文本高亮

对于textedit里录入的部分单词我们可以实现高亮，实现高亮主要依赖于QSyntaxHighlighter。 我们先创建一个Qt Application类，类名MainWindow, 然后新增一个C++类，类名为MySyntaxHighlighter。

#ifndef MYSYNTAXHIGHLIGHTER_H
#define MYSYNTAXHIGHLIGHTER_H
#include <QSyntaxHighlighter>
#include <QTextDocument>
class MySyntaxHighlighter:public QSyntaxHighlighter
{
    Q_OBJECT
public:
    explicit MySyntaxHighlighter(QTextDocument* parent = 0);
    //重写实现高亮
protected:
    void highlightBlock(const QString& text);
};

#endif // MYSYNTAXHIGHLIGHTER_H

这个类声明了highlightBlock函数，这是一个虚函数继承自QSyntaxHighlighter。每次我们录入文字时，会自动调用这个函数。下面实现MySyntaxHighlighter类

#include "mysyntaxhighlighter.h"
#include <QFont>

MySyntaxHighlighter::MySyntaxHighlighter(QTextDocument* parent):QSyntaxHighlighter (parent)
{

}

void MySyntaxHighlighter::highlightBlock(const QString &text)
{
    QTextCharFormat myFormat;
    myFormat.setFont(QFont("微软雅黑"));
    myFormat.setFontWeight(QFont::Bold);
    myFormat.setForeground(Qt::green);
    //匹配char
    QString pattern = "\\bchar\\b";
    //创建正则表达式
    QRegExp express(pattern);
    //从索引0的位置开始匹配
    int index = text.indexOf(express);
    while (index>0) {
        int matchLen = express.matchedLength();
        //对匹配的字符串设置高亮
        setFormat(index, matchLen, myFormat);
        index = text.indexOf(express, index+matchLen);
    }
}

在highlightBlock函数中，我们实现了一个高亮的文字模式，当录入的字符串包含char时，char会被高亮。 我们在mainwindow.ui中添加一个textedit，然后在mainwindow的构造函数中添加我们刚才编写的高亮模块。

MainWindow::MainWindow(QWidget *parent) :
    QMainWindow(parent),
    ui(new Ui::MainWindow)
{
    ui->setupUi(this);
    m_ligher = new MySyntaxHighlighter(ui->textEdit->document());
}

程序运行后，在编辑器中输入hello char，会看到char高亮了

实现代码编辑器

Qt 的案例中有提供过文本高亮和显示行号的demo，我把它整理起来了。 我们先声明codeeditor类，以及行号显示的类

#ifndef CODEEDITOR_H
#define CODEEDITOR_H

#include <QPlainTextEdit>

QT_BEGIN_NAMESPACE
class QPaintEvent;
class QResizeEvent;
class QSize;
class QWidget;
QT_END_NAMESPACE

class LineNumberArea;

class CodeEditor : public QPlainTextEdit
{
    Q_OBJECT

public:
    CodeEditor(QWidget *parent = nullptr);

    void lineNumberAreaPaintEvent(QPaintEvent *event);
    int lineNumberAreaWidth();

protected:
    void resizeEvent(QResizeEvent *event) override;

private slots:
    void updateLineNumberAreaWidth(int newBlockCount);
    void highlightCurrentLine();
    void updateLineNumberArea(const QRect &rect, int dy);

private:
    QWidget *lineNumberArea;
};

class LineNumberArea : public QWidget
{
public:
    LineNumberArea(CodeEditor *editor) : QWidget(editor), codeEditor(editor)
    {}

    QSize sizeHint() const override
    {
        return QSize(codeEditor->lineNumberAreaWidth(), 0);
    }

protected:
    void paintEvent(QPaintEvent *event) override
    {
        codeEditor->lineNumberAreaPaintEvent(event);
    }

private:
    CodeEditor *codeEditor;
};

#endif

具体代码类的实现

#include "codeeditor.h"

#include <QPainter>
#include <QTextBlock>

CodeEditor::CodeEditor(QWidget *parent) : QPlainTextEdit(parent)
{
    lineNumberArea = new LineNumberArea(this);

    connect(this, &CodeEditor::blockCountChanged, this, &CodeEditor::updateLineNumberAreaWidth);
    connect(this, &CodeEditor::updateRequest, this, &CodeEditor::updateLineNumberArea);
    connect(this, &CodeEditor::cursorPositionChanged, this, &CodeEditor::highlightCurrentLine);

    updateLineNumberAreaWidth(0);
    highlightCurrentLine();
}

int CodeEditor::lineNumberAreaWidth()
{
    int digits = 1;
    int max = qMax(1, blockCount());
    while (max >= 10) {
        max /= 10;
        ++digits;
    }

    int space = 3 + fontMetrics().horizontalAdvance(QLatin1Char('9')) * digits;

    return space;
}

void CodeEditor::updateLineNumberAreaWidth(int /* newBlockCount */)
{
    setViewportMargins(lineNumberAreaWidth(), 0, 0, 0);
}

void CodeEditor::updateLineNumberArea(const QRect &rect, int dy)
{
    if (dy)
        lineNumberArea->scroll(0, dy);
    else
        lineNumberArea->update(0, rect.y(), lineNumberArea->width(), rect.height());

    if (rect.contains(viewport()->rect()))
        updateLineNumberAreaWidth(0);
}

void CodeEditor::resizeEvent(QResizeEvent *e)
{
    QPlainTextEdit::resizeEvent(e);

    QRect cr = contentsRect();
    lineNumberArea->setGeometry(QRect(cr.left(), cr.top(), lineNumberAreaWidth(), cr.height()));
}

void CodeEditor::highlightCurrentLine()
{
    QList<QTextEdit::ExtraSelection> extraSelections;

    if (!isReadOnly()) {
        QTextEdit::ExtraSelection selection;

        QColor lineColor = QColor(Qt::yellow).lighter(160);

        selection.format.setBackground(lineColor);
        selection.format.setProperty(QTextFormat::FullWidthSelection, true);
        selection.cursor = textCursor();
        selection.cursor.clearSelection();
        extraSelections.append(selection);
    }

    setExtraSelections(extraSelections);
}

void CodeEditor::lineNumberAreaPaintEvent(QPaintEvent *event)
{
    QPainter painter(lineNumberArea);
    painter.fillRect(event->rect(), Qt::lightGray);

    QTextBlock block = firstVisibleBlock();
    int blockNumber = block.blockNumber();
    int top = qRound(blockBoundingGeometry(block).translated(contentOffset()).top());
    int bottom = top + qRound(blockBoundingRect(block).height());

    while (block.isValid() && top <= event->rect().bottom()) {
        if (block.isVisible() && bottom >= event->rect().top()) {
            QString number = QString::number(blockNumber + 1);
            painter.setPen(Qt::black);
            painter.drawText(0, top, lineNumberArea->width(), fontMetrics().height(),
                             Qt::AlignHCenter, number);
        }

        block = block.next();
        top = bottom;
        bottom = top + qRound(blockBoundingRect(block).height());
        ++blockNumber;
    }
}

上面实现了代码编辑器的行号和当前行黄色高亮显示。 接下来实现高亮显示类

#ifndef HIGHLIGHTER_H
#define HIGHLIGHTER_H

#include <QSyntaxHighlighter>
#include <QTextCharFormat>
#include <QRegularExpression>

QT_BEGIN_NAMESPACE
class QTextDocument;
QT_END_NAMESPACE

//! [0]
class Highlighter : public QSyntaxHighlighter
{
    Q_OBJECT

public:
    Highlighter(QTextDocument *parent = 0);

protected:
    void highlightBlock(const QString &text) override;

private:
    struct HighlightingRule
    {
        QRegularExpression pattern;
        QTextCharFormat format;
    };
    QVector<HighlightingRule> highlightingRules;

    QRegularExpression commentStartExpression;
    QRegularExpression commentEndExpression;

    QTextCharFormat keywordFormat;
    QTextCharFormat classFormat;
    QTextCharFormat singleLineCommentFormat;
    QTextCharFormat multiLineCommentFormat;
    QTextCharFormat quotationFormat;
    QTextCharFormat functionFormat;
};
//! [0]

#endif // HIGHLIGHTER_H

具体实现细节如下，先定义高亮的正则规则，然后在highlightBlock函数里根据规则点亮不同的单词

#include "highlighter.h"

//! [0]
Highlighter::Highlighter(QTextDocument *parent)
    : QSyntaxHighlighter(parent)
{
    HighlightingRule rule;

    keywordFormat.setForeground(Qt::darkBlue);
    keywordFormat.setFontWeight(QFont::Bold);
    const QString keywordPatterns[] = {
        QStringLiteral("\\bchar\\b"), QStringLiteral("\\bclass\\b"), QStringLiteral("\\bconst\\b"),
        QStringLiteral("\\bdouble\\b"), QStringLiteral("\\benum\\b"), QStringLiteral("\\bexplicit\\b"),
        QStringLiteral("\\bfriend\\b"), QStringLiteral("\\binline\\b"), QStringLiteral("\\bint\\b"),
        QStringLiteral("\\blong\\b"), QStringLiteral("\\bnamespace\\b"), QStringLiteral("\\boperator\\b"),
        QStringLiteral("\\bprivate\\b"), QStringLiteral("\\bprotected\\b"), QStringLiteral("\\bpublic\\b"),
        QStringLiteral("\\bshort\\b"), QStringLiteral("\\bsignals\\b"), QStringLiteral("\\bsigned\\b"),
        QStringLiteral("\\bslots\\b"), QStringLiteral("\\bstatic\\b"), QStringLiteral("\\bstruct\\b"),
        QStringLiteral("\\btemplate\\b"), QStringLiteral("\\btypedef\\b"), QStringLiteral("\\btypename\\b"),
        QStringLiteral("\\bunion\\b"), QStringLiteral("\\bunsigned\\b"), QStringLiteral("\\bvirtual\\b"),
        QStringLiteral("\\bvoid\\b"), QStringLiteral("\\bvolatile\\b"), QStringLiteral("\\bbool\\b")
    };
    for (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(QStringLiteral("\\bQ[A-Za-z]+\\b"));
    rule.format = classFormat;
    highlightingRules.append(rule);
//! [2]

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

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

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

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

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

//! [7]
void Highlighter::highlightBlock(const QString &text)
{
    for (const HighlightingRule &rule : qAsConst(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]

接下来在MainWindow里添加editor

void MainWindow::setupEditor()
{
    QFont font;
    font.setFamily("Courier");
    font.setFixedPitch(true);
    font.setPointSize(10);

    editor = new CodeEditor();
    editor->setFont(font);

    highlighter = new Highlighter(editor->document());

    QFile file("mainwindow.h");
    if (file.open(QFile::ReadOnly | QFile::Text))
        editor->setPlainText(file.readAll());
}

运行程序后,输入部分代码显示如下 具体细节大家可以参考代码理解即可。

总结

源码链接https://gitee.com/secondtonone1/qt-learning-notes