Qt textedit и plaintextedit в чем разница

Qt textedit и plaintextedit в чем разница

На этом шаге рассмотрим класс QTextEdit многострочного текстового редактора.

Класс QTextEdit позволяет осуществлять просмотр и редактирование как простого текста, так и текста в формате HTML. Он унаследован от класса QAbstractScrollArea, что дает возможность автоматически отображать полосы прокрутки, если текст не может быть полностью отображен в отведенной для него области.

Если вам нужен редактор для обычного текста, то целесообразнее будет воспользоваться вместо класса QTextEdit классом QPlaintTextEdit. Класс QPlaintTextEdit не поддерживает RTF (Rich Text Format, формат обогащенного текста), в силу чего является более легковесным, простым и эффективным.

Класс QTextEdit содержит следующие методы:

Слоты класса QTextEdit:

Для работы с выделенным текстом служит класс QTextCursor, и объект этого класса содержится в классе QTextEdit. Класс QTextCursor предоставляет методы для создания участков выделения текста, получения содержимого выделенного текста и его удаление.

Указатель на объект класса QTextCursor можно получить вызовом метода QTextEdit::textCursor().

Виджеты класса QTextEdit также содержат в себе объект QTextDocument, указатель на который можно получить посредством метода QTextEdit::document(). Можно также присвоить другой документ при помощи метода QTextEdit::setDocument().

Класс QTextDocument предоставляет слот undo() (для отмены) или redo() (для повтора действий). При вызове слотов undo() и redo() посылаются сигналы undoAvailable(bool) и redoAvailable(bool), сообщающие об успешном (или безуспешном) проведении операции. Эти сигналы отправляются как из класса QTextDocument, так и из QTextEdit. В большинстве случаев удобнее будет использовать сигналы класса QTextEdit.

Большинство методов класса QTextEdit являются делегирующими для класса QTextDocument. Например, как уже было сказано ранее, класс QTextEdit способен отображать файлы с кодом на языке HTML, содержащие таблицы и растровые изображения. Для его размещения и показа можно воспользоваться методом setHtml(), в который передается строка, содержащая в себе текст в формате HTML, или воспользоваться слотом insertHtml(). Эти методы определены в обоих классах, и их вызов из объекта класса QTextEdit приведет к тому, что будет вызван аналогичный метод из объекта класса QTextDocument.

Для помещения обычного текста в область виджета можно воспользоваться методом setPlainText() или слотом insertPlainText(). При помощи слота append() осуществляется добавление текста, причем добавленный текст не вносится в список операций, действие которых можно вернуть с помощью слота undo(), что делает этот слот быстрым и не требующим дополнительных затрат памяти. Метод find() может быть использован для поиска и выделения заданной строки в тексте.

Слоты zoomIn() и zoomOut() предназначены для увеличения или уменьшения размера шрифта, и их действие не распространяется на растровые изображения.

Приведенный на рис. 1 пример отображает HTML-документ. Текст документа можно редактировать.

Рис.1. Пример отображения HTML-документа

В листинге приводится фрагмент текста из файла приложения, окно которого показано на рис. 1:

Файлы приложения можно взять здесь.

На следующем шаге рассмотрим запись содержимого объекта в файл.

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Qt Documentation

Contents

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

Public Types

Properties

Public Functions

Reimplemented Public Functions

Public Slots

Signals

Protected Functions

Reimplemented Protected Functions

Detailed Description

Introduction and Concepts

QTextEdit is an advanced WYSIWYG viewer/editor supporting rich text formatting using HTML-style tags, or Markdown format. It is optimized to handle large documents and to respond quickly to user input.

QTextEdit 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.

QTextEdit can display images, lists and tables. If the text is too large to view within the text edit’s viewport, scroll bars will appear. The text edit can load both plain text and rich text files. Rich text can be described using a subset of HTML 4 markup; refer to the Supported HTML Subset page for more information.

If you just need to display a small piece of rich text use QLabel.

The rich text support in Qt is designed to provide a fast, portable and efficient way to add reasonable online help facilities to applications, and to provide a basis for rich text editors. If you find the HTML support insufficient for your needs you may consider the use of Qt WebKit, which provides a full-featured web browser widget.

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

Using QTextEdit as a Display Widget

QTextEdit can display a large HTML subset, including tables and images.

The text can be set or replaced using setHtml() which deletes any existing text and replaces it with the text passed in the setHtml() call. If you call setHtml() with legacy HTML, and then call toHtml(), the text that is returned may have different markup, but will render the same. The entire text can be deleted with clear().

Text can also be set or replaced using setMarkdown(), and the same caveats apply: if you then call toMarkdown(), the text that is returned may be different, but the meaning is preserved as much as possible. Markdown with some embedded HTML can be parsed, with the same limitations that setHtml() has; but toMarkdown() only writes «pure» Markdown, without any embedded HTML.

Text itself can be inserted using the QTextCursor class or using the convenience functions insertHtml(), insertPlainText(), append() or paste(). QTextCursor is also able to insert complex objects like tables or lists into the document, and it deals with creating selections and applying changes to selected text.

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, or NoWrap if you don’t want any wrapping. Call setLineWrapMode() to set a fixed pixel width FixedPixelWidth, or character column (e.g. 80 column) FixedColumnWidth with the pixels or columns specified with setLineWrapColumnOrWidth(). 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 QTextEdit, as for example it is often useful in a log viewer, then you can use QTextDocument’s maximumBlockCount property for that.

Read-only Key Bindings

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

The text edit may be able to provide some meta-information. For example, the documentTitle() function will return the text from within HTML tags.

Note: Zooming into HTML documents only works if the font-size is not set to a fixed size.

Using QTextEdit as an Editor

All the information about using QTextEdit 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 QTextEdit just create one on a QTextCursor object and then make that cursor the visible cursor using setTextCursor(). 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().

When the cursor is moved and the underlying formatting attributes change, the currentCharFormatChanged() signal is emitted to reflect the new attributes at the new cursor position.

The textChanged() signal is emitted whenever the text changes (as a result of setText() or through the editor itself).

QTextEdit holds a QTextDocument object which can be retrieved using the document() method. You can also set your own document object using setDocument().

QTextDocument provides an 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.

Drag and Drop

QTextEdit also supports custom drag and drop behavior. By default, QTextEdit will insert plain text, HTML and rich text when the user drops data of these MIME types onto a document. Reimplement canInsertFromMimeData() and insertFromMimeData() to add support for additional MIME types.

For example, to allow the user to drag and drop an image onto a QTextEdit, you could the implement these functions in the following way:

We add support for image MIME types by returning true. For all other MIME types, we use the default implementation.

We unpack the image from the QVariant held by the MIME source and insert it into the document as a resource.

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 will select the character to the right, and Shift+Ctrl+Right will select the word to the right, etc.

Member Type Documentation

enum QTextEdit:: AutoFormattingFlag
flags QTextEdit:: AutoFormatting

enum QTextEdit:: LineWrapMode

Property Documentation

acceptRichText : bool

This property holds whether the text edit accepts rich text insertions by the user

When this propery is set to false text edit will accept only plain text input from the user. For example through clipboard or drag and drop.

This property’s default is true.

This property was introduced in Qt 4.1.

autoFormatting : AutoFormatting

This property holds the enabled set of auto formatting features

The value can be any combination of the values in the AutoFormattingFlag enum. The default is AutoNone. Choose AutoAll to enable all automatic formatting.

Currently, the only automatic formatting feature provided is AutoBulletList; future versions of Qt may offer more.

cursorWidth : int

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

This property was introduced in Qt 4.2.

document : QTextDocument *

This property holds the underlying document of the text editor.

Note: The editor does not take ownership of the document unless it is the document’s parent object. The parent object of the provided document remains the owner of the object. If the previously assigned document is a child of the editor then it will be deleted.

documentTitle : QString

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

By default, for a newly-created, empty document, this property contains an empty string.

html : QString

This property provides an HTML interface to the text of the text edit.

toHtml() returns the text of the text edit as html.

setHtml() changes the text of the text edit. Any previous text is removed and the undo/redo history is cleared. The input text is interpreted as rich text in html format. currentCharFormat() is also reset, unless textCursor() is already at the beginning of the document.

Note: It is the responsibility of the caller to make sure that the text is correctly decoded when a QString containing HTML is created and passed to setHtml().

By default, for a newly-created, empty document, this property contains text to describe an HTML 4.0 document with no body text.

lineWrapColumnOrWidth : int

This property holds the position (in pixels or columns depending on the wrap mode) where text will be wrapped

If the wrap mode is FixedPixelWidth, the value is the number of pixels from the left edge of the text edit at which text should be wrapped. If the wrap mode is FixedColumnWidth, the value is the column number (in character columns) from the left edge of the text edit at which text should be wrapped.

By default, this property contains a value of 0.

lineWrapMode : LineWrapMode

This property holds the line wrap mode

The default mode is WidgetWidth 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 use setWordWrapMode(). If you set a wrap mode of FixedPixelWidth or FixedColumnWidth you should also call setLineWrapColumnOrWidth() with the width you want.

markdown : QString

This property provides a Markdown interface to the text of the text edit.

toMarkdown() returns the text of the text edit as «pure» Markdown, without any embedded HTML formatting. Some features that QTextDocument supports (such as the use of specific colors and named fonts) cannot be expressed in «pure» Markdown, and they will be omitted.

setMarkdown() changes the text of the text edit. Any previous text is removed and the undo/redo history is cleared. The input text is interpreted as rich text in Markdown format.

Parsing of HTML included in the markdown string is handled in the same way as in setHtml; however, Markdown formatting inside HTML blocks is not supported.

Some features of the parser can be enabled or disabled via the features argument:

This property was introduced in Qt 5.14.

overwriteMode : bool

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

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

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

This property was introduced in Qt 4.1.

placeholderText : QString

This property holds the editor placeholder text

Setting this property makes the editor display a grayed-out placeholder text as long as the document() is empty.

By default, this property contains an empty string.

This property was introduced in Qt 5.2.

plainText : QString

This property gets and sets the text editor’s contents as plain text. Previous contents are removed and undo/redo history is reset when the property is set. currentCharFormat() is also reset, unless textCursor() is already at the beginning of the document.

If the text edit has another content type, it will not be replaced by plain text if you call toPlainText(). The only exception to this is the non-break space, nbsp;, that will be converted into standard space.

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

This property was introduced in Qt 4.3.

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.

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 the Tab key, as this breaks the focus chain. The default is false.

tabStopDistance : qreal

This property holds the tab stop distance in pixels

By default, this property contains a value of 80 pixels.

This property was introduced in Qt 5.10.

textInteractionFlags : Qt::TextInteractionFlags

Specifies how the widget should interact with user input.

The default value depends on whether the QTextEdit is read-only or editable, and whether it is a QTextBrowser or not.

This property was introduced in Qt 4.2.

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).

wordWrapMode : QTextOption::WrapMode

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

Member Function Documentation

QTextEdit:: QTextEdit (const QString &text, QWidget *parent = nullptr)

Constructs a QTextEdit with parent parent. The text edit will display the text text. The text is interpreted as html.

QTextEdit:: QTextEdit ( QWidget *parent = nullptr)

Constructs an empty QTextEdit with parent parent.

[slot] void QTextEdit:: append (const QString &text)

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

Note: The new paragraph appended will have the same character format and block format as the current paragraph, determined by the position of the cursor.

[slot] void QTextEdit:: clear ()

Deletes all the text in the text edit.

[slot] void QTextEdit:: copy ()

Copies any selected text to the clipboard.

[signal] void QTextEdit:: 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 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.

[signal] void QTextEdit:: currentCharFormatChanged (const QTextCharFormat &f)

This signal is emitted if the current character format has changed, for example caused by a change of the cursor position.

The new format is f.

[signal] void QTextEdit:: cursorPositionChanged ()

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

[slot] void QTextEdit:: cut ()

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

If there is no selected text nothing happens.

[slot] void QTextEdit:: insertHtml (const QString &text)

Convenience slot that inserts text which is assumed to be of html formatting at the current cursor position.

It is equivalent to:

Note: When using this function with a style sheet, the style sheet will only apply to the current block in the document. In order to apply a style sheet throughout a document, use QTextDocument::setDefaultStyleSheet() instead.

[slot] void QTextEdit:: insertPlainText (const QString &text)

Convenience slot that inserts text at the current cursor position.

It is equivalent to

[slot] void QTextEdit:: 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 QTextEdit can paste and how it is being pasted, reimplement the virtual canInsertFromMimeData() and insertFromMimeData() functions.

[slot] void QTextEdit:: 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.

This function was introduced in Qt 4.2.

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

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

[slot] void QTextEdit:: scrollToAnchor (const QString &name)

Scrolls the text edit so that the anchor with the given name is visible; does nothing if the name is empty, or is already visible, or isn’t found.

[slot] void QTextEdit:: selectAll ()

[signal] void QTextEdit:: selectionChanged ()

This signal is emitted whenever the selection changes.

[slot] void QTextEdit:: setAlignment ( Qt::Alignment a)

Sets the alignment of the current paragraph to a. Valid alignments are Qt::AlignLeft, Qt::AlignRight, Qt::AlignJustify and Qt::AlignCenter (which centers horizontally).

[slot] void QTextEdit:: setCurrentFont (const QFont &f)

Sets the font of the current format to f.

[slot] void QTextEdit:: setFontFamily (const QString &fontFamily)

Sets the font family of the current format to fontFamily.

[slot] void QTextEdit:: setFontItalic ( bool italic)

If italic is true, sets the current format to italic; otherwise sets the current format to non-italic.

[slot] void QTextEdit:: setFontPointSize ( qreal s)

Sets the point size of the current format to s.

Note that if s is zero or negative, the behavior of this function is not defined.

[slot] void QTextEdit:: setFontUnderline ( bool underline)

If underline is true, sets the current format to underline; otherwise sets the current format to non-underline.

[slot] void QTextEdit:: setFontWeight ( int weight)

Sets the font weight of the current format to the given weight, where the value used is in the range defined by the QFont::Weight enum.

[slot] void QTextEdit:: setPlainText (const QString &text)

Changes the text of the text edit to the string text. Any previous text is removed.

Note: Setter function for property plainText.

[slot] void QTextEdit:: setText (const QString &text)

Sets the text edit’s text. The text can be plain text or HTML and the text edit will try to guess the right format.

Use setHtml() or setPlainText() directly to avoid text edit’s guessing.

This function was introduced in Qt 4.2.

[slot] void QTextEdit:: setTextBackgroundColor (const QColor &c)

Sets the text background color of the current format to c.

This function was introduced in Qt 4.4.

[slot] void QTextEdit:: setTextColor (const QColor &c)

Sets the text color of the current format to c.

[signal] void QTextEdit:: textChanged ()

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

Note: Notifier signal for property html. Notifier signal for property markdown.

[slot] void QTextEdit:: 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.

This function was introduced in Qt 4.2.

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

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

[slot] void QTextEdit:: zoomIn ( int range = 1)

Zooms in on the text by making the base font size range points larger and recalculating all font sizes to be the new size. This does not change the size of any images.

[slot] void QTextEdit:: zoomOut ( int range = 1)

Zooms out on the text by making the base font size range points smaller and recalculating all font sizes to be the new size. This does not change the size of any images.

[virtual] QTextEdit::

Qt::Alignment QTextEdit:: alignment () const

Returns the alignment of the current paragraph.

QString QTextEdit:: anchorAt (const QPoint &pos) const

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

[virtual protected] bool QTextEdit:: canInsertFromMimeData (const QMimeData *source) const

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 and drop operation.

Reimplement this function to enable drag and drop support for additional MIME types.

bool QTextEdit:: canPaste () const

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

This function was introduced in Qt 4.2.

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

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

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.

[virtual protected] QMimeData *QTextEdit:: 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 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 *QTextEdit:: createStandardContextMenu ()

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

We recommend that you use the createStandardContextMenu(QPoint) version instead which will enable the actions that are sensitive to where the user clicked.

QMenu *QTextEdit:: createStandardContextMenu (const QPoint &position)

This function creates the standard context menu which is shown when the user clicks on the text edit with the right mouse button. It is called from the default contextMenuEvent() handler and it takes the position in document coordinates where the mouse click was. This can enable actions that are sensitive to the position where the user clicked. The popup menu’s ownership is transferred to the caller.

This function was introduced in Qt 4.4.

QTextCharFormat QTextEdit:: currentCharFormat () const

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

QFont QTextEdit:: currentFont () const

Returns the font of the current format.

QTextCursor QTextEdit:: cursorForPosition (const QPoint &pos) const

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

QRect QTextEdit:: cursorRect (const QTextCursor &cursor) const

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

QRect QTextEdit:: cursorRect () const

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

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

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

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

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

void QTextEdit:: ensureCursorVisible ()

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

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

Returns previously set extra selections.

This function was introduced in Qt 4.2.

bool QTextEdit:: find (const QString &exp, QTextDocument::FindFlags options = QTextDocument::FindFlags())

bool QTextEdit:: find (const QRegExp &exp, QTextDocument::FindFlags options = QTextDocument::FindFlags())

This is an overloaded function.

Finds the next occurrence, matching the regular expression, exp, using the given options. The QTextDocument::FindCaseSensitively option is ignored for this overload, use QRegExp::caseSensitivity instead.

This function was introduced in Qt 5.3.

bool QTextEdit:: find (const QRegularExpression &exp, QTextDocument::FindFlags options = QTextDocument::FindFlags())

This is an overloaded function.

Finds the next occurrence, matching the regular expression, exp, using the given options. The QTextDocument::FindCaseSensitively option is ignored for this overload, use QRegularExpression::CaseInsensitiveOption instead.

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