Visually encapsulate the content listing filter to distinguish it from the 'add content' action link

I guess we should do the same for "add people" in the people adminitration page (/admin/people)

I can't figure out how to add a fieldset there, for this specific view filter. However it would be easy with CSS.

Hum... my solution looks more like a hack, but it works, and it seems it doesn't break the tests.
Any hints appreciated !

I moved the submit button inside the fieldset as well (both Apply and Reset).
But again, it must be improved !

I didn't succeed to troubleshoot the tests.. And the fieldset is applied for any views filter..With many impacts, and maybe.. bugs.
So I think there is a better solution : CSS. No impact. And the result is the one we want.

Here is the patch, without interdiff, cause it is a new one.

Ha, I like the fact that we might just need to use CSS, not sure though whether this would be okay accessibility wise.
@pguillard Do you maybe know more about that?

+++ b/core/modules/views/src/Form/ViewsExposedForm.php
@@ -80,6 +80,12 @@ public function buildForm(array $form, FormStateInterface $form_state) {
+    $form['filter'] = array(
+      '#type' => 'fieldset',
+      '#title' => t('Filter'),
+      '#collapsible' => TRUE,
+      '#collapsed' => FALSE,
+    );

I certainly think we should not add a fieldset to the markup for all views. This is a special case potentially here

In terms of accessibility, I guess we bring nothing and remove nothing.

Looks that way. Seems like a good UX improvement though.

I would say RTBC ?

@LewisNyman : should I go for #14 or wait for the pane task and #15 ?

This same issue came up again today in another usability test at UMN.

A new patch with extra CSS in classy/css/exposed-filters.css which I think is much better (Anyway #9 was not applying anymore).
I could also add an extra class, "views-exposed-wrapper" for instance.

i've applied patch #18, the interface looks now much more clear

BEFORE

AFTER

I looked at how field sets are used elsewhere in core admin and I'm only finding collapsible ones. Even found a similar interface for URL aliases:

(I don't think the blue Filter button is a good idea there)

So maybe we should make this a collapsible fieldset as well with a title of "Filter content".

Also, i would include the below section «with selection» into the fieldset or would create another fieldset for this.

The title of the first fieldset would be «FILTER CONTENT», as stated @yoroy
The title of the second fieldset would be «MODIFY CONTENT»

I just try to revive this issue :

So #18 was made with CSS changes
I got back to #7 with a form filter.

Tets will not pass, but it should be slightly better..

I am working on this issue at Drupalcon Dublin. Reconfiguring initial GIT configuration (I cloned 8.3.x., at the sprint. According to documentation I need to be working off of 8.3.0-dev. Submitting patch to this issue or to https://www.drupal.org/node/2785051 by COB today Saturday Oct.1.)

Patch submitted on other "similar issue" - https://www.drupal.org/node/2785051 - This current issue remains.

I'd like to pospone the development here until a generic & integrated design for VBO and filters has been decided. See #2721807: Design for filters and bulk operations.

Since the design has been reviewed in #2721807: Design for filters and bulk operations, together with the new design for VBO, this issue can continue.

Addressed in #3329996: Claro bulk operation form has been redesigned