow | Moves one character to the left.
Qt.RightArrow | Moves one character to the right.
PageUp | Moves one (viewport) page up.
PageDown | Moves one (viewport) page down.
Home | Moves to the beginning of the text.
End | Moves to the end of the text.
Alt+Wheel | Scrolls the page horizontally (the Wheel is the mouse wheel).
Ctrl+Wheel | Zooms the text.
Ctrl+A | Selects all text.

### Using QPlainTextEdit as an Editor

All the information about using QPlainTextEdit as a display widget also applies here.

Selection of text is handled by the QTextCursor class, which provides functionality for creating selections, retrieving the text contents or deleting selections. You can retrieve the object that corresponds with the user-visible cursor using the textCursor() method. If you want to set a selection in QPlainTextEdit just create one on a QTextCursor object and then make that cursor the visible cursor using setCursor(). The selection can be copied to the clipboard with copy(), or cut to the clipboard with cut(). The entire text can be selected using selectAll().

QPlainTextEdit holds a QTextDocument object which can be retrieved using the document() method. You can also set your own document object using setDocument(). QTextDocument emits a textChanged() signal if the text changes and it also provides a isModified() function which will return true if the text has been modified since it was either loaded or since the last call to setModified with false as argument. In addition it provides methods for undo and redo.

#### Syntax Highlighting

Just like QTextEdit, QPlainTextEdit works together with QSyntaxHighlighter.

#### Editing Key Bindings

The list of key bindings which are implemented for editing:

Keypresses | Action
--- | ---
Backspace | Deletes the character to the left of the cursor.
Delete | Deletes the character to the right of the cursor.
Ctrl+C | Copy the selected text to the clipboard.
Ctrl+Insert | Copy the selected text to the clipboard.
Ctrl+K | Deletes to the end of the line.
Ctrl+V | Pastes the clipboard text into text edit.
Shift+Insert | Pastes the clipboard text into text 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 operation.
LeftArrow | Moves the cursor one character to the left.
Ctrl+LeftArrow | Moves the cursor one word to the left.
RightArrow | Moves the cursor one character to the right.
Ctrl+RightArrow | Moves the cursor one word to the right.
UpArrow | Moves the cursor one line up.
Ctrl+UpArrow | Moves the cursor one word up.
DownArrow | Moves the cursor one line down.
Ctrl+Down Arrow | Moves the cursor one word down.
PageUp | Moves the cursor one page up.
PageDown | Moves the cursor one page down.
Home | Moves the cursor to the beginning of the line.
Ctrl+Home | Moves the cursor to the beginning of the text.
End | Moves the cursor to the end of the line.
Ctrl+End | Moves the cursor to the end of the text.
Alt+Wheel | Scrolls the page horizontally (the Wheel is the mouse wheel).
Ctrl+Wheel | Zooms the text.

To select (mark) text hold down the Shift key whilst pressing one of the movement keystrokes, for example, Shift+Right Arrow will select the character to the right, and Shift+Ctrl+Right Arrow will select the word to the right, etc.

### Differences to QTextEdit

QPlainTextEdit is a thin class, implemented by using most of the technology that is behind QTextEdit and QTextDocument. Its performance benefits over QTextEdit stem mostly from using a different and simplified text layout called QPlainTextDocumentLayout on the text document (see QTextDocument.setDocumentLayout()). The plain text document layout does not support tables nor embedded frames, and replaces a pixel-exact height calculation with a line-by-line respectively paragraph-by-paragraph scrolling approach. This makes it possible to handle significantly larger documents, and still resize the editor with line wrap enabled in real time. It also makes for a fast log viewer (see setMaximumBlockCount()).

See also QTextDocument, QTextCursor, Application Example, Syntax Highlighter Example, and Rich Text Processing.

## Type Documentation

### QPlainTextEdit.LineWrapMode

Constant | Value
--- | ---
`QPlainTextEdit.NoWrap` | `0`
`QPlainTextEdit.WidgetWidth` | `1`

## Method Documentation

### QPlainTextEdit.__init__ (self, QWidget parent = None)

The parent argument, if not None, causes self to be owned by Qt instead of PyQt.

Constructs an empty QPlainTextEdit with parent parent.

### QPlainTextEdit.__init__ (self, QString text, QWidget parent = None)

The parent argument, if not None, causes self to be owned by Qt instead of PyQt.

Constructs a QPlainTextEdit with parent parent. The text edit will display the plain text text.

### QPlainTextEdit.appendHtml (self, QString html)

This method is also a Qt slot with the C++ signature `void appendHtml(const QString&)`.

Appends a new paragraph with html to the end of the text edit.

appendPlainText()

### QPlainTextEdit.appendPlainText (self, QString text)

This method is also a Qt slot with the C++ signature `void appendPlainText(const QString&)`.

Appends a new paragraph with text to the end of the text edit.

See also appendHtml().

### bool QPlainTextEdit.backgroundVisible (self)

### QRectF QPlainTextEdit.blockBoundingGeometry (self, QTextBlock block)

Returns the bounding rectangle of the text block in content coordinates. Translate the rectangle with the contentOffset() to get visual coordinates on the viewport.

See also firstVisibleBlock() and blockBoundingRect().

### QRectF QPlainTextEdit.blockBoundingRect (self, QTextBlock block)

Returns the bounding rectangle of the text block in the block's own coordinates.

See also blockBoundingGeometry().

### int QPlainTextEdit.blockCount (self)

### bool QPlainTextEdit.canInsertFromMimeData (self, QMimeData source)

This function returns true if the contents of the MIME data object, specified by source, can be decoded and inserted into the document. It is called for example when during a drag operation the mouse enters this widget and it is necessary to determine whether it is possible to accept the drag.

### bool QPlainTextEdit.canPaste (self)

Returns whether text can be pasted from the clipboard into the textedit.

### QPlainTextEdit.centerCursor (self)

This method is also a Qt slot with the C++ signature `void centerCursor()`.

Scrolls the document in order to center the cursor vertically.

See also ensureCursorVisible() and centerOnScroll.

### bool QPlainTextEdit.centerOnScroll (self)

### QPlainTextEdit.changeEvent (self, QEvent e)

### QPlainTextEdit.clear (self)

This method is also a Qt slot with the C++ signature `void clear()`.

Deletes all the text in the text edit.

Note that the undo/redo history is cleared by this function.

See also cut() and setPlainText().

### QPointF QPlainTextEdit.contentOffset (self)

Returns the content's origin in viewport coordinates.

The origin of the content of a plain text edit is always the top left corner of the first visible text block. The content offset is different from (0,0) when the text has been scrolled horizontally, or when the first visible block has been scrolled partially off the screen, i.e. the visible text does not start with the first line of the first visible block, or when the first visible block is the very first block and the editor displays a margin.

See also firstVisibleBlock(), horizontalScrollBar(), and verticalScrollBar().

### QPlainTextEdit.contextMenuEvent (self, QContextMenuEvent e)

Shows the standard context menu created with createStandardContextMenu().

If you do not want the text 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.

Information about the event is passed in the event object.

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

Reimplemented from QWidget.

### QPlainTextEdit.copy (self)

This method is also a Qt slot with the C++ signature `void copy()`.

Copies any selected text to the clipboard.

See also copyAvailable().

### QMimeData QPlainTextEdit.createMimeDataFromSelection (self)

This function returns a new MIME data object to represent the contents of the text edit's current selection. It is called when the selection needs to be encapsulated into a new QMimeData object; for example, when a drag and drop operation is started, or when data is copied to the clipboard.

If you reimplement this function, note that the ownership of the returned QMimeData object is passed to the caller. The selection can be retrieved by using the textCursor() function.

### QMenu QPlainTextEdit.createStandardContextMenu (self)

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.

### QTextCharFormat QPlainTextEdit.currentCharFormat (self)

Returns the char format that is used when inserting new text.

See also setCurrentCharFormat().

### QTextCursor QPlainTextEdit.cursorForPosition (self, QPoint pos)

returns a QTextCursor at position pos (in viewport coordinates).

### QRect QPlainTextEdit.cursorRect (self, QTextCursor cursor)

returns a rectangle (in viewport coordinates) that includes the cursor.

### QRect QPlainTextEdit.cursorRect (self)

This is an overloaded member function, provided for convenience.

returns a rectangle (in viewport coordinates) that includes the cursor of the text edit.

### int QPlainTextEdit.cursorWidth (self)

### QPlainTextEdit.cut (self)

This method is also a Qt slot with the C++ signature `void cut()`.

Copies the selected text to the clipboard and deletes it from the text edit.

If there is no selected text nothing happens.

See also copy() and paste().

### QTextDocument QPlainTextEdit.document (self)

Returns a pointer to the underlying document.

See also setDocument().

### QString QPlainTextEdit.documentTitle (self)

### QPlainTextEdit.dragEnterEvent (self, QDragEnterEvent e)

### QPlainTextEdit.dragLeaveEvent (self, QDragLeaveEvent e)

### QPlainTextEdit.dragMoveEvent (self, QDragMoveEvent e)

### QPlainTextEdit.dropEvent (self, QDropEvent e)

### QPlainTextEdit.ensureCursorVisible (self)

Ensures that the cursor is visible by scrolling the text edit if necessary.

See also centerCursor() and centerOnScroll.

### bool QPlainTextEdit.event (self, QEvent e)

### QTextEdit.ExtraSelection-list QPlainTextEdit.extraSelections (self)

Returns previously set extra selections.

See also setExtraSelections().

### bool QPlainTextEdit.find (self, QString exp, QTextDocument.FindFlags options = 0)

Finds the next occurrence of the string, exp, using the given options. Returns true if exp was found and changes the cursor to select the match; otherwise returns false.

### QTextBlock QPlainTextEdit.firstVisibleBlock (self)

Returns the first visible block.

See also blockBoundingRect().

### QPlainTextEdit.focusInEvent (self, QFocusEvent e)

### bool QPlainTextEdit.focusNextPrevChild (self, bool next)

### QPlainTextEdit.focusOutEvent (self, QFocusEvent e)

### QAbstractTextDocumentLayout.PaintContext QPlainTextEdit.getPaintContext (self)

Returns the paint context for the viewport(), useful only when reimplementing paintEvent().

### QPlainTextEdit.inputMethodEvent (self, QInputMethodEvent)

### QVariant QPlainTextEdit.inputMethodQuery (self, Qt.InputMethodQuery property)

### QPlainTextEdit.insertFromMimeData (self, QMimeData source)

This function inserts the contents of the MIME data object, specified by source, into the text edit at the current cursor position. It is called whenever text is inserted as the result of a clipboard paste operation, or when the text edit accepts data from a drag and drop operation.

### QPlainTextEdit.insertPlainText (self, QString text)

This method is also a Qt slot with the C++ signature `void insertPlainText(const QString&)`.

Convenience slot that inserts text at the current cursor position.

It is equivalent to

         edit->textCursor().insertText(text);

### bool QPlainTextEdit.isReadOnly (self)

### bool QPlainTextEdit.isUndoRedoEnabled (self)

### QPlainTextEdit.keyPressEvent (self, QKeyEvent e)

### QPlainTextEdit.keyReleaseEvent (self, QKeyEvent e)

### LineWrapMode QPlainTextEdit.lineWrapMode (self)

### QVariant QPlainTextEdit.loadResource (self, int type, QUrl name)

Loads the resource specified by the given type and name.

This function is an extension of QTextDocument.loadResource().

See also QTextDocument.loadResource().

### int QPlainTextEdit.maximumBlockCount (self)

### QPlainTextEdit.mergeCurrentCharFormat (self, QTextCharFormat modifier)

Merges the properties specified in modifier into the current character format by calling QTextCursor.mergeCharFormat on the editor's cursor. If the editor has a selection then the properties of modifier are directly applied to the selection.

See also QTextCursor.mergeCharFormat().

### QPlainTextEdit.mouseDoubleClickEvent (self, QMouseEvent e)

### QPlainTextEdit.mouseMoveEvent (self, QMouseEvent e)

### QPlainTextEdit.mousePressEvent (self, QMouseEvent e)

### QPlainTextEdit.mouseReleaseEvent (self, QMouseEvent e)

### QPlainTextEdit.moveCursor (self, QTextCursor.MoveOperation operation, QTextCursor.MoveMode mode = QTextCursor.MoveAnchor)

Moves the cursor by performing the given operation.

If mode is QTextCursor.KeepAnchor, the cursor selects the text it moves over. This is the same effect that the user achieves when they hold down the Shift key and move the cursor with the cursor keys.

See also QTextCursor.movePosition().

### bool QPlainTextEdit.overwriteMode (self)

### QPlainTextEdit.paintEvent (self, QPaintEvent e)

### QPlainTextEdit.paste (self)

This method is also a Qt slot with the C++ signature `void paste()`.

Pastes the text from the clipboard into the text edit at the current cursor position.

If there is no text in the clipboard nothing happens.

To change the behavior of this function, i.e. to modify what QPlainTextEdit can paste and how it is being pasted, reimplement the virtual canInsertFromMimeData() and insertFromMimeData() functions.

See also cut() and copy().

### QPlainTextEdit.print (self, QPrinter printer)

Convenience function to print the text edit's document to the given printer. This is equivalent to calling the print method on the document directly except that this function also supports QPrinter.Selection as print range.

See also QTextDocument.print().

### QPlainTextEdit.redo (self)

This method is also a Qt slot with the C++ signature `void redo()`.

Redoes the last operation.

If there is no operation to redo, i.e. there is no redo step in the undo/redo history, nothing happens.

See also undo().

### QPlainTextEdit.resizeEvent (self, QResizeEvent e)

### QPlainTextEdit.scrollContentsBy (self, int dx, int dy)

### QPlainTextEdit.selectAll (self)

This method is also a Qt slot with the C++ signature `void selectAll()`.

Selects all text.

See also copy(), cut(), and textCursor().

### QPlainTextEdit.setBackgroundVisible (self, bool visible)

### QPlainTextEdit.setCenterOnScroll (self, bool enabled)

### QPlainTextEdit.setCurrentCharFormat (self, QTextCharFormat format)

Sets the char format that is be used when inserting new text to format by calling QTextCursor.setCharFormat() on the editor's cursor. If the editor has a selection then the char format is directly applied to the selection.

See also currentCharFormat().

### QPlainTextEdit.setCursorWidth (self, int width)

### QPlainTextEdit.setDocument (self, QTextDocument document)

Makes document the new document of the text editor.

The parent QObject of the provided document remains the owner of the object. If the current document is a child of the text editor, then it is deleted.

The document must have a document layout that inherits QPlainTextDocumentLayout (see QTextDocument.setDocumentLayout()).

See also document().

### QPlainTextEdit.setDocumentTitle (self, QString title)

### QPlainTextEdit.setExtraSelections (self, QTextEdit.ExtraSelection-list selections)

This function allows temporarily marking certain regions in the document with a given color, specified as selections. This can be useful for example in a programming editor to mark a whole line of text with a given background color to indicate the existence of a breakpoint.

See also QTextEdit.ExtraSelection and extraSelections().

### QPlainTextEdit.setLineWrapMode (self, LineWrapMode mode)

### QPlainTextEdit.setMaximumBlockCount (self, int maximum)

### QPlainTextEdit.setOverwriteMode (self, bool overwrite)

### QPlainTextEdit.setPlainText (self, QString text)

This method is also a Qt slot with the C++ signature `void setPlainText(const QString&)`.

### QPlainTextEdit.setReadOnly (self, bool ro)

### QPlainTextEdit.setTabChangesFocus (self, bool b)

### QPlainTextEdit.setTabStopWidth (self, int width)

### QPlainTextEdit.setTextCursor (self, QTextCursor cursor)

Sets the visible cursor.

See also textCursor().

### QPlainTextEdit.setTextInteractionFlags (self, Qt.TextInteractionFlags flags)

### QPlainTextEdit.setUndoRedoEnabled (self, bool enable)

### QPlainTextEdit.setWordWrapMode (self, QTextOption.WrapMode policy)

### QPlainTextEdit.showEvent (self, QShowEvent)

### bool QPlainTextEdit.tabChangesFocus (self)

### int QPlainTextEdit.tabStopWidth (self)

### QTextCursor QPlainTextEdit.textCursor (self)

Returns a copy of the QTextCursor that represents the currently visible cursor. Note that changes on the returned cursor do not affect QPlainTextEdit's cursor; use setTextCursor() to update the visible cursor.

See also setTextCursor().

### Qt.TextInteractionFlags QPlainTextEdit.textInteractionFlags (self)

### QPlainTextEdit.timerEvent (self, QTimerEvent e)

### QString QPlainTextEdit.toPlainText (self)

### QPlainTextEdit.undo (self)

This method is also a Qt slot with the C++ signature `void undo()`.

Undoes the last operation.

If there is no operation to undo, i.e. there is no undo step in the undo/redo history, nothing happens.

See also redo().

### QPlainTextEdit.wheelEvent (self, QWheelEvent e)

### QTextOption.WrapMode QPlainTextEdit.wordWrapMode (self)

## Qt Signal Documentation

### void blockCountChanged (int)

This signal is emitted whenever the block count changes. The new block count is passed in newBlockCount.

### void copyAvailable (bool)

This signal is emitted when text is selected or de-selected in the text edit.

When text is selected this signal will be emitted with yes set to true. If no text has been selected or if the selected text is de-selected this signal is emitted with yes set to false.

If yes is true then copy() can be used to copy the selection to the clipboard. If yes is false then copy() does nothing.

See also selectionChanged().

### void cursorPositionChanged ()

This signal is emitted whenever the position of the cursor changed.

### void modificationChanged (bool)

This signal is emitted whenever the content of the document changes in a way that affects the modification state. If changed is true, the document has been modified; otherwise it is false.

For example, calling setModified(false) on a document and then inserting text causes the signal to get emitted. If you undo that operation, causing the document to return to its original unmodified state, the signal will get emitted again.

### void redoAvailable (bool)

This signal is emitted whenever redo operations become available (available is true) or unavailable (available is false).

### void selectionChanged ()

This signal is emitted whenever the selection changes.

See also copyAvailable().

### void textChanged ()

This signal is emitted whenever the document's content changes; for example, when text is inserted or deleted, or when formatting is applied.

### void undoAvailable (bool)

This signal is emitted whenever undo operations become available (available is true) or unavailable (available is false).

### void updateRequest (const QRect&,int)

This signal is emitted when the text document needs an update of the specified rect. If the text is scrolled, rect will cover the entire viewport area. If the text is scrolled vertically, dy carries the amount of pixels the viewport was scrolled.

The purpose of the signal is to support extra widgets in plain text edit subclasses that e.g. show line numbers, breakpoints, or other extra information.