Pull Request for Issue #46748

Summary of Changes

This PR implements a category visibility constraint feature that allows site administrators to limit the category dropdown in article editing forms to show only a specific category and its subcategories.

Changes:

• Add scope_root parameter to CategoryeditField for filtering categories using nested set model
• Update HtmlView to pass category scope from menu params to the article form
• Add limit_category_scope option to Create Article menu item configuration
• Add language strings for new parameter (en-GB)
• Implements nested set filtering (lft/rgt) for efficient category dropdown filtering
• Improves usability for sites with many categories

Files Modified:

• administrator/components/com_categories/src/Field/CategoryeditField.php - Core filtering logic
• components/com_content/src/View/Form/HtmlView.php - Pass scope parameter
• components/com_content/tmpl/form/edit.xml - Menu item configuration
• administrator/language/en-GB/com_content.ini - Language strings

Testing Instructions

1. Setup test environment:

   • Create a category hierarchy: "Events" (parent) → "Day 1", "Day 2", "Day 3" (children)
   • Create other unrelated top-level categories (e.g., "News", "Blog")

2. Create menu item with scope limiting:

   • Navigate to Menus → Main Menu → Add New Menu Item
   • Menu Item Type: Articles → Create Article
   • Set "Specific Category" to Yes
   • Choose "Events" category
   • Set "Limit Category Scope" to Yes (new option)
   • Save

3. Test frontend article creation:

   • Navigate to the menu item on the frontend
   • Click to create a new article
   • Open the Category dropdown
   • Verify: Only "Events", "Day 1", "Day 2", "Day 3" appear
   • Verify: "News", "Blog" and other categories do NOT appear

4. Test with scope limiting disabled:

   • Edit the same menu item
   • Set "Limit Category Scope" to No
   • Navigate to frontend and create article
   • Verify: All categories appear (default behavior)

5. Test permission interaction:

   • Create a user with limited category permissions
   • Verify: Both permission filtering AND scope filtering apply (intersection)

Actual result BEFORE applying this Pull Request

When creating articles via a "Create Article" menu item:

• The category dropdown shows ALL categories the user has permission to edit
• On sites with hundreds of categories, this creates a very long, unwieldy dropdown
• Users must scroll through many irrelevant categories to find the correct one
• High risk of selecting the wrong category
• Poor user experience for content editors

Expected result AFTER applying this Pull Request

When creating articles via a "Create Article" menu item with "Limit Category Scope" enabled:

• The category dropdown shows ONLY the menu item's selected category and its subcategories
• Significantly shorter, more manageable dropdown lists
• Editors can quickly find and select the appropriate category
• Reduced cognitive load and faster article creation
• Improved user experience, especially for sites with large category hierarchies

Backwards Compatibility:

• Feature is optional and defaults to disabled
• Existing menu items are unaffected
• No breaking changes

Link to documentations

Please select:

• Documentation link for docs.joomla.org: (Documentation PR to be created after merge)

• No documentation changes for docs.joomla.org needed

• Pull Request link for manual.joomla.org: (Manual PR to be created after merge)

• No documentation changes for manual.joomla.org needed