'p5 WEB' sometimes does not show

p5.js Coding Questions
1

‘p5 WEB’ sometimes does not show.

fig
fig772×809 119 KB 

//-> setup
var cbox;
cbox = select('#map_div'); cbox.position(10,160); cbox.hide();
//-> button event
cbox.show();

When the ‘cbox.show()’ operation is performed, the map should be visible, but sometimes it is not visible. Why?
It is invisible, but can be seen by moving the ‘mouse-wheel’ over the area.

  1. I used ‘show’, but the map is not visible.
  2. If you use the ‘mouse-wheel’ on that area, the map will be visible.
    Why? What’s the matter?