Contents

• Public Types
• Properties
• Public Functions
• Public Slots
• Signals
• Protected Functions
• Reimplemented Protected Functions
• Detailed Description
• Introduction and Concepts
• Using QPlainTextEdit as a Display Widget
• Using QPlainTextEdit as an Editor
• Differences to QTextEdit

Detailed Description

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

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 asQTextEdit, 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. 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 aQPlainTextEdit isQt::IBeamCursor by default. It can be changed through theviewport()'s cursor property.

Using QPlainTextEdit as a Display Widget

The text is set or replaced usingsetPlainText() which deletes the existing text and replaces it with the text passed tosetPlainText().

Text can be inserted using theQTextCursor class or using the convenience functionsinsertPlainText(),appendPlainText() orpaste().

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

Thefind() 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 aQPlainTextEdit, as it is for example useful in a log viewer, then you can use themaximumBlockCount property. The combination ofsetMaximumBlockCount() andappendPlainText() turnsQPlainTextEdit into an efficient viewer for log text. The scrolling can be reduced with thecenterOnScroll() 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 withappendHtml(). WhileQPlainTextEdit 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

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

Using QPlainTextEdit as an Editor

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

Selection of text is handled by theQTextCursor 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 thetextCursor() method. If you want to set a selection inQPlainTextEdit just create one on aQTextCursor object and then make that cursor the visible cursor usingsetCursor(). The selection can be copied to the clipboard withcopy(), or cut to the clipboard withcut(). The entire text can be selected usingselectAll().

QPlainTextEdit holds aQTextDocument object which can be retrieved using thedocument() method. You can also set your own document object usingsetDocument().QTextDocument emits atextChanged() 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 likeQTextEdit,QPlainTextEdit works together withQSyntaxHighlighter.

Editing Key Bindings

The list of key bindings which are implemented for editing:

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, andShift+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 behindQTextEdit andQTextDocument. Its performance benefits overQTextEdit stem mostly from using a different and simplified text layout calledQPlainTextDocumentLayout on the text document (seeQTextDocument::setDocumentLayout()). The plain text document layout does not support tables nor embedded frames, andreplaces 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 (seesetMaximumBlockCount()).

Member Type Documentation

enum QPlainTextEdit::LineWrapMode

Property Documentation

backgroundVisible :bool

This property holds whether the palette background is visible outside the document area.

If set to true, the plain text edit paints the palette background on the viewport area not covered by the text document. Otherwise, if set to false, it won't. The feature makes it possible for the user to visually distinguish between the area of the document, painted with the base color of the palette, and the empty area not covered by any document.

The default is false.

Access functions:

blockCount : constint

This property holds the number of text blocks in the document.

By default, in an empty document, this property contains a value of 1.

Access functions:

centerOnScroll :bool

This property holds whether the cursor should be centered on screen.

If set to true, the plain text edit scrolls the document vertically to make the cursor visible at the center of the viewport. This also allows the text edit to scroll below the end of the document. Otherwise, if set to false, the plain text edit scrolls the smallest amount possible to ensure the cursor is visible. The same algorithm is applied to any new line appended throughappendPlainText().

The default is false.

Access functions:

See alsocenterCursor() andensureCursorVisible().

cursorWidth :int

This property specifies the width of the cursor in pixels. The default value is 1.

Access functions:

documentTitle :QString

This property holds the title of the document parsed from the text.

By default, this property contains an empty string.

Access functions:

lineWrapMode :LineWrapMode

This property holds the line wrap mode.

The default mode isWidgetWidth which causes words to be wrapped at the right edge of the text edit. Wrapping occurs at whitespace, keeping whole words intact. If you want wrapping to occur within words usesetWordWrapMode().

Access functions:

maximumBlockCount :int

This property holds the limit for blocks in the document.

Specifies the maximum number of blocks the document may have. If there are more blocks in the document that specified with this property blocks are removed from the beginning of the document.

A negative or zero value specifies that the document may contain an unlimited amount of blocks.

The default value is 0.

Note that setting this property will apply the limit immediately to the document contents. Setting this property also disables the undo redo history.

Access functions:

overwriteMode :bool

This property holds whether text entered by the user will overwrite existing text.

As with many text editors, the plain text editor widget can be configured to insert or overwrite existing text with new text entered by the user.

If this property is true, existing text is overwritten, character-for-character by new text; otherwise, text is inserted at the cursor position, displacing existing text.

By default, this property is false (new text does not overwrite existing text).

Access functions:

plainText :QString

This property gets and sets the plain text editor's contents. The previous contents are removed and undo/redo history is reset when this property is set.

By default, for an editor with no contents, this property contains an empty string.

Access functions:

Notifier signal:

readOnly :bool

This property holds whether the text edit is read-only.

In a read-only text edit the user can only navigate through the text and select text; modifying the text is not possible.

This property's default is false.

Access functions:

tabChangesFocus :bool

This property holds whether Tab changes focus or is accepted as input.

In some occasions text edits should not allow the user to input tabulators or change indentation using theTab key, as this breaks the focus chain. The default is false.

Access functions:

tabStopWidth :int

This property holds the tab stop width in pixels.

By default, this property contains a value of 80.

Access functions:

textInteractionFlags :Qt::TextInteractionFlags

Specifies how the label should interact with user input if it displays text.

If the flags contain eitherQt::LinksAccessibleByKeyboard orQt::TextSelectableByKeyboard then the focus policy is also automatically set toQt::ClickFocus.

The default value depends on whether theQPlainTextEdit is read-only or editable.

Access functions:

undoRedoEnabled :bool

This property holds whether undo and redo are enabled.

Users are only able to undo or redo actions if this property is true, and if there is an action that can be undone (or redone).

By default, this property is true.

Access functions:

wordWrapMode :QTextOption::WrapMode

This property holds the mode QPlainTextEdit will use when wrapping text by words.

By default, this property is set toQTextOption::WrapAtWordBoundaryOrAnywhere.

Access functions:

See alsoQTextOption::WrapMode.

Member Function Documentation

QPlainTextEdit::QPlainTextEdit(QWidget * parent = 0)

Constructs an emptyQPlainTextEdit with parentparent.

QPlainTextEdit::QPlainTextEdit(constQString & text,QWidget * parent = 0)

Constructs aQPlainTextEdit with parentparent. The text edit will display the plain texttext.

[virtual]QPlainTextEdit::~QPlainTextEdit()

Destructor.

QString QPlainTextEdit::anchorAt(constQPoint & pos) const

Returns the reference of the anchor at positionpos, or an empty string if no anchor exists at that point.

This function was introduced in Qt 4.7.

[slot]void QPlainTextEdit::appendHtml(constQString & html)

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

appendPlainText()

[slot]void QPlainTextEdit::appendPlainText(constQString & text)

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

See alsoappendHtml().

[protected]QRectF QPlainTextEdit::blockBoundingGeometry(constQTextBlock & block) const

Returns the bounding rectangle of the textblock in content coordinates. Translate the rectangle with thecontentOffset() to get visual coordinates on the viewport.

See alsofirstVisibleBlock() andblockBoundingRect().

[protected]QRectF QPlainTextEdit::blockBoundingRect(constQTextBlock & block) const

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

See alsoblockBoundingGeometry().

[signal]void QPlainTextEdit::blockCountChanged(int newBlockCount)

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

[virtual protected]bool QPlainTextEdit::canInsertFromMimeData(constQMimeData * source) const

This function returns true if the contents of the MIME data object, specified bysource, 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() const

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

[slot]void QPlainTextEdit::centerCursor()

Scrolls the document in order to center the cursor vertically.

See alsoensureCursorVisible() andcenterOnScroll.

[virtual protected]void QPlainTextEdit::changeEvent(QEvent * e)

Reimplemented fromQWidget::changeEvent().

[slot]void QPlainTextEdit::clear()

Deletes all the text in the text edit.

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

See alsocut() andsetPlainText().

[protected]QPointF QPlainTextEdit::contentOffset() const

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 alsofirstVisibleBlock(),horizontalScrollBar(), andverticalScrollBar().

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

Reimplemented fromQWidget::contextMenuEvent().

Shows the standard context menu created withcreateStandardContextMenu().

If you do not want the text edit to have a context menu, you can set itscontextMenuPolicy toQt::NoContextMenu. If you want to customize the context menu, reimplement this function. If you want to extend the standard context menu, reimplement this function, callcreateStandardContextMenu() and extend the menu returned.

Information about the event is passed in theevent object.

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

[slot]void QPlainTextEdit::copy()

Copies any selected text to the clipboard.

See alsocopyAvailable().

[signal]void QPlainTextEdit::copyAvailable(bool yes)

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

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

Ifyes is true thencopy() can be used to copy the selection to the clipboard. Ifyes is false thencopy() does nothing.

See alsoselectionChanged().

[virtual protected]QMimeData * QPlainTextEdit::createMimeDataFromSelection() const

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 newQMimeData 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 returnedQMimeData object is passed to the caller. The selection can be retrieved by using thetextCursor() function.

QMenu * QPlainTextEdit::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 defaultcontextMenuEvent() handler. The popup menu's ownership is transferred to the caller.

QTextCharFormat QPlainTextEdit::currentCharFormat() const

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

See alsosetCurrentCharFormat().

QTextCursor QPlainTextEdit::cursorForPosition(constQPoint & pos) const

returns aQTextCursor at positionpos (in viewport coordinates).

[signal]void QPlainTextEdit::cursorPositionChanged()

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

QRect QPlainTextEdit::cursorRect(constQTextCursor & cursor) const

returns a rectangle (in viewport coordinates) that includes thecursor.

QRect QPlainTextEdit::cursorRect() const

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

[slot]void QPlainTextEdit::cut()

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

If there is no selected text nothing happens.

See alsocopy() andpaste().

QTextDocument * QPlainTextEdit::document() const

Returns a pointer to the underlying document.

See alsosetDocument().

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

Reimplemented fromQWidget::dragEnterEvent().

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

Reimplemented fromQWidget::dragLeaveEvent().

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

Reimplemented fromQWidget::dragMoveEvent().

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

Reimplemented fromQWidget::dropEvent().

void QPlainTextEdit::ensureCursorVisible()

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

See alsocenterCursor() andcenterOnScroll.

QList<QTextEdit::ExtraSelection> QPlainTextEdit::extraSelections() const

Returns previously set extra selections.

See alsosetExtraSelections().

bool QPlainTextEdit::find(constQString & exp,QTextDocument::FindFlags options = 0)

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

[protected]QTextBlock QPlainTextEdit::firstVisibleBlock() const

Returns the first visible block.

See alsoblockBoundingRect().

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

Reimplemented fromQWidget::focusInEvent().

[virtual protected]bool QPlainTextEdit::focusNextPrevChild(bool next)

Reimplemented fromQWidget::focusNextPrevChild().

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

Reimplemented fromQWidget::focusOutEvent().

[protected]QAbstractTextDocumentLayout::PaintContext QPlainTextEdit::getPaintContext() const

Returns the paint context for theviewport(), useful only when reimplementingpaintEvent().

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

Reimplemented fromQWidget::inputMethodEvent().

[virtual protected]QVariant QPlainTextEdit::inputMethodQuery(Qt::InputMethodQuery property) const

Reimplemented fromQWidget::inputMethodQuery().

[virtual protected]void QPlainTextEdit::insertFromMimeData(constQMimeData * source)

This function inserts the contents of the MIME data object, specified bysource, 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.

[slot]void QPlainTextEdit::insertPlainText(constQString & text)

Convenience slot that insertstext at the current cursor position.

It is equivalent to

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

[virtual protected]void QPlainTextEdit::keyPressEvent(QKeyEvent * e)

Reimplemented fromQWidget::keyPressEvent().

[virtual protected]void QPlainTextEdit::keyReleaseEvent(QKeyEvent * e)

Reimplemented fromQWidget::keyReleaseEvent().

[virtual]QVariant QPlainTextEdit::loadResource(int type, constQUrl & name)

Loads the resource specified by the giventype andname.

This function is an extension ofQTextDocument::loadResource().

See alsoQTextDocument::loadResource().

void QPlainTextEdit::mergeCurrentCharFormat(constQTextCharFormat & modifier)

Merges the properties specified inmodifier into the current character format by callingQTextCursor::mergeCharFormat on the editor's cursor. If the editor has a selection then the properties ofmodifier are directly applied to the selection.

See alsoQTextCursor::mergeCharFormat().

[signal]void QPlainTextEdit::modificationChanged(bool changed)

This signal is emitted whenever the content of the document changes in a way that affects the modification state. Ifchanged 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.

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

Reimplemented fromQWidget::mouseDoubleClickEvent().

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

Reimplemented fromQWidget::mouseMoveEvent().

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

Reimplemented fromQWidget::mousePressEvent().

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

Reimplemented fromQWidget::mouseReleaseEvent().

void QPlainTextEdit::moveCursor(QTextCursor::MoveOperation operation,QTextCursor::MoveMode mode = QTextCursor::MoveAnchor)

Moves the cursor by performing the givenoperation.

Ifmode isQTextCursor::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 alsoQTextCursor::movePosition().

[virtual protected]void QPlainTextEdit::paintEvent(QPaintEvent * e)

Reimplemented fromQWidget::paintEvent().

[slot]void QPlainTextEdit::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 whatQPlainTextEdit can paste and how it is being pasted, reimplement the virtualcanInsertFromMimeData() andinsertFromMimeData() functions.

See alsocut() andcopy().

void QPlainTextEdit::print(QPrinter * printer) const

Convenience function to print the text edit's document to the givenprinter. This is equivalent to calling the print method on the document directly except that this function also supportsQPrinter::Selection as print range.

See alsoQTextDocument::print().

[slot]void QPlainTextEdit::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 alsoundo().

[signal]void QPlainTextEdit::redoAvailable(bool available)

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

[virtual protected]void QPlainTextEdit::resizeEvent(QResizeEvent * e)

Reimplemented fromQWidget::resizeEvent().

[virtual protected]void QPlainTextEdit::scrollContentsBy(int dx,int dy)

Reimplemented fromQAbstractScrollArea::scrollContentsBy().

[slot]void QPlainTextEdit::selectAll()

Selects all text.

See alsocopy(),cut(), andtextCursor().

[signal]void QPlainTextEdit::selectionChanged()

This signal is emitted whenever the selection changes.

See alsocopyAvailable().

void QPlainTextEdit::setCurrentCharFormat(constQTextCharFormat & format)

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

See alsocurrentCharFormat().

void QPlainTextEdit::setDocument(QTextDocument * document)

Makesdocument the new document of the text editor.

The parentQObject 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 inheritsQPlainTextDocumentLayout (seeQTextDocument::setDocumentLayout()).

See alsodocument().

void QPlainTextEdit::setExtraSelections(constQList<QTextEdit::ExtraSelection> & selections)

This function allows temporarily marking certain regions in the document with a given color, specified asselections. 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 alsoQTextEdit::ExtraSelection andextraSelections().

void QPlainTextEdit::setTextCursor(constQTextCursor & cursor)

Sets the visiblecursor.

See alsotextCursor().

[virtual protected]void QPlainTextEdit::showEvent(QShowEvent *)

Reimplemented fromQWidget::showEvent().

QTextCursor QPlainTextEdit::textCursor() const

Returns a copy of theQTextCursor that represents the currently visible cursor. Note that changes on the returned cursor do not affectQPlainTextEdit's cursor; usesetTextCursor() to update the visible cursor.

See alsosetTextCursor().

[slot]void QPlainTextEdit::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 alsoredo().

[signal]void QPlainTextEdit::undoAvailable(bool available)

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

[signal]void QPlainTextEdit::updateRequest(constQRect & rect,int dy)

This signal is emitted when the text document needs an update of the specifiedrect. 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.

[virtual protected]void QPlainTextEdit::wheelEvent(QWheelEvent * e)

Reimplemented fromQWidget::wheelEvent().