精简版的textEditor

#ifndef CODEEDITOR_H

#define CODEEDITOR_H

#include <QtWidgets>

#include <QPlainTextEdit>

#include <QObject>

class QPaintEvent;

class QResizeEvent;

class QSize;

class QWidget;

class LineNumberArea;

class CodeEditor : public QPlainTextEdit

{

    Q_OBJECT

public:

    CodeEditor(QWidget *parent = 0);

    void drawLineNumbers(QPaintEvent *event);

    int lineNumberAreaWidth();

private slots:

    void highlightCurrentLine();

    void updateLineNumberArea(const QRect &, int);

private:

    QWidget *lineNumberArea;

};

class LineNumberArea : public QWidget

{

public:

    LineNumberArea(CodeEditor *editor) : QWidget(editor)

    {

        codeEditor = editor;

    }

protected:

    void paintEvent(QPaintEvent *event)

    {

        codeEditor->drawLineNumbers(event);

    }

private:

    CodeEditor *codeEditor;

};

#endif

//.cpp

#include "codeeditor.h"

CodeEditor::CodeEditor(QWidget *parent) : QPlainTextEdit(parent)

{

    lineNumberArea = new LineNumberArea(this);

    QRect cr = contentsRect();

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

    lineNumberArea->show();

    setWordWrapMode(QTextOption::NoWrap);

    connect(this, SIGNAL(updateRequest(QRect,int)), this, SLOT(updateLineNumberArea(QRect,int)));

    connect(this, SIGNAL(cursorPositionChanged()), this, SLOT(highlightCurrentLine()));

    setViewportMargins(lineNumberAreaWidth(), 0, 0, 0);

    highlightCurrentLine();

}

int CodeEditor::lineNumberAreaWidth()

{

    return 40;

}

void CodeEditor::updateLineNumberArea(const QRect &rect, int)

{

    lineNumberArea->update(0, rect.y(), lineNumberArea->width(), rect.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::drawLineNumbers(QPaintEvent *event)

{

    QPainter painter(lineNumberArea);

    painter.fillRect(event->rect(), Qt::lightGray);

    QTextBlock block = firstVisibleBlock();

    int blockNumber = block.blockNumber();

    int top = (int) blockBoundingGeometry(block).translated(contentOffset()).top();

    int bottom = top + (int) blockBoundingRect(block).height();

    while (block.isValid() && top <= event->rect().bottom())

    {

        if (block.isVisible() && bottom >= event->rect().top())

        {

            QString number = QString::number(blockNumber + 1).rightJustified(4,'0');

            painter.setPen(Qt::black);

            painter.drawText(0, top, lineNumberArea->width()-5, fontMetrics().height(),Qt::AlignRight, number);

        }

        block = block.next();

        top = bottom;

        bottom = top + (int) blockBoundingRect(block).height();

        ++blockNumber;

    }

    painter.setPen(Qt::green);

    painter.drawLine(lineNumberArea->width()-1,0,lineNumberArea->width()-1,lineNumberArea->height());

}

//main.cpp

#include <QtWidgets>

#include "codeeditor.h"

int main(int argv, char **args)

{

    QApplication app(argv, args);

    CodeEditor editor;

    editor.setWindowTitle(QObject::tr("Code Editor Example"));

    editor.show();

    return app.exec();

}