tor-browser

PageStyleChild.sys.mjs (6008B)

---

/* This Source Code Form is subject to the terms of the Mozilla Public
* License, v. 2.0. If a copy of the MPL was not distributed with this
* file, You can obtain one at http://mozilla.org/MPL/2.0/. */

export class PageStyleChild extends JSWindowActorChild {
 actorCreated() {
   // C++ can create the actor and call us here once an "interesting" link
   // element gets added to the DOM. If pageload hasn't finished yet, just
   // wait for that by doing nothing; the actor registration event
   // listeners will ensure we get the pageshow event.
   // It is also possible we get created in response to the parent
   // sending us a message - in that case, it's still worth doing the
   // same things here:
   if (!this.browsingContext || !this.browsingContext.associatedWindow) {
     return;
   }
   let { document } = this.browsingContext.associatedWindow;
   if (document.readyState != "complete") {
     return;
   }
   // If we've already seen a pageshow, send stylesheets now:
   this.#collectAndSendSheets();
 }

 handleEvent(event) {
   if (event?.type != "pageshow") {
     throw new Error("Unexpected event!");
   }

   // On page show, tell the parent all of the stylesheets this document
   // has. If we are in the topmost browsing context, delete the stylesheets
   // from the previous page.
   if (this.browsingContext.top === this.browsingContext) {
     this.sendAsyncMessage("PageStyle:Clear");
   }

   this.#collectAndSendSheets();
 }

 receiveMessage(msg) {
   switch (msg.name) {
     // Sent when the page's enabled style sheet is changed.
     case "PageStyle:Switch":
       if (this.browsingContext.top == this.browsingContext) {
         this.browsingContext.authorStyleDisabledDefault = false;
       }
       this.docShell.docViewer.authorStyleDisabled = false;
       this._switchStylesheet(msg.data.title);
       break;
     // Sent when "No Style" is chosen.
     case "PageStyle:Disable":
       if (this.browsingContext.top == this.browsingContext) {
         this.browsingContext.authorStyleDisabledDefault = true;
       }
       this.docShell.docViewer.authorStyleDisabled = true;
       break;
   }
 }

 /**
  * Returns links that would represent stylesheets once loaded.
  */
 _collectLinks(document) {
   let result = [];
   for (let link of document.querySelectorAll("link")) {
     if (link.namespaceURI !== "http://www.w3.org/1999/xhtml") {
       continue;
     }
     let isStyleSheet = Array.from(link.relList).some(
       r => r.toLowerCase() == "stylesheet"
     );
     if (!isStyleSheet) {
       continue;
     }
     if (!link.href) {
       continue;
     }
     result.push(link);
   }
   return result;
 }

 /**
  * Switch the stylesheet so that only the sheet with the given title is enabled.
  */
 _switchStylesheet(title) {
   let document = this.document;
   let docStyleSheets = Array.from(document.styleSheets);
   let links;

   // Does this doc contain a stylesheet with this title?
   // If not, it's a subframe's stylesheet that's being changed,
   // so no need to disable stylesheets here.
   let docContainsStyleSheet = !title;
   if (title) {
     links = this._collectLinks(document);
     docContainsStyleSheet =
       docStyleSheets.some(sheet => sheet.title == title) ||
       links.some(link => link.title == title);
   }

   for (let sheet of docStyleSheets) {
     if (sheet.title) {
       if (docContainsStyleSheet) {
         sheet.disabled = sheet.title !== title;
       }
     } else if (sheet.disabled) {
       sheet.disabled = false;
     }
   }

   // If there's no title, we just need to disable potentially-enabled
   // stylesheets via document.styleSheets, so no need to deal with links
   // there.
   //
   // We don't want to enable <link rel="stylesheet" disabled> without title
   // that were not enabled before.
   if (title) {
     for (let link of links) {
       if (link.title == title && link.disabled) {
         link.disabled = false;
       }
     }
   }
 }

 #collectAndSendSheets() {
   let window = this.browsingContext.associatedWindow;
   window.requestIdleCallback(() => {
     if (!window || window.closed) {
       return;
     }
     let filteredStyleSheets = this.#collectStyleSheets(window);
     this.sendAsyncMessage("PageStyle:Add", {
       filteredStyleSheets,
       preferredStyleSheetSet: this.document.preferredStyleSheetSet,
     });
   });
 }

 /**
  * Get the stylesheets that have a title (and thus can be switched) in this
  * webpage.
  *
  * @param content     The window object for the page.
  */
 #collectStyleSheets(content) {
   let result = [];
   let document = content.document;

   for (let sheet of document.styleSheets) {
     let title = sheet.title;
     if (!title) {
       // Sheets without a title are not alternates.
       continue;
     }

     // Skip any stylesheets that don't match the screen media type.
     let media = sheet.media.mediaText;
     if (media && !content.matchMedia(media).matches) {
       continue;
     }

     // We skip links here, see below.
     if (
       sheet.href &&
       sheet.ownerNode &&
       sheet.ownerNode.nodeName.toLowerCase() == "link"
     ) {
       continue;
     }

     let disabled = sheet.disabled;
     result.push({ title, disabled });
   }

   // This is tricky, because we can't just rely on document.styleSheets, as
   // `<link disabled>` makes the sheet don't appear there at all.
   for (let link of this._collectLinks(document)) {
     let title = link.title;
     if (!title) {
       continue;
     }

     let media = link.media;
     if (media && !content.matchMedia(media).matches) {
       continue;
     }

     let disabled =
       link.disabled ||
       !!link.sheet?.disabled ||
       document.preferredStyleSheetSet != title;
     result.push({ title, disabled });
   }

   return result;
 }
}