update main widget to CodeEditor with line numbers and highlight. Open file from command line.

tools/lammps-gui/codeeditor.cpp

@@ -0,0 +1,102 @@
+#include "codeeditor.h"
+#include "linenumberarea.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::AlignRight, number);
+        }
+
+        block  = block.next();
+        top    = bottom;
+        bottom = top + qRound(blockBoundingRect(block).height());
+        ++blockNumber;
+    }
+}