Fix WYSIWYG metaboxes saving

[youknowriad]

closes #7176

This is the exact same fix I've applied before in #8762 but in my testing this time it works properly and fixes the issue consistently. I tested using @danielbachhuber's snippet here #7176 (comment)

[danielbachhuber]

but in my testing this time it works properly and fixes the issue consistently

Were you able to finally reproduce the issue consistently?

[youknowriad]

Yes, I was. I'd appreciate other people testing too because I don't really understand what happens the first time we tried this :)

[youknowriad]

After some testing in #7176 It looks like this PR fixes the issue if you are on 5.0 RC. I don't have the full explanation yet. Maybe it has something to do with how TinyMCE initialization work but also would happy to land it as is. As 5.0RC is our most important target.

[ideadude]

When I checkout the fix/metabox-saving branch and reinstall/build, this does NOT fix the issue for me. I'm on 4.9.9-alpha-43656 via the beta tester plugin. Does this count as 5.0 RC?

The CMB2 fix does work for me. I can work on a PR that merges the two approaches.

[ideadude]

Running tinymce.triggerSave(); doesn't work for my test.

When I looked into this earlier, it seemed like WP was adding some kind of check that would skip the save if the main tinymce editor was on the text tab, but this would skip all of the editors on the screen. Something like that.

When I swap the triggerSave line for the relevant code from CMB2 fix (similar to code I shared on another issue somewhere), it works:

for (var i = 0; i < window.tinymce.editors.length; i++) {
  window.tinymce.editors[i].save();
}

Feel free to update your PR or let me know if it would help if I did a separate PR with this version. Whatever will get the fix done fastest.

[youknowriad]

Please if you have some time, let's open a separate PR :). Thanks for your help figuring this out.

[ideadude]

Working on it. Coming in soon. I'll link it from here.

[ideadude]

Here is my alternative PR: #12568

Other testers would be appreciated.

Let me know if you need anything else from me.

[youknowriad]

closing in favor of #12568