Warn when map container's width or height are zero

[ahocevar]

Fixes #11984.

I think it makes sense to let the user know why no map is visible in the non obvious case where the container's width or height is 0.

[MoonE]

Thanks, @ahocevar, not seeing a map because the container had zero height is probably a common problem.

[AndreaSGI]

Thanks, @ahocevar, not seeing a map because the container had zero height is probably a common problem.

How to handle a case when the Map container is hidden (in my case it is not visible because it is in another tab), and the initialization gives this error?

[MoonE]

This should befixed in the next version by #12632, until then you can simply ignore it.

[AndreaSGI]

@MoonE I can ignore the warning, but I cannot ignore the empty div without the map rendered 😄

[MoonE]

The warning message is working as expected when the map is not displayed. Once the map is displayed it should render to the configured target.
How are you expectation it to work / what is not working for you?
You may need to call updateSize once when your map tab becomes visible.