Prune active tiles, fixes #3765

[jblarsen]

Please see the discussion here:

#3765

This fixes the issue. But please also see:

#3431

#3513

where the if statement was introduced. I am not sure whether my pull request will reintroduce that bug or if it will have performance implications for the use case with an opacity slider.

[mourner]

I am not sure whether my pull request will reintroduce that bug or if it will have performance implications for the use case with an opacity slider.

Can you check this?

[jblarsen]

Can you check this?

I have used the sample page provided by jplante in issue #3431 to test that the bug is not reintroduced:

Leaflet master:
http://playground-leaflet.rhcloud.com/cuyi/edit?html,console,output

Code with fix:
http://playground-leaflet.rhcloud.com/bod/edit?html,console,output

Please note that the links will not work forever since the js and css files are not uploaded to a unique and persistent URL.

I will try to make two examples with an opacity slider to see what happens with the two versions.

[jblarsen]

I have made a version in which you can check out how many calls are made to the _pruneTiles method when you change the opacity:

http://playground-leaflet.rhcloud.com/kom/1/edit?html,console,output

It is only called once per opacity change (which it should). This is the same as without the change I suggest.