QTextEdit将多个字符作为一个整体，不可单独修改

考虑一个问题，QTextEdit如何实现类似微信和QQ聊天输入框中的“@xxx”效果，其内容作为一个整体，以突出颜色显示，并且不可以单独编辑修改，只能整体删除修改。

突出颜色显示有很多方式可以实现，例如

通过setTextColor接口，此接口可以设置当前字体颜色为指定颜色

//保存当前颜色
QColor _color = this->textColor();
//设置为红色
this->setTextColor(Qt::red);
//添加文字
this->append("hello world");
//恢复颜色
this->setTextColor(_color);

通过html格式实现

this->append("<font color=\"#FF0000\">红色字体</font> ");

通过QTextCharFormat实现

auto cursor = this->textCursor();
//备份格式auto backFormat = cursor.charFormat();//设置字体auto _font_size = this->font().pointSize();//构建格式QTextCharFormat _format;//设置文本颜色_format.setForeground(Qt::red);cursor.insertText(QString(QChar::ObjectReplacementCharacter),_format);//恢复默认格式this->setCurrentCharFormat(backFormat);

颜色搞定了，如何将指定的字符串设为整体呢？
通过面向百度编程和查阅文档（主要是面向百度编程，哈哈）找到一种方法。
众所周知，QTextEdit中的内容是有QTextDocument类实现渲染的，而QTextDocument的布局方式是由QAbstractTextDocumentLayout实现的，可以通过QAbstractTextDocumentLayout *QTextDocument::documentLayout()接口获取。而在QAbstractTextDocumentLayout类中提供了
void registerHandler(int objectType, QObject *component)接口可以注册自定义的Handler实现自定义绘制。因此可以通过此方式实现将多个文本作为整体。

先看效果
在这里插入图片描述
继承QTextObjectInterface实现intrinsicSize和drawObject

enum TextFormatRole
{//字体大小Format_FontSize = QTextFormat::UserProperty + 1,//文本Format_Text
};
class TextEditHander : public QObject,QTextObjectInterface
{Q_OBJECTQ_INTERFACES(QTextObjectInterface)
public:TextEditHander(QObject* parent = nullptr);~TextEditHander();//计算绘制区域QSizeF intrinsicSize(QTextDocument *doc, int posInDocument,const QTextFormat &format) override;void drawObject(QPainter *painter, const QRectF &rect, QTextDocument *doc,int posInDocument, const QTextFormat &format) override;};

TextEditHander::TextEditHander(QObject *parent):QObject(parent)
{}TextEditHander::~TextEditHander()
{}//计算绘制区域
QSizeF TextEditHander::intrinsicSize(QTextDocument *doc, int posInDocument,const QTextFormat &format)
{//获取字体大小int font_size = format.property(Format_FontSize).toInt();QString text = format.property(TextFormatRole::Format_Text).toString();auto _font = doc->defaultFont();_font.setPointSize(font_size);QFontMetrics _metrics(_font);int textWidth = _metrics.horizontalAdvance(text);return QSizeF(textWidth,_metrics.height());
}//绘制
void TextEditHander::drawObject(QPainter *painter, const QRectF &rect,QTextDocument *doc, int posInDocument, const QTextFormat &format)
{Q_UNUSED(doc);Q_UNUSED(posInDocument);QString text = format.property(Format_Text).toString();int font_size = format.property(Format_FontSize).toInt();//调整rect
//    QRectF _drawRect = rect.adjusted(0,1,0,-1);QRectF _drawRect = rect;//绘制painter->save();//绘制背景painter->fillRect(_drawRect,format.background());//绘制文字auto _font = doc->defaultFont();_font.setPointSize(font_size);painter->setFont(_font);painter->setPen(format.foreground().color());painter->drawText(_drawRect,Qt::AlignBaseline,text);painter->restore();
}

继承QTextEdit

class TextEdit : public QTextEdit
{Q_OBJECT
public:explicit TextEdit(QWidget *parent = nullptr);virtual ~TextEdit() = default;
protected slots://插入标签void slot_addText();
};

TextEdit::TextEdit(QWidget *parent): QTextEdit{parent}
{//注册handlerauto handler = new TextEditHander(this);this->document()->documentLayout()->registerHandler(QTextFormat::UserObject+1,handler);QFont _font = this->font();_font.setPointSize(12);this->setFont(_font);//创建右键菜单QAction *act = new QAction("插入标签",this);connect(act,&QAction::triggered,this,&TextEdit::slot_addText);this->addAction(act);this->setContextMenuPolicy(Qt::ActionsContextMenu);
}void TextEdit::slot_addText()
{auto cursor = this->textCursor();//备份格式auto backFormat = cursor.charFormat();//设置字体auto _font_size = this->font().pointSize();//构建格式QTextCharFormat _format;//设置格式使用自定义的Hander渲染，这步很重要_format.setObjectType(QTextFormat::UserObject + 1);//设置需要绘制的文本_format.setProperty(TextFormatRole::Format_Text,"${123}");//设置字体大小_format.setProperty(TextFormatRole::Format_FontSize,_font_size);//设置前景色_format.setForeground(Qt::black);//设置背景色_format.setBackground(Qt::lightGray);cursor.insertText(QString(QChar::ObjectReplacementCharacter),_format);//恢复默认格式this->setCurrentCharFormat(backFormat);//添加一个空格this->textCursor().insertText(" ");}