codeedit.cpp

#include <QWidget>
#include <QPlainTextEdit>
#include <QPaintEvent>
#include <QResizeEvent>
#include <QPainter>
#include <QTextBlock>
#include <QPen>
#include "codeedit.h"


class LineNumber : public QWidget
{
public:
    LineNumber(CodeEdit *editor) : QWidget(editor),codeEditor(editor)
    {}

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

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

private:
    CodeEdit *codeEditor;
};


CodeEdit::CodeEdit(QWidget *parent) :
    QPlainTextEdit(parent)
{
    lineNumberArea = new LineNumber(this);
    connect(this, &CodeEdit::blockCountChanged, this, &CodeEdit::updateLineNumberAreaWidth);
    connect(this, &CodeEdit::updateRequest, this, &CodeEdit::updateLineNumberArea);
    connect(this, &CodeEdit::cursorPositionChanged, this, &CodeEdit::highlightCurrentLine);

    updateLineNumberAreaWidth(0);
    highlightCurrentLine();
}

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

    int space = 4 + fontMetrics().horizontalAdvance(QLatin1Char('9')) * digits;

    return space;
}

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

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

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

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

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

        QColor lineColor = QColor("#fcefcd");
        lineColor.setAlpha(50);

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

    setExtraSelections(extraSelections);
}

void CodeEdit::lineNumberAreaPaintEvent(QPaintEvent *event)
{
    QPen pen("#f5f5f5");
    pen.setWidth(4);
    QPainter painter(lineNumberArea);
    painter.fillRect(event->rect(), "#0f4851");
    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(pen);
            painter.drawText(0, top, lineNumberArea->width(), fontMetrics().height(), Qt::AlignCenter, number);
        }

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