Preserve original $content variable in template_preprocess_panels_pane()

Changing the $content variable mid-stream would probably change people's templates, and that would lead to problems. So I don't think we can actually do that.

We can possibly rename the original $content variable so that it is preserved.

You *can* override the original template preprocess. In hook_theme, you can set this:

'override preprocess functions' => TRUE. Your theme can actually implement hook_theme() and set that for that and then NO preprocess functions except the theme's get called. (You can, then, if you like, call back to whichever ones you wish to use).

I'm not sure that Panels is likely to change anything here.

I think it would be good to somehow preserve the original content variable so you have easy access to things like module, type, subtype, which are very likely useful to themers.

Another thing worth noting though based on the original post is that I recommend not doing this (steps 3 & 4):

When you override template_preprocess_panels_pane() in your own theme, weirdness ensues when you just copy/paste and start altering anything which uses the $content variable within the provided function body. i.e. adding a another variation to the theme_hook_suggestions array.

When you override a theme function you generally copy and paste the original function and then modify it to your liking.
When you are using template preprocess functions though this is not a good idea.
With a theme function override your function is replacing the original, however with a template preprocessor your function is running after the original (and potentially there are also others in addition to yours and the original) so you are modifying the existing variables array, not writing it from scratch.
It is not uncommon that if you copy and paste a preprocess function like that you will run into problems.

I recommend starting with an empty preprocess function, then if you do need to re-run parts of code from the original template_preprocess function just take those parts as required (they may need slight changes to account for the fact that they have already run once).

Here is a patch that does it, with a few notes:

1. I took the liberty of naming the variable, but someone who knows the panels/ctools plugin system better may have a better suggestion for that.
2. I removed the duplicate content but if it is decided it is better to leave it I can make that change.
3. I wasn't sure if it was possible for $content->content to be initially unset so I put a check anyway. The check may not be necessary.

Whoops.
Same patch except using clone to copy the object.

At first I could not understand why I could not have my custom panel style pass through both template_preprocess_panels_pane and my own preprocess function.
It turned out that the template_preprocess_panels_pane altered the data structure as described in this issue, causing my preprocess function to fail if it had run after template_preprocess_panels_pane.

Rooby, I tried your patch. While your solution would have allowed me to work around it, I don't think it is the proper way to fix this.

I think the solution might be much easier: keep the data structure in template_preprocess_panels_pane in tact and move the collapsing of $vars['content'] to a process function. That way you can have as many preprocess functions running in sequence as you want.

I've attached a patch as a proof of concept. A few quick checks seem to confirm this works as expected.

Hopefully fixed the patch.

Updated patch: Missed a line of code in the process function.

A possible downside of this approach is that it could break existing preprocess functions that people may have written that rely on the variables as they currently are.
So this solution would at least have to come with a notice for people to check their custom code.

This solution also still suffers in some ways from the same problem it is trying to solve because it is still overwriting the original $vars['content'].

With this patch if someone wants to use the original content in hook_process_panels_pane() or the template file then they will still have the problem.

Rooby, you are right, that might be an issue.

However since in the current situation it is pretty useless to have another preprocess function running after the original template_preprocess_panels_pane function I think the real world impact might be small.
For people who completely override the template_preprocess_panels_pane function it also shouldn't be an issue.

It doesn't really matter how useless it might be, people still could be doing it and panels is used by a very large amount of people and is extended by a number of other modules, so we need to exercise caution.

There is also still the matter of the problem not being fixed for the use of hook_process_panels_pane() and the use of the original content in the template file.

With this patch it would be possible for a person to add their own code in hook_preprocess_panels_pane() to get the original content for use later on but it would be better if the panels module did this so it was consistent for everyone.

In the end I see multiple potential issues with that approach.

The only possible issue with the other approach is that it will use a little more memory.
I don't think that it would be enough to cause concern but it could be benchmarked if anyone was worried.