Allow default Panelizer to be selected

Step 1: Use a variable to select the default loaded on the node-edit page.

This patch provides both the logic to select the default and assign it, adds a new 'default panel' item to the settings instead of creating a new variable, and defaults to the normal "{entity_type}:{bundle}:default" panel to retain complete backwards compatibility.

I'm particularly interested to know if there are specific use cases that aren't covered for or possible glitches.

Might it be worth improving the UX to indicate on the overview page which display is the default?

Tagging that this could use a usability review.

FYI this is what it looks like:

This is an updated patch that goes back to using variables to control which display is used, allowing the selection to be exported.

Rerolled.

Missed a few variables when I changed he separator to a colon instead of a single underline.

This needs some work:

• Allow no default to be selected.
• Changing handling of the "Provide default panel" & rename it ("Provide initial display") so it only generates a display, it doesn't override this new setting.
• Indicate the storage status of each one (just 'cause).
• Update help message to make it clear how this plays with the others.

This has been updated to include the changes noted in #15. I've realized that this changes things slightly, the creation of a 'default' display is now different to the selection of the default.

This resolves a problem with the patch in #15 where selecting "Do not assign a default" made no difference on the entity form selector.

With the patch in #16 this is what the content type options look like:

The node form then has the following selector:

The gotcha right now is the upgrade process. I think this needs an update script to identify any entities / bundles that have the "default display" option enabled and assign it as the default via the new variable.

Any thoughts?

Items to debate:

1. Do we need an option to control whether each an item must be displayed? I think we do.
2. Shouldn't the entity form always have the "-- No panel --" (option unless we require one be selected)? I think so.
3. If the user selects the default display should the panelizer_entity record be saved to note this? If so, what if the default display is changed later on, should the old records also be updated later on or should the system lock those older records to the older display? My guess is that default values should not be saved and that older "default display" nodes should adapt the new default.
4. Is an update script needed to assign the new "default" variable for any entity/bundle that has the previous "default display" option enabled? I think so.

I have an idea on how to change this so it is completely backwards compatible and wouldn't need an update script. I'll try to get to it this week.

Ok, I've realized there's a problem. Each entity currently tracks which display is being used; this selection saved in the {panelizer_entity} table. The problem is that it saves the full name of the display, e.g. "node:article:default", rather than just "default", so if the default is changed via this new option, any entity that was using the default will not be updated to the new default. What we'll need to do instead is change the default handling to store a placeholder value, e.g. "default" and then have the display loading logic identify the appropriate default at loading time.

I've got the current patch tidied up, but I need to update it to handle the placeholder, and add an update script to fix existing records.

Just so I don't accidentally loose it, WIP that needs to have the placeholder functionality added.

Related: #1965148: Load the full Panelizer default object - this would stop saving records if the default is selected, and simplify the work on this issue.

I hadn't uploaded this before, I thought I'd better before I accidentally loose the changes again. It still needs work =)

Now that the default value handling is being taken care of by another issue, this becomes much simpler.

This version adds a small little UX improvement to indicate in each selector on add_bundle_settings_form and settings_form which one is the current default.

It'd be nice to be able to indicate on the settings overview page which display is the current default, but I don't know if there's an easy way to tap into ctools_export_ui->list_page without just duplicating the whole function.

Removing the "usability review" tag as the default display aspect is no longer being handled by it.

This fixes a bug where I forgot to define an $options array, and removes a todo comment for something that now works.

Needed a change in hook_entity_load() to use the new variable (must have missed it during a reroll). Also, add_bundle_setting_form_submit() was updated so that if EntityCache is installed it will clear the caches if the default is changed, that way all such entities will have their display reloaded.

This needs some work, I was having some problems with it this morning, so something must have been lost again during the reroll.

Rerolled, along with some fixes and testing.

Rerolled.

Some small UX improvements around the default selector.

Contains a minor tweak to fix the problem that creating new entities did not select the correct default, and there's no reason to add "(selected)" to the previously selected item when editing an entity.

Interdiff for patch #36.

A minor wording tweak in add_bundle_setting_form().

Committed. There are several related issues slated for v3.2 (see #2155813: Plan for Panelizer 7.x-3.2 release) that will help simplify the UX around this.