Provide hook_preprocess_link() to Drupal 5

The contents of the flag link are more complicated than hook_link() normally allows, so we actually manually generate the link then put the entire completed result into $link['title'] and set $link['html'] = TRUE. You can change this links contents by overriding theme_flag(). Note that overriding this function is a bit unusual though, since Flag for Drupal 5 is a backport from Drupal 6. You'll need to copy theme_flag() into your template.php, then copy flag.tpl.php into your theme directory and update the theme function to use the .tpl.php file in your theme.

I realized you're actually wanting to affect the link from a *module* which makes this whole ordeal quite a bit more difficult, since Drupal 5 doesn't have hook_preprocess().

So to get around that problem, here's a patch that provides hook_preprocess_link() to Drupal 5, so you can alter the variables before they are sent to the flag.tpl.php file.

+1

This is a feature I too wanted, for two reasons:

1. This will make it possible to write a "Flag image" module (instead of this how-to).

2. This will simplify some how-to's: we won't need to provide an appendix for D5 users.

Some comments on the patch:

- Won't module_implements('preprocess_flag') be faster? It caches the results.

- I wish we could prepend the list with the engine's and the theme's preprocess functions as well (or else "2. This will simplify some how-to's" won't apply).

- Since the code repeats in two places, it'd be nice to factor it out.

- Perhaps, in the second hunk, it'd be good to move the $suggestions to the $variables (and rename it to $template_files) so it could be added to (in a preprocess function).

Yeah module_implements would probably be better since it's likely we'll be doing this multiple times per page. This patch uses module_implements and creates a dedicated function for calling preprocess functions.

However, I don't add in the 'template_files' suggestions or call preprocess functions in the theme layer. These shouldn't be necessary since phptemplate already provides _phptemplate_variables() in Drupal 5 for these purposes. This patch only backports the ability to preprocess variable in the module layer, since there is no Drupal 5 equivalent without it.

@quicksketch, I agree with all your points.

@sirkitree, do you happen to use PHP4?

(it's nice to know that our module still works with PHP4 ;-)

The manual page for call_user_func says "Note that the parameters for call_user_func() are not passed by reference". I think it means that the called function won't be able to modify $variables. Could you change it to the following pattern instead?

$function = $module .'_preprocess_'. $hook;
$function($variables);

Here's the patch with the change mentioned in #12 done. In addition, the call to template_preprocess_flag() isn't hardcoded now, because the function gets a $hook paramter.

Committed. Thanks mooffie and sirkitree for the reviews and fixes. Apologies for trying to get fancy with my curly braces ;)