Draw and event position relative to parent (for pages)

include/gui/ScrollablePage.hpp

@@ -0,0 +1,21 @@
+#pragma once
+
+#include "Page.hpp"
+
+namespace gsr {
+    class ScrollablePage : public Page {
+    public:
+        ScrollablePage(mgl::vec2f size);
+        ScrollablePage(const ScrollablePage&) = delete;
+        ScrollablePage& operator=(const ScrollablePage&) = delete;
+
+        bool on_event(mgl::Event &event, mgl::Window &window, mgl::vec2f offset) override;
+        void draw(mgl::Window &window, mgl::vec2f offset) override;
+
+        mgl::vec2f get_size() const { return size; }
+    private:
+        float get_border_size(mgl::Window &window) const;
+    private:
+        mgl::vec2f size;
+    };
+}