update tile & metatile usage counts automatically when painting

include/ui/eventfilters.h

@@ -26,3 +26,16 @@ signals:
     void wheelZoom(int delta);
 public slots:
 };
+
+
+
+/// Emits a signal when a window gets activated / regains focus
+class ActiveWindowFilter : public QObject {
+    Q_OBJECT
+public:
+    ActiveWindowFilter(QObject *parent) : QObject(parent) {}
+    virtual ~ActiveWindowFilter() {}
+    bool eventFilter(QObject *obj, QEvent *event) override;
+signals:
+    void activated();
+};

include/ui/tileseteditor.h

@@ -57,6 +57,7 @@ public slots:
     void onSelectedMetatileChanged(uint16_t);
 
 private slots:
+    void onWindowActivated();
     void onHoveredMetatileChanged(uint16_t);
     void onHoveredMetatileCleared();
     void onHoveredTileChanged(uint16_t);