QTextObjectInterface 类

详细说明

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 object type with QTextCharFormat. A QTextObjectInterface must also be implemented for this type and be registered with the QAbstractTextDocumentLayout of the document. When the object type is encountered while rendering a QTextDocument, the intrinsicSize() and drawObject() functions of the interface are called.

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

• 选择一个 objectType。The objectType 是一个大于或等于 QTextFormat::UserObject 的整数。
• 创建一个 QTextCharFormat 对象，并使用 setObjectType() 函数将对象类型设置为所选类型。
• 实现 QTextObjectInterface 类。
• 使用您的 QTextObjectInterface 子类实例调用 QAbstractTextDocumentLayout::registerHandler() 以注册您的对象类型。
• 将上述QChar::ObjectReplacementCharacter插入到文档中，并与所选对象类型的QTextCharFormat一起。正如前面所述，每当遇到替换字符时，将使用QTextFormat作为参数调用QTextObjectInterface的intrinsicSize()和drawObject()函数。

实现文本对象的类需要继承QObject和QTextObjectInterface。其中，QObject必须是继承的第一个类。例如

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

文本对象的数据通常使用QTextCharFormat和QTextCharFormat::setProperty()存储，然后通过QTextCharFormat::property()检索。