QML TextEdit 語法高亮顯示

• QT手冊中關於TextEdit和QSyntaxHighlighter介紹如下：
  TextEdit QML Type
  QSyntaxHighlighter Class

• 語法高亮的實現關鍵描述如下圖：
  
  就是說TextEdit的textDocument屬性返回的是一個QQuickTextDocument類型的變量，而這個類型是可以用QSyntaxHighlighter實現語法高亮的（QSyntaxHighlighter的作用類型爲QTextDocument，我們可以通過QQuickTextDocument::textDocument() 函數得到）

• Qt語法高亮官方使用示例：
  Syntax Highlighter Example
  示例工程源碼地址
  我是直接用的官方示例的源碼，只是重寫了setDocument這個函數

• Highlighter.cpp

Highlighter::Highlighter(QQuickTextDocument  *parent)
    : QSyntaxHighlighter(parent)
{
    HighlightingRule rule;

    keywordFormat.setForeground(Qt::darkBlue);
    keywordFormat.setFontWeight(QFont::Bold);
    QStringList keywordPatterns;
    keywordPatterns << "\\bchar\\b" << "\\bclass\\b" << "\\bconst\\b"
                    << "\\bdouble\\b" << "\\benum\\b" << "\\bexplicit\\b"
                    << "\\bfriend\\b" << "\\binline\\b" << "\\bint\\b"
                    << "\\blong\\b" << "\\bnamespace\\b" << "\\boperator\\b"
                    << "\\bprivate\\b" << "\\bprotected\\b" << "\\bpublic\\b"
                    << "\\bshort\\b" << "\\bsignals\\b" << "\\bsigned\\b"
                    << "\\bslots\\b" << "\\bstatic\\b" << "\\bstruct\\b"
                    << "\\btemplate\\b" << "\\btypedef\\b" << "\\btypename\\b"
                    << "\\bunion\\b" << "\\bunsigned\\b" << "\\bvirtual\\b"
                    << "\\bvoid\\b" << "\\bvolatile\\b" << "\\bbool\\b"
                    << "\\bfunction\\b"  << "\\bend\\b";
    foreach (const QString &pattern, keywordPatterns) {
        rule.pattern = QRegularExpression(pattern);
        rule.format = keywordFormat;
        highlightingRules.append(rule);
//! [0] //! [1]
    }
//! [1]

//! [2]
    classFormat.setFontWeight(QFont::Bold);
    classFormat.setForeground(Qt::darkMagenta);
    rule.pattern = QRegularExpression("\\bQ[A-Za-z]+\\b");
    rule.format = classFormat;
    highlightingRules.append(rule);
//! [2]

//! [3]
    singleLineCommentFormat.setForeground(Qt::red);
    rule.pattern = QRegularExpression("//[^\n]*");
    rule.format = singleLineCommentFormat;
    highlightingRules.append(rule);

    multiLineCommentFormat.setForeground(Qt::red);
//! [3]

//! [4]
    quotationFormat.setForeground(Qt::darkGreen);
    rule.pattern = QRegularExpression("\".*\"");
    rule.format = quotationFormat;
    highlightingRules.append(rule);

    rule.pattern = QRegularExpression("\'.*\'");
    rule.format = quotationFormat;
    highlightingRules.append(rule);
    //! [4]

//! [5]
    functionFormat.setFontItalic(true);
    functionFormat.setForeground(Qt::blue);
    rule.pattern = QRegularExpression("\\b[A-Za-z0-9_]+(?=\\()");
    rule.format = functionFormat;
    highlightingRules.append(rule);
//! [5]

//! [6]
    commentStartExpression = QRegularExpression("/\\*");
    commentEndExpression = QRegularExpression("\\*/");
}
//! [6]

//! [7]
void Highlighter::highlightBlock(const QString &text)
{
    qDebug("%s", __FUNCTION__);
    foreach (const HighlightingRule &rule, highlightingRules) {
        QRegularExpressionMatchIterator matchIterator = rule.pattern.globalMatch(text);
        while (matchIterator.hasNext()) {
            QRegularExpressionMatch match = matchIterator.next();
            setFormat(match.capturedStart(), match.capturedLength(), rule.format);
        }
    }
//! [7] //! [8]
    setCurrentBlockState(0);
//! [8]

//! [9]
    int startIndex = 0;
    if (previousBlockState() != 1)
        startIndex = text.indexOf(commentStartExpression);

//! [9] //! [10]
    while (startIndex >= 0) {
//! [10] //! [11]
        QRegularExpressionMatch match = commentEndExpression.match(text, startIndex);
        int endIndex = match.capturedStart();
        int commentLength = 0;
        if (endIndex == -1) {
            setCurrentBlockState(1);
            commentLength = text.length() - startIndex;
        } else {
            commentLength = endIndex - startIndex
                            + match.capturedLength();
        }
        setFormat(startIndex, commentLength, multiLineCommentFormat);
        startIndex = text.indexOf(commentStartExpression, startIndex + commentLength);
    }
}
//! [11]

//上面都是示例源碼，我只寫了下面這個函數
void Highlighter::setDocument(QQuickTextDocument *pDoc)
{
    QSyntaxHighlighter::setDocument(pDoc->textDocument());
}

• 在main.cpp 中註冊Highlighter類：

    qmlRegisterType<Highlighter>("qml.highlighter", 1, 0, "Highlighter");

• 在qml文件中創建Highlighter， 在TextEdit的Component.onCompleted函數中完成setDocument動作：

import qml.highlighter 1.0
Rectangle{
        TextEdit{
            Layout.fillHeight: true
            Layout.fillWidth: true
            id:editor
            cursorVisible: true
            selectByMouse: true
            Component.onCompleted: {
                hilighter.setDocument(editor.textDocument);
            }
        }

        Highlighter{
            id:hilighter
        }
}