User Preferences: Added "Enabled add-ons only" preference

This checkbox replaces the "Disabled" and "Enabled" entries in the
filter drop-down. As a result, it now takes a single click to limit the
shown entries to enabled add-ons only. This is also an actual flag in
the preferences, and thus its state is saved between runs on Blender (in
contrast to the filter, which is always reset to "All").

Reviewed by: brecht, billreynish

release/scripts/startup/bl_ui/space_userpref.py

@@ -1744,6 +1744,7 @@ class USERPREF_PT_addons(Panel):
         row.operator("preferences.addon_refresh", icon='FILE_REFRESH', text="Refresh")
 
         row = layout.row()
+        row.prop(context.preferences.view, "show_addons_enabled_only")
         row.prop(context.window_manager, "addon_filter", text="")
         row.prop(context.window_manager, "addon_search", text="", icon='VIEWZOOM')
 
@@ -1770,6 +1771,7 @@ class USERPREF_PT_addons(Panel):
                 "(see console for details)",
             )
 
+        show_enabled_only = context.preferences.view.show_addons_enabled_only
         filter = context.window_manager.addon_filter
         search = context.window_manager.addon_search.lower()
         support = context.window_manager.addon_support
@@ -1786,13 +1788,15 @@ class USERPREF_PT_addons(Panel):
                 continue
 
             # check if addon should be visible with current filters
-            if (
-                    (filter == "All") or
-                    (filter == info["category"]) or
-                    (filter == "Enabled" and is_enabled) or
-                    (filter == "Disabled" and not is_enabled) or
-                    (filter == "User" and (mod.__file__.startswith(addon_user_dirs)))
-            ):
+            is_visible = (
+                (filter == "All") or
+                (filter == info["category"]) or
+                (filter == "User" and (mod.__file__.startswith(addon_user_dirs)))
+            )
+            if show_enabled_only:
+                is_visible = is_visible and is_enabled
+
+            if is_visible:
                 if search and search not in info["name"].lower():
                     if info["author"]:
                         if search not in info["author"].lower():