Issue 3892 - Disable button if input is invalid when adding subscriptions or filters

options.html

Index: options.html
===================================================================
--- a/options.html
+++ b/options.html
@@ -312,7 +312,7 @@
                       </template>
                     </ul>
                     <form id="custom-filters-add" class="controls">
-                      <input type="text"/>
+                      <input type="text" required="true" pattern=".*\S.*"/>
                       <button class="i18n_options_button_add" type="submit"></button>
                     </form>
                   </div>
@@ -403,7 +403,7 @@
           <div class="dialog-content-block">
             <div>
               <label for="blockingList-textbox" class="i18n_options_dialog_custom_subscription_title"></label>
-              <input id="blockingList-textbox" type="text" class="default-focus" placeholder="www.example.com/blockinglist.txt" />
+              <input id="blockingList-textbox" type="url" required="true" pattern="https?://.+" class="default-focus" placeholder="https://example.com/blockinglist.txt" />

[Sebastian Noack, 2016/04/06 22:46:01]

Two notes here:

1. type=url only checks whether there is a protocol delimiter with at least on
non-whitespace character before and after it. Therefore the additional pattern
which is consistent with the behavior on the old options page.
2. The placeholder previously indicated an URL with omitted protocol part.
Regardless of the new validation, this simply doesn't work with the current
implementation.

             </div>
             <button class="i18n_options_dialog_custom_import" data-action="import-subscription"></button>
           </div>