- Qt 5.5
- Qt Widgets
- Code Editor Example
- codeeditor.cpp Example File
- Qt 5.5.1 Reference Documentation

# codeeditor.cpp Example File

widgets/codeeditor/codeeditor.cpp

    /****************************************************************************
    **
    ** Copyright (C) 2015 The Qt Company Ltd.
    ** Contact: http://www.qt.io/licensing/
    **
    ** This file is part of the examples of the Qt Toolkit.
    **
    ** $QT_BEGIN_LICENSE:BSD$
    ** You may use this file under the terms of the BSD license as follows:
    **
    ** "Redistribution and use in source and binary forms, with or without
    ** modification, are permitted provided that the following conditions are
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    **   * Redistributions of source code must retain the above copyright
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    **     notice, this list of conditions and the following disclaimer in
    **     the documentation and/or other materials provided with the
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    **     contributors may be used to endorse or promote products derived
    **     from this software without specific prior written permission.
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    #include <QtWidgets>

    #include "codeeditor.h"

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

        connect(this, SIGNAL(blockCountChanged(int)), this, SLOT(updateLineNumberAreaWidth(int)));
        connect(this, SIGNAL(updateRequest(QRect,int)), this, SLOT(updateLineNumberArea(QRect,int)));
        connect(this, SIGNAL(cursorPositionChanged()), this, SLOT(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().width(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 = (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);
                painter.setPen(Qt::black);
                painter.drawText(0, top, lineNumberArea->width(), fontMetrics().height(),
                                 Qt::AlignRight, number);
            }

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