Add a lazy load formatter

This looks awesome. Lets add at least one entry to FieldOutputTest and then we're good to go.

+++ b/tests/src/FunctionalJavascript/LazyLoadFormatterTest.php
@@ -0,0 +1,52 @@
+use Drupal\local_testing\LocalTestingTrait;
...
+  use LocalTestingTrait;

Left over?

Head is fixed. #2888653: Fix HEAD

I applied against the dev version but getting some php error... Is this working ? Do I need to apply the "Fix Head" patch too ?

The other patch is already merged. You should be able to do a pull and then apply the patch. It's helpful to post the error you are getting if you're asking for help in fixing it :)

Edit : Unrelated error. Decluttering the thread...

Video embed field isn't in your callstack, so unlikely to be the issue. Have you removed the "photoswipe" without uninstalling it first?

I thought the patch could have broken something with formatters... I ended up removing and reinstalling photoswipe and the error is gone, weird. Got it working now ! Gotta fix my css but this look very promising. Thank you very much for the help ;)

That patch is perfectly working work me, in the all the views I had the video embed formatter... Works across the board in all my tests. Thanks again !

Clearly lots of demand for a formatter like this. I'll look at #4 and get this in when I can.

Fixing #4 and resolving some issues I had with manual testing.

Explaining some of the changes.

1. +++ b/css/video_embed_field.responsive-video.css
   @@ -28,6 +28,10 @@
   +.video-embed-field-lazy img {
   +  width: 100%;
   +}
   

   This was required because for image styles smaller than the width of the container the video was in, the play button would appear off centre. Stretching the image seems appropriate, the container can either be made smaller or the image style can be made larger.

2. +++ b/src/Plugin/Field/FieldFormatter/LazyLoad.php
   @@ -121,7 +121,6 @@ class LazyLoad extends FormatterBase implements ContainerFactoryPluginInterface
                'video_embed_field/lazy-load',
   -            'video_embed_field/responsive-video',
   
   +++ b/video_embed_field.libraries.yml
   @@ -2,14 +2,15 @@ colorbox:
    lazy-load:
      js:
        js/video-embed-field.lazyLoad.js: {}
   ...
   +    - video_embed_field/responsive-video
   

   Lazyload doesn't work without responsive-video, so enforcing this at the library level instead of adding both.

3. +++ b/video_embed_field.libraries.yml
   @@ -2,14 +2,15 @@ colorbox:
   -    - core/jquery
   -    - core/jquery.once
   +    - system/drupal.system
   

   Viewing as logged out user, it said "Drupal" wasn't defined. This seems like the right library to make sure all the stuff we need is there.

Re-enabling tests I disabled in the last patch.

Hello, is that possible for the lazy load formatter to replace the image thumbnail with the actual video iframe?

edit:
as usual check for js errors before issuing a comment, the formatter works as intended!