Blocking large media elements also prevents autoplay, regardless of size

Related issue:
https://github.com/uBlockOrigin/uBlock-issues/issues/3394

When the "No large media elements" per-site switch is toggled on,
it will also act to prevent autoplay of video/audio media, regardless
of their size. This also works for xhr-based media streaming.

If blocking by size is not desirable while blocking autoplay is
desired, one can toggle on "No large media elements" switch while
setting "Block media elements larger than ..." to a very high value.

platform/chromium/vapi-background-ext.js

@@ -19,10 +19,6 @@
     Home: https://github.com/gorhill/uBlock
 */
 
-/* globals browser */
-
-'use strict';
-
 /******************************************************************************/
 
 // https://github.com/uBlockOrigin/uBlock-issues/issues/1659
@@ -90,71 +86,47 @@ vAPI.Tabs = class extends vAPI.Tabs {
         ['gif','image'],['ico','image'],['jpeg','image'],['jpg','image'],['png','image'],['webp','image']
     ]);
 
-    const headerValue = (headers, name) => {
-        let i = headers.length;
-        while ( i-- ) {
-            if ( headers[i].name.toLowerCase() === name ) {
-                return headers[i].value.trim();
-            }
-        }
-        return '';
-    };
-
     const parsedURL = new URL('https://www.example.org/');
 
-    // Extend base class to normalize as per platform.
+    // Extend base class to normalize as per platform
 
     vAPI.Net = class extends vAPI.Net {
         normalizeDetails(details) {
             // Chromium 63+ supports the `initiator` property, which contains
-            // the URL of the origin from which the network request was made.
+            // the URL of the origin from which the network request was made
-            if (
+            if ( details.initiator && details.initiator !== 'null' ) {
-                typeof details.initiator === 'string' &&
-                details.initiator !== 'null'
-            ) {
                 details.documentUrl = details.initiator;
             }
-
+            const type = details.type;
-            let type = details.type;
-
             if ( type === 'imageset' ) {
                 details.type = 'image';
                 return;
             }
-
-            // The rest of the function code is to normalize type
             if ( type !== 'other' ) { return; }
-
+            // Try to map known "extension" part of URL to request type
-            // Try to map known "extension" part of URL to request type.
+            if ( details.responseHeaders === undefined ) {
                 parsedURL.href = details.url;
-            const path = parsedURL.pathname,
+                const path = parsedURL.pathname;
-                  pos = path.indexOf('.', path.length - 6);
+                const pos = path.indexOf('.', path.length - 6);
-            if ( pos !== -1 && (type = extToTypeMap.get(path.slice(pos + 1))) ) {
+                if ( pos !== -1 ) {
-                details.type = type;
+                    details.type = extToTypeMap.get(path.slice(pos + 1)) || type;
+                }
                 return;
             }
-
+            // Try to extract type from response headers
-            // Try to extract type from response headers if present.
+            const ctype = this.headerValue(details.responseHeaders, 'content-type');
-            if ( details.responseHeaders ) {
+            if ( ctype.startsWith('font/') ) {
-                type = headerValue(details.responseHeaders, 'content-type');
-                if ( type.startsWith('font/') ) {
                 details.type = 'font';
-                    return;
+            } else if ( ctype.startsWith('image/') ) {
-                }
-                if ( type.startsWith('image/') ) {
                 details.type = 'image';
-                    return;
+            } else if ( ctype.startsWith('audio/') || ctype.startsWith('video/') ) {
-                }
-                if ( type.startsWith('audio/') || type.startsWith('video/') ) {
                 details.type = 'media';
-                    return;
-                }
             }
         }
 
         // https://www.reddit.com/r/uBlockOrigin/comments/9vcrk3/
         //   Some types can be mapped from 'other', thus include 'other' if and
-        //   only if the caller is interested in at least one of those types.
+        //   only if the caller is interested in at least one of those types
         denormalizeTypes(types) {
             if ( types.length === 0 ) {
                 return Array.from(this.validTypes);

platform/common/vapi-background.js

@@ -1382,6 +1382,14 @@ vAPI.Net = class {
         if ( this.suspendDepth !== 0 ) { return; }
         this.unsuspendAllRequests(discard);
     }
+    headerValue(headers, name) {
+        for ( const header of headers ) {
+            if ( header.name.toLowerCase() === name ) {
+                return header.value.trim();
+            }
+        }
+        return '';
+    }
     static canSuspend() {
         return false;
     }

platform/firefox/vapi-background-ext.js

@@ -110,19 +110,16 @@ vAPI.Net = class extends vAPI.Net {
             details.type = 'image';
             return;
         }
+        if ( type !== 'object' ) { return; }
+        // Try to extract type from response headers if present.
+        if ( details.responseHeaders === undefined ) { return; }
+        const ctype = this.headerValue(details.responseHeaders, 'content-type');
         // https://github.com/uBlockOrigin/uBlock-issues/issues/345
         //   Re-categorize an embedded object as a `sub_frame` if its
         //   content type is that of a HTML document.
-        if ( type === 'object' && Array.isArray(details.responseHeaders) ) {
+        if ( ctype === 'text/html' ) {
-            for ( const header of details.responseHeaders ) {
-                if ( header.name.toLowerCase() === 'content-type' ) {
-                    if ( header.value.startsWith('text/html') ) {
             details.type = 'sub_frame';
         }
-                    break;
-                }
-            }
-        }
     }
 
     denormalizeTypes(types) {

src/js/pagestore.js

@@ -1019,10 +1019,29 @@ const PageStore = class {
     }
 
     // The caller is responsible to check whether filtering is enabled or not.
-    filterLargeMediaElement(fctxt, size) {
+    filterLargeMediaElement(fctxt, headers) {
         fctxt.filter = undefined;
-
+        if ( this.allowLargeMediaElementsUntil === 0 ) { return 0; }
-        if ( this.allowLargeMediaElementsUntil === 0 ) {
+        if ( sessionSwitches.evaluateZ('no-large-media', fctxt.getTabHostname() ) !== true ) {
+            this.allowLargeMediaElementsUntil = 0;
+            return 0;
+        }
+        // XHR-based streaming is never blocked but we want to prevent autoplay
+        if ( fctxt.itype === fctxt.XMLHTTPREQUEST ) {
+            const ctype = headers.contentType;
+            if ( ctype.startsWith('audio/') || ctype.startsWith('video/') ) {
+                this.largeMediaTimer.on(500);
+            }
+            return 0;
+        }
+        if ( Date.now() < this.allowLargeMediaElementsUntil ) {
+            if ( fctxt.itype === fctxt.MEDIA ) {
+                const sources = this.allowLargeMediaElementsRegex instanceof RegExp
+                    ? [ this.allowLargeMediaElementsRegex.source ]
+                    : [];
+                sources.push('^' + µb.escapeRegex(fctxt.url));
+                this.allowLargeMediaElementsRegex = new RegExp(sources.join('|'));
+            }
             return 0;
         }
         // Disregard large media elements previously allowed: for example, to
@@ -1033,34 +1052,18 @@ const PageStore = class {
         ) {
             return 0;
         }
-        if ( Date.now() < this.allowLargeMediaElementsUntil ) {
+        // Regardless of whether a media is blocked, we want to prevent autoplay
-            const sources = this.allowLargeMediaElementsRegex instanceof RegExp
+        if ( fctxt.itype === fctxt.MEDIA ) {
-                ? [ this.allowLargeMediaElementsRegex.source ]
+            this.largeMediaTimer.on(500);
-                : [];
-            sources.push('^' + µb.escapeRegex(fctxt.url));
-            this.allowLargeMediaElementsRegex = new RegExp(sources.join('|'));
-            return 0;
         }
-        if (
+        const size = headers.contentLength;
-            sessionSwitches.evaluateZ(
+        if ( isNaN(size) ) { return 0; }
-                'no-large-media',
+        if ( (size >>> 10) < µb.userSettings.largeMediaSize ) { return 0; }
-                fctxt.getTabHostname()
-            ) !== true
-        ) {
-            this.allowLargeMediaElementsUntil = 0;
-            return 0;
-        }
-        if ( (size >>> 10) < µb.userSettings.largeMediaSize ) {
-            return 0;
-        }
-
         this.largeMediaCount += 1;
         this.largeMediaTimer.on(500);
-
         if ( logger.enabled ) {
             fctxt.filter = sessionSwitches.toLogData();
         }
-
         return 1;
     }
 

src/js/scriptlets/load-large-media-interactive.js

@@ -28,8 +28,6 @@ if ( typeof vAPI !== 'object' || vAPI.loadAllLargeMedia instanceof Function ) {
     return;
 }
 
-/******************************************************************************/
-
 const largeMediaElementAttribute = 'data-' + vAPI.sessionId;
 const largeMediaElementSelector =
     ':root   audio[' + largeMediaElementAttribute + '],\n' +
@@ -37,25 +35,19 @@ const largeMediaElementSelector =
     ':root picture[' + largeMediaElementAttribute + '],\n' +
     ':root   video[' + largeMediaElementAttribute + ']';
 
-/******************************************************************************/
+const isMediaElement = elem =>
+    (/^(?:audio|img|picture|video)$/.test(elem.localName));
 
-const isMediaElement = function(elem) {
+const isPlayableMediaElement = elem =>
-    return /^(?:audio|img|picture|video)$/.test(elem.localName);
+    (/^(?:audio|video)$/.test(elem.localName));
-};
 
 /******************************************************************************/
 
 const mediaNotLoaded = function(elem) {
     switch ( elem.localName ) {
     case 'audio':
-    case 'video': {
+    case 'video':
-        const src = elem.src || '';
-        if ( src.startsWith('blob:') ) {
-            elem.autoplay = false;
-            elem.pause();
-        }
         return elem.readyState === 0 || elem.error !== null;
-    }
     case 'img': {
         if ( elem.naturalWidth !== 0 || elem.naturalHeight !== 0 ) {
             break;
@@ -99,10 +91,9 @@ const surveyMissingMediaElements = function() {
     return largeMediaElementCount;
 };
 
-if ( surveyMissingMediaElements() === 0 ) { return; }
+if ( surveyMissingMediaElements() ) {
-
+    // Insert CSS to highlight blocked media elements.
-// Insert CSS to highlight blocked media elements.
+    if ( vAPI.largeMediaElementStyleSheet === undefined ) {
-if ( vAPI.largeMediaElementStyleSheet === undefined ) {
         vAPI.largeMediaElementStyleSheet = [
             largeMediaElementSelector + ' {',
                 'border: 2px dotted red !important;',
@@ -122,6 +113,7 @@ if ( vAPI.largeMediaElementStyleSheet === undefined ) {
         ].join('\n');
         vAPI.userStylesheet.add(vAPI.largeMediaElementStyleSheet);
         vAPI.userStylesheet.apply();
+    }
 }
 
 /******************************************************************************/
@@ -258,6 +250,27 @@ document.addEventListener('error', onLoadError, true);
 
 /******************************************************************************/
 
+const autoPausedMedia = new WeakMap();
+
+for ( const elem of document.querySelectorAll('audio,video') ) {
+    elem.setAttribute('autoplay', 'false');
+}
+
+const preventAutoplay = function(ev) {
+    const elem = ev.target;
+    if ( isPlayableMediaElement(elem) === false ) { return; }
+    const currentSrc = elem.getAttribute('src') || '';
+    const pausedSrc = autoPausedMedia.get(elem);
+    if ( pausedSrc === currentSrc ) { return; }
+    autoPausedMedia.set(elem, currentSrc);
+    elem.setAttribute('autoplay', 'false');
+    elem.pause();
+};
+
+document.addEventListener('timeupdate', preventAutoplay, true);
+
+/******************************************************************************/
+
 vAPI.loadAllLargeMedia = function() {
     document.removeEventListener('click', onMouseClick, true);
     document.removeEventListener('loadeddata', onLoadedData, true);

src/js/traffic.js

@@ -488,7 +488,7 @@ const onHeadersReceived = function(details) {
     }
     if ( pageStore.getNetFilteringSwitch(fctxt) === false ) { return; }
 
-    if ( fctxt.itype === fctxt.IMAGE || fctxt.itype === fctxt.MEDIA ) {
+    if ( (fctxt.itype & foilLargeMediaElement.TYPE_BITS) !== 0 ) {
         const result = foilLargeMediaElement(details, fctxt, pageStore);
         if ( result !== undefined ) { return result; }
     }
@@ -1124,15 +1124,12 @@ const injectPP = function(fctxt, pageStore, responseHeaders) {
 const foilLargeMediaElement = function(details, fctxt, pageStore) {
     if ( details.fromCache === true ) { return; }
 
-    let size = 0;
+    onDemandHeaders.setHeaders(details.responseHeaders);
-    if ( µb.userSettings.largeMediaSize !== 0 ) {
+
-        const headers = details.responseHeaders;
+    const result = pageStore.filterLargeMediaElement(fctxt, onDemandHeaders);
-        const i = headerIndexFromName('content-length', headers);
+
-        if ( i === -1 ) { return; }
+    onDemandHeaders.reset();
-        size = parseInt(headers[i].value, 10) || 0;
-    }
 
-    const result = pageStore.filterLargeMediaElement(fctxt, size);
     if ( result === 0 ) { return; }
 
     if ( logger.enabled ) {
@@ -1142,16 +1139,15 @@ const foilLargeMediaElement = function(details, fctxt, pageStore) {
     return { cancel: true };
 };
 
+foilLargeMediaElement.TYPE_BITS = fc.IMAGE | fc.MEDIA | fc.XMLHTTPREQUEST;
+
 /******************************************************************************/
 
 // Caller must ensure headerName is normalized to lower case.
 
 const headerIndexFromName = function(headerName, headers) {
-    let i = headers.length;
+    for ( let i = 0, n = headers.length; i < n; i++ ) {
-    while ( i-- ) {
+        if ( headers[i].name.toLowerCase() === headerName ) { return i; }
-        if ( headers[i].name.toLowerCase() === headerName ) {
-            return i;
-        }
     }
     return -1;
 };
@@ -1161,6 +1157,24 @@ const headerValueFromName = function(headerName, headers) {
     return i !== -1 ? headers[i].value : '';
 };
 
+const onDemandHeaders = {
+    headers: [],
+    get contentLength() {
+        const contentLength = headerValueFromName('content-length', this.headers);
+        if ( contentLength === '' ) { return Number.NaN; }
+        return parseInt(contentLength, 10) || 0;
+    },
+    get contentType() {
+        return headerValueFromName('content-type', this.headers);
+    },
+    setHeaders(headers) {
+        this.headers = headers;
+    },
+    reset() {
+        this.headers = [];
+    }
+};
+
 /******************************************************************************/
 
 const strictBlockBypasser = {