QTextObjectInterface 类

The QTextObjectInterface class allows drawing of custom text objects in QTextDocument 。更多...

头：	#include <QTextObjectInterface>
qmake:	QT += gui
Since:	Qt 4.5

所有成员列表，包括继承成员

公共函数

virtual	~QTextObjectInterface ()
virtual void	drawObject (QPainter * painter , const QRectF & rect , QTextDocument * doc , int posInDocument , const QTextFormat & format ) = 0
virtual QSizeF	intrinsicSize (QTextDocument * doc , int posInDocument , const QTextFormat & format ) = 0

详细描述

The QTextObjectInterface class allows drawing of custom text objects in QTextDocument 。

A text object describes the structure of one or more elements in a text document; for instance, images imported from HTML are implemented using text objects. A text object knows how to lay out and draw its elements when a document is being rendered.

Qt allows custom text objects to be inserted into a document by registering a custom 对象类型 with QTextCharFormat 。 QTextObjectInterface must also be implemented for this type and be registered 采用 QAbstractTextDocumentLayout of the document. When the object type is encountered while rendering a QTextDocument ， intrinsicSize () 和 drawObject () functions of the interface are called.

The following list explains the required steps of inserting a custom text object into a document:

Choose an objectType 。 objectType is an integer with a value greater or equal to QTextFormat::UserObject .
创建 QTextCharFormat object and set the object type to the chosen type using the setObjectType() function.
Implement the QTextObjectInterface 类。
调用 QAbstractTextDocumentLayout::registerHandler () with an instance of your QTextObjectInterface subclass to register your object type.
Insert QChar::ObjectReplacementCharacter with the aforementioned QTextCharFormat of the chosen object type into the document. As mentioned, the functions of QTextObjectInterface intrinsicSize() and drawObject() will then be called with the QTextFormat as parameter whenever the replacement character is encountered.

A class implementing a text object needs to inherit both QObject and QTextObjectInterface . QObject must be the first class inherited. For instance:

class SvgTextObject : public QObject, public QTextObjectInterface
{
    Q_OBJECT
    Q_INTERFACES(QTextObjectInterface)

The data of a text object is usually stored in the QTextCharFormat 使用 QTextCharFormat::setProperty (), and then retrieved with QTextCharFormat::property ().

警告： 拷贝和粘贴操作忽略自定义文本对象。

另请参阅 文本对象范例 , QTextCharFormat ，和 QTextLayout .

成员函数文档编制

`[虚拟]` QTextObjectInterface:: ~QTextObjectInterface ()

销毁此 QTextObjectInterface .

`[pure virtual]` void QTextObjectInterface:: drawObject ( QPainter * painter , const QRectF & rect , QTextDocument * doc , int posInDocument , const QTextFormat & format )

绘制此文本对象使用指定 painter .

The size of the rectangle, rect , to draw in is the size previously calculated by intrinsicSize (). The rectangles position is relative to the painter .

You also get the document ( doc ) and the position ( posInDocument ) of the format in that document.

另请参阅 intrinsicSize ().

`[pure virtual]` QSizeF QTextObjectInterface:: intrinsicSize ( QTextDocument * doc , int posInDocument , const QTextFormat & format )

The intrinsicSize() function returns the size of the text object represented by format in the given document ( doc ) at the given position ( posInDocument ).

The size calculated will be used for subsequent calls to drawObject () for this format .

另请参阅 drawObject ().

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