add mapWidget demo

CMakeLists.txt

@@ -20,6 +20,8 @@ set(PROJECT_SOURCES
         src/localGameDialog/localGameDialog.cpp
         src/localGameDialog/localGameDialog.h
         src/localGameDialog/localGameDialog.ui
+        src/mapWidget/mapWidget.cpp
+        src/mapWidget/mapWidget.h
         res/res.qrc
 )
 

src/mapWidget/mapWidget.cpp

@@ -0,0 +1,31 @@
+#include "mapWidget.h"
+#include <QPainter>
+#include <QWheelEvent>
+
+MapWidget::MapWidget(QWidget* parent) :
+    QWidget(parent), scale(1.0), offset(0, 0) {
+    setFixedSize(800, 600);
+}
+
+MapWidget::~MapWidget() {
+}
+
+void MapWidget::paintEvent(QPaintEvent* event) {
+    QPainter painter(this);
+    painter.translate(offset);
+    painter.scale(scale, scale);
+    painter.setBrush(Qt::red);
+    // demo rect
+    painter.drawRect(50, 50, 200, 100);
+}
+
+void MapWidget::wheelEvent(QWheelEvent* event) {
+    int delta = event->angleDelta().y();
+    float factor = (delta > 0) ? 1.1 : 0.9;
+    QPoint globalMousePos = QCursor::pos();
+    QPoint widgetMousePos = mapFromGlobal(globalMousePos);
+    QPointF oldMousePos = (widgetMousePos - offset) / scale;
+    scale *= factor;
+    offset = widgetMousePos - oldMousePos * scale;
+    update();
+}

src/mapWidget/mapWidget.h

@@ -0,0 +1,23 @@
+#ifndef MAPWIDGET_H
+#define MAPWIDGET_H
+
+#include <QWidget>
+#include <QPointF>
+
+class MapWidget : public QWidget {
+    Q_OBJECT
+
+   public:
+    explicit MapWidget(QWidget* parent = nullptr);
+    ~MapWidget();
+
+   protected:
+    void paintEvent(QPaintEvent* event) override;
+    void wheelEvent(QWheelEvent* event) override;
+
+   private:
+    float scale;
+    QPointF offset;
+};
+
+#endif  // MAPWIDGET_H