Hi and thanks for your replies.
Maybe my link is wrong or for another purpose...
Right now, the center and the zoom level seem to be set on page load.
If I resize the browser window or change the orientation of the tablet or phone, some markers are then outside of the viewport because the center and the zoom level of the map don't change on window resize.
I have to do a page reload with the new windows size or device orientation for the markers and zoom level to fit again.
I did a short screen capture, where I do a page reload after each resize...that is the behaviour I am looking for:
www.cleverworx.de/video/resizing.mov
That's why I thought, maybe some kind of "on window resize" listener might be able to do that and "recalculate" the center and zoom level, each time the window size or orientation changes.