Switch to passive messaging

background/navigation-manager.js

@@ -66,6 +66,21 @@ bgReady.all.then(() => {
       {hostEquals: 'sleazyfork.org', urlMatches},
     ],
   });
+
+  /*
+   * Removes the Get Stylus button on style pages.
+   * Not using manifest.json as adding a content script disables the extension on update.
+   */
+  chrome.webNavigation.onCommitted.addListener(({tabId}) => {
+    chrome.tabs.executeScript(tabId, {
+      file: '/content/install-hook-userstylesworld.js',
+      runAt: 'document_start',
+    });
+  }, {
+    url: [
+      {hostEquals: 'userstyles.world', urlMatches: '/style/\\d+[^/]*/[a-z-0-9]+$'},
+    ],
+  });
   /*
    * FF misses some about:blank iframes so we inject our content script explicitly
    */

content/install-hook-userstylesworld.js

@@ -1,40 +1,16 @@
 'use strict';
 
 (() => {
-  function watchForStylusButton() {
+  const allowedOrigin = 'https://userstyles.world';
-    // Use 1 function so we won't have duplicate code around.
-    const stylusQuery = () => document.querySelector('a#stylus');
 
-    if (!stylusQuery()) {
+  const onPageLoaded = event => {
-      const stylusButtonObserver = new MutationObserver(() => {
+    if (event.data
-        if (stylusQuery()) {
+    && event.data.type === 'usw-remove-stylus-button'
-          stylusButtonObserver.disconnect();
+    && allowedOrigin === event.origin
-          stylusQuery().remove();
+    ) {
-        }
+      document.querySelector('a#stylus').remove();
-      });
-      stylusButtonObserver.observe(document.body, {childList: true, subtree: true});
-    } else {
-      stylusQuery().remove();
     }
-  }
+  };
-
-  // Some trickery to make sure that the DOM is ready(document.body/document.head).
-  // And can possibly observe it for a stylus button.
-
-  function isDOMReady() {
-    return document.readyState === 'complete' || document.readyState === 'interactive';
-  }
-
-  if (!isDOMReady()) {
-    const onReadyStateChange = () => {
-      if (isDOMReady()) {
-        document.removeEventListener('readystatechange', onReadyStateChange);
-        watchForStylusButton();
-      }
-    };
-    document.addEventListener('readystatechange', onReadyStateChange);
-  } else {
-    watchForStylusButton();
-  }
 
+  window.addEventListener('message', onPageLoaded);
 })();

manifest.json

@@ -89,12 +89,6 @@
       "run_at": "document_start",
       "all_frames": false,
       "js": ["content/install-hook-openusercss.js"]
-    },
-    {
-      "matches": ["https://userstyles.world/style/*"],
-      "run_at": "document_start",
-      "all_frames": false,
-      "js": ["content/install-hook-userstylesworld.js"]
     }
   ],
   "browser_action": {