Qt实例——代码编辑器
⽬录
概述
窗体包含两个部分，左侧的⾏号显⽰区(LineNumberArea)和右侧的代码编辑区(CodeEditor)。其中CodeEditor为主窗体，继承⾃QPlainTextEdit；LineNumberArea为⾏号显⽰区，继承⾃QWidget。
LineNumberArea
class LineNumberArea : public QWidget
{
public:
LineNumberArea(CodeEditor *editor) : QWidget(editor) {
codeEditor = editor;
}
//返回合适的窗体⼤⼩
QSize sizeHint() const override {
return QSize(codeEditor->lineNumberAreaWidth(), 0);
}
protected:
//重写绘制函数，调⽤CodeEditor的⽅法
void paintEvent(QPaintEvent *event) override {
codeEditor->lineNumberAreaPaintEvent(event);
}
private:
CodeEditor *codeEditor;
};
组合了CodeEditor类，构造时作为参数传⼊，控制⾏号窗体的⼤⼩及显⽰内容。
CodeEditor
class CodeEditor : public QPlainTextEdit
{
Q_OBJECT
public:
CodeEditor(QWidget *parent = nullptr);
void lineNumberAreaPaintEvent(QPaintEvent *event);
int lineNumberAreaWidth();
qt viewportprotected:
void resizeEvent(QResizeEvent *event) override;
private slots:
void updateLineNumberAreaWidth(int newBlockCount);
void highlightCurrentLine();
void updateLineNumberArea(const QRect &, int);
private:
QWidget *lineNumberArea;
};
CodeEditor::CodeEditor(QWidget *parent) : QPlainTextEdit(parent)
{
lineNumberArea = new LineNumberArea(this);
//每当按下回车或者删除回车(更新字符块)，则newBlockCount计数，并触发该信号, newBlockCount 默认为1    connect(this, &CodeEditor::blockCountChanged, this, &CodeEditor::updateLineNumberAreaWidth);
connect(this, &CodeEditor::updateRequest, this, &CodeEditor::updateLineNumberArea);
//光标改变时发出信号
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 (ains(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 = ();
top = bottom;
bottom = top + (int) blockBoundingRect(block).height();
++blockNumber;
}
}
参考

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