Add ResizableWidget

When manual resizing is enabled, the vertical widget size can be changed
by dragging the widget in the lower right corner.

CMakeLists.txt

@@ -219,6 +219,8 @@ target_sources(
           lib/utils/priority-helper.hpp
           lib/utils/regex-config.cpp
           lib/utils/regex-config.hpp
+          lib/utils/resizable-widget.cpp
+          lib/utils/resizable-widget.hpp
           lib/utils/resizing-text-edit.cpp
           lib/utils/resizing-text-edit.hpp
           lib/utils/resource-table.cpp

lib/utils/resizable-widget.cpp

@@ -0,0 +1,106 @@
+#include "resizable-widget.hpp"
+
+namespace advss {
+
+ResizableWidget::ResizableWidget(QWidget *parent) : QWidget(parent) {}
+
+void ResizableWidget::SetResizingEnabled(bool enable)
+{
+	setMouseTracking(enable);
+	_customHeight = enable ? sizeHint().height() : 0;
+	auto pol = sizePolicy();
+	pol.setVerticalPolicy(enable ? QSizePolicy::Fixed
+				     : QSizePolicy::Preferred);
+	_resizingEnabled = enable;
+}
+
+void ResizableWidget::mousePressEvent(QMouseEvent *event)
+{
+	if (!_resizingEnabled) {
+		QWidget::mousePressEvent(event);
+		return;
+	}
+
+	if (IsInResizeArea(event->pos())) {
+		_resizing = true;
+		_lastMousePos = event->globalPosition().toPoint();
+		event->accept();
+	} else {
+		QWidget::mousePressEvent(event);
+	}
+}
+
+void ResizableWidget::mouseMoveEvent(QMouseEvent *event)
+{
+	if (!_resizingEnabled) {
+		QWidget::mouseMoveEvent(event);
+		return;
+	}
+
+	if (_resizing) {
+		const int dy = event->globalPosition().toPoint().y() -
+			       _lastMousePos.y();
+		const int baseHeight = _customHeight == 0 ? height()
+							  : _customHeight;
+		const int newHeight = baseHeight + dy;
+		_customHeight =
+			std::clamp(newHeight, minimumHeight(), maximumHeight());
+		updateGeometry();
+		_lastMousePos = event->globalPosition().toPoint();
+		event->accept();
+	} else {
+		setCursor(IsInResizeArea(event->pos()) ? Qt::SizeVerCursor
+						       : Qt::ArrowCursor);
+		QWidget::mouseMoveEvent(event);
+	}
+}
+
+void ResizableWidget::mouseReleaseEvent(QMouseEvent *event)
+{
+	if (_resizing) {
+		event->accept();
+		_resizing = false;
+	} else {
+		QWidget::mouseReleaseEvent(event);
+	}
+}
+
+void ResizableWidget::paintEvent(QPaintEvent *event)
+{
+	QWidget::paintEvent(event);
+
+	if (!_resizingEnabled) {
+		return;
+	}
+
+	// Draw a triangle in bottom-right as resize indicator
+	QPainter painter(this);
+	QPolygon triangle;
+	triangle << QPoint(width() - 1, height() - _gripSize)
+		 << QPoint(width() - _gripSize, height() - 1)
+		 << QPoint(width() - 1, height() - 1);
+	painter.setBrush(Qt::gray);
+	painter.drawPolygon(triangle);
+}
+
+QSize ResizableWidget::sizeHint() const
+{
+	if (!_resizingEnabled) {
+		return QWidget::sizeHint();
+	}
+
+	if (_customHeight == 0) {
+		return QWidget::sizeHint();
+	}
+
+	return QSize(width(), _customHeight);
+}
+
+bool ResizableWidget::IsInResizeArea(const QPoint &pos) const
+{
+	return QRect(width() - _gripSize, height() - _gripSize, _gripSize,
+		     _gripSize)
+		.contains(pos);
+}
+
+} // namespace advss

lib/utils/resizable-widget.hpp

@@ -0,0 +1,34 @@
+#pragma once
+#include <QMouseEvent>
+#include <QPainter>
+#include <QWidget>
+
+namespace advss {
+
+class ResizableWidget : public QWidget {
+	Q_OBJECT
+
+public:
+	ResizableWidget(QWidget *parent = nullptr);
+
+protected:
+	void SetResizingEnabled(bool enable);
+	void mousePressEvent(QMouseEvent *event) override;
+	void mouseMoveEvent(QMouseEvent *event) override;
+	void mouseReleaseEvent(QMouseEvent *event) override;
+	void paintEvent(QPaintEvent *event) override;
+	QSize sizeHint() const override;
+	int GetCustomHeight() const { return _customHeight; }
+	void SetCustomHeight(int value) { _customHeight = value; }
+
+private:
+	bool IsInResizeArea(const QPoint &pos) const;
+
+	bool _resizingEnabled = false;
+	bool _resizing = false;
+	QPoint _lastMousePos;
+	int _customHeight = 0;
+	const int _gripSize = 15;
+};
+
+} // namespace advss