Start testing adding an immediate-mode node element

include/ui.h

@@ -37,6 +37,8 @@ struct ui_ctx {
   i64 active;
   i64 mouse_x;
   i64 mouse_y;
+  i64 rel_x;
+  i64 rel_y;
   bool mouse_down;
   bool mouse_up;
   const window_t *wnd;
@@ -47,5 +49,6 @@ void reset_ui_ctx(ui_ctx_t *ctx);
 void handle_ui_events(const window_t *wnd, ui_ctx_t *ctx,
                       const SDL_Event *event);
 bool button(const window_t *wnd, ui_ctx_t *ctx, rect_t rect);
+rect_t node(const window_t *wnd, ui_ctx_t *ctx, rect_t rect);
 
 #endif // !UI_H