The QAbstractTextDocumentLayout class is an abstract base class used to implement custom layouts for QTextDocuments. 更多...
继承 QObject .
Inherited by QPlainTextDocumentLayout .
The QAbstractTextDocumentLayout class is an abstract base class used to implement custom layouts for QTextDocuments.
The standard layout provided by Qt can handle simple word processing including inline images, lists and tables.
Some applications, e.g., a word processor or a DTP application might need more features than the ones provided by Qt's layout engine, in which case you can subclass QAbstractTextDocumentLayout to provide custom layout behavior for your text documents.
An instance of the QAbstractTextDocumentLayout subclass can be installed on a QTextDocument object with the setDocumentLayout() 函数。
You can insert custom objects into a QTextDocument ; see the QTextObjectInterface class description for details.
Creates a new text document layout for the given document .
Returns the reference of the anchor the given position , or an empty string if no anchor exists at that point.
This method is abstract and should be reimplemented in any sub-class.
Returns the bounding rectangle of block .
Returns the text document that this layout is operating on.
This method is abstract and should be reimplemented in any sub-class.
This function is called whenever the contents of the document change. A change occurs when text is inserted, removed, or a combination of these two. The change is specified by position , charsRemoved ，和 charsAdded corresponding to the starting character position of the change, the number of characters removed from the document, and the number of characters added.
For example, when inserting the text "Hello" into an empty document, charsRemoved would be 0 and charsAdded would be 5 (the length of the string).
Replacing text is a combination of removing and inserting. For example, if the text "Hello" gets replaced by "Hi", charsRemoved would be 5 and charsAdded would be 2.
For subclasses of QAbstractTextDocumentLayout , this is the central function where a large portion of the work to lay out and position document contents is done.
For example, in a subclass that only arranges blocks of text, an implementation of this function would have to do the following:
另请参阅 QTextLayout .
This method is abstract and should be reimplemented in any sub-class.
Returns the total size of the document's layout.
This information can be used by display widgets to update their scroll bars correctly.
另请参阅 documentSizeChanged () and QTextDocument.pageSize .
This method is abstract and should be reimplemented in any sub-class.
Draws the layout with the given painter using the given context .
This function is called to draw the inline object, object ，采用给定 painter within the rectangle 指定通过 rect using the specified text format .
posInDocument specifies the position of the object within the document.
The default implementation calls drawObject() on the object handlers. This function is called only within Qt. Subclasses can reimplement this function to customize the drawing of inline 对象。
另请参阅 draw ().
Returns the character format that is applicable at the given position .
This method is abstract and should be reimplemented in any sub-class.
Returns the bounding rectangle of frame .
Returns a handler for objects of the given objectType .
This method is abstract and should be reimplemented in any sub-class.
Returns the cursor postion for the given point 采用 specified accuracy . Returns -1 if no valid cursor position was found.
This method is abstract and should be reimplemented in any sub-class.
Returns the number of pages contained in the layout.
另请参阅 pageCountChanged ().
Returns the paint device used to render the document's layout.
另请参阅 setPaintDevice ().
Lays out the inline object item using the given text format .
posInDocument specifies the position of the object within the document.
The default implementation does nothing. This function is called only within Qt. Subclasses can reimplement this function to customize the position of inline objects.
另请参阅 drawInlineObject ().
Registers the given component as a handler for items of the given objectType .
注意： registerHandler() has to be called once for each object type. This means that there is only one handler for multiple replacement characters of the same object type.
Sets the size of the inline object item corresponding to the text format .
posInDocument specifies the position of the object within the document.
The default implementation resizes the item to the size returned by the object handler's intrinsicSize() function. This function is called only within Qt. Subclasses can reimplement this function to customize the resizing of inline objects.
Sets the paint device used for rendering the document's layout 到给定 device .
另请参阅 paintDevice ().
This is the default overload of this signal.
This signal is emitted when the size of the document layout changes to newSize .
Subclasses of QAbstractTextDocumentLayout should emit this signal when the document's entire layout size changes. This signal is useful for widgets that display text documents since it enables them to update their scroll bars correctly.
另请参阅 documentSize ().
This is the default overload of this signal.
This signal is emitted when the number of pages in the layout changes; newPages is the updated page count.
Subclasses of QAbstractTextDocumentLayout should emit this signal when the number of pages in the layout has changed. Changes to the page count are caused by changes to the layout or the document content itself.
另请参阅 pageCount ().
This is the default overload of this signal.
This signal is emitted when the rectangle rect has been updated.
Subclasses of QAbstractTextDocumentLayout should emit this signal when the layout of the contents change in order to repaint.
This is the default overload of this signal.
此信号被发射当指定 block has been updated.
Subclasses of QAbstractTextDocumentLayout should emit this signal when the layout of block has changed in order to repaint.
该函数在 Qt 4.4 引入。
