diff --git a/codeeditor.cpp b/codeeditor.cpp
new file mode 100644
index 0000000000000000000000000000000000000000..aca02d587e7d56d791f24d0fe44fb538c3c2af8c
--- /dev/null
+++ b/codeeditor.cpp
@@ -0,0 +1,102 @@
+#include <QPainter>
+#include <QTextBlock>
+#include "codeeditor.h"
+#include "linenumberarea.h"
+
+CodeEditor::CodeEditor(QWidget *parent) :
+    QPlainTextEdit(parent)
+{
+    lineNumberArea = new LineNumberArea(this);
+
+    connect(this, SIGNAL(blockCountChanged(int)), SLOT(updateLineNumberAreaWidth(int)));
+    connect(this, SIGNAL(updateRequest(QRect,int)), SLOT(updateLineNumberArea(QRect,int)));
+    connect(this, SIGNAL(cursorPositionChanged()), 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;
+    }
+}
\ No newline at end of file