How to disable page's title in wp-admin from being edited? - wordpress

Question

I have a wp-network installed with users that can create pages in each site.
Each of those pages get a place in the primary menu, and only one user have permission to create all this menu.
I want to create a user only to be able to edit the content of the pages, but not the title.
How can I disable the title of the page to be edited from the admin menu for a specific user, or (far better) for a capability?
I thought only a possibility, that's editing admin css to hide the title textbox, but I have two problems:
I don't like to css-hide things.
I don't know where is the admin css.
I know php, but don't know how to add a css hide to an element for a capability.

Answer 1

You should definitely use CSS to hide the div#titlediv. You'll want the title to show in the markup so the form submission, validation, etc continues to operate smoothly.
Some elements you'll need to know to implement this solution:
current_user_can() is a boolean function that tests if the current logged in user has a capability or role.
You can add style in line via the admin_head action, or using wp_enqueue_style if you'd like to store it in a separate CSS file.
Here is a code snippet that will do the job, place it where you find fit, functions.php in your theme works. I'd put it inside a network activated plugin if you're using different themes in your network:
<?php
add_action('admin_head', 'maybe_modify_admin_css');
function maybe_modify_admin_css() {
if (current_user_can('specific_capability')) {
?>
<style>
div#titlediv {
display: none;
}
</style>
<?php
}
}
?>

Answer 2

I resolved the problem, just if someone comes here using a search engine, I post the solution.
Doing some research, I found the part of the code where the title textbox gets inserted, and I found a function to know if a user has a certain capability.
The file where the title textbox gets added is /wp-admin/edit-form-advanced.php. This is the line before the textbox
if ( post_type_supports($post_type, 'title') )
I changed it to this
if ( post_type_supports($post_type, 'title') and current_user_can('edit_title') )
That way, the textbox is only added when the user has the capability called "edit_title"
When this IF block ends few lines after, I added:
else echo "<h2>".esc_attr( htmlspecialchars( $post->post_title ) )."</h2>";
To see the page title but not to edit it, when the user hasn't got "edit_title" capability.
Then I had already installed a plugin to edit user capabilities and roles, wich help me to create a new capability (edit_title) and assign it to the role I want.