Qt 5.9 | Qt Widgets | Code Editor Example | codeeditor.cpp Example File

Qt 5.9.9 Reference Documentation

# codeeditor.cpp Example File

widgets/codeeditor/codeeditor.cpp

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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;
          }
      }