Improve style caching, cache requests too, add code:false mode

Previously, when a cache was invalidated and every tab/iframe issued a getStyles request, we previous needlessly accessed IndexedDB for each of these requests. It happened because 1) the global cachedStyles was created only at the end of the async DB-reading, 2) and each style record is retrieved asynchronously so the single threaded JS engine interleaved all these operations. It could easily span a few seconds when many tabs are open and you have like 100 styles.

Now, in getStyles: all requests issued while cachedStyles is being populated are queued and invoked at the end.

Now, in filterStyles: all requests are cached using the request's options combined in a string as a key. It also helps on each navigation because we monitor page loading process at different stages: before, when committed, history traversal, requesting applicable styles by a content script. Icon badge update also may issue a copy of the just issued request by one of the navigation listeners.

Now, the caches are invalidated smartly: style add/update/delete/toggle only purges filtering cache, and modifies style cache in-place without re-reading the entire IndexedDB.

Now, code:false mode for manage page that only needs style meta. It reduces the transferred message size 10-100 times thus reducing the overhead caused by to internal JSON-fication in the extensions API.

Also fast&direct getStylesSafe for own pages; code cosmetics

.eslintrc

@@ -12,6 +12,7 @@ env:
 globals:
   CodeMirror: false
   runTryCatch: true
+  getStylesSafe: true
   getStyles: true
   updateIcon: true
   saveStyle: true

apply.js

@@ -9,20 +9,22 @@ var retiredStyleIds = [];
 initObserver();
 requestStyles();
 
-function requestStyles() {
+function requestStyles(options = {}) {
 	// If this is a Stylish page (Edit Style or Manage Styles),
 	// we'll request the styles directly to minimize delay and flicker,
 	// unless Chrome still starts up and the background page isn't fully loaded.
 	// (Note: in this case the function may be invoked again from applyStyles.)
-	var request = {method: "getStyles", matchUrl: location.href, enabled: true, asHash: true};
+	var request = Object.assign({
-	if (location.href.indexOf(chrome.extension.getURL("")) == 0) {
+		method: "getStyles",
-		var bg = chrome.extension.getBackgroundPage();
+		matchUrl: location.href,
-		if (bg && bg.getStyles) {
+		enabled: true,
-			// apply styles immediately, then proceed with a normal request that will update the icon
+		asHash: true,
-			bg.getStyles(request, applyStyles);
+	}, options);
-		}
+	if (typeof getStylesSafe !== 'undefined') {
-	}
+		getStylesSafe(request).then(applyStyles);
+	} else {
 		chrome.runtime.sendMessage(request, applyStyles);
+	}
 }
 
 chrome.runtime.onMessage.addListener(applyOnMessage);
@@ -34,6 +36,10 @@ function applyOnMessage(request, sender, sendResponse) {
 			removeStyle(request.id, document);
 			break;
 		case "styleUpdated":
+			if (request.codeIsUpdated === false) {
+				applyStyleState(request.style.id, request.style.enabled, document);
+				break;
+			}
 			if (request.style.enabled) {
 				retireStyle(request.style.id);
 				// fallthrough to "styleAdded"
@@ -92,6 +98,20 @@ function disableAll(disable) {
 	}
 }
 
+function applyStyleState(id, enabled, doc) {
+	var e = doc.getElementById("stylus-" + id);
+	if (!e) {
+		if (enabled) {
+			requestStyles({id});
+		}
+	} else {
+		e.sheet.disabled = !enabled;
+		getDynamicIFrames(doc).forEach(function(iframe) {
+			applyStyleState(id, iframe.contentDocument);
+		});
+	}
+}
+
 function removeStyle(id, doc) {
 	var e = doc.getElementById("stylus-" + id);
 	delete g_styleElements["stylus-" + id];

background.js

@@ -1,36 +1,21 @@
 /* globals wildcardAsRegExp, KEEP_CHANNEL_OPEN */
 
-var frameIdMessageable;
-runTryCatch(function() {
-	chrome.tabs.sendMessage(0, {}, {frameId: 0}, function() {
-		var clearError = chrome.runtime.lastError;
-		frameIdMessageable = true;
-	});
-});
-
 // This happens right away, sometimes so fast that the content script isn't even ready. That's
 // why the content script also asks for this stuff.
-chrome.webNavigation.onCommitted.addListener(webNavigationListener.bind(this, "styleApply"));
+chrome.webNavigation.onCommitted.addListener(webNavigationListener.bind(this, 'styleApply'));
-// Not supported in Firefox - https://bugzilla.mozilla.org/show_bug.cgi?id=1239349
+chrome.webNavigation.onHistoryStateUpdated.addListener(webNavigationListener.bind(this, 'styleReplaceAll'));
-if ("onHistoryStateUpdated" in chrome.webNavigation) {
-	chrome.webNavigation.onHistoryStateUpdated.addListener(webNavigationListener.bind(this, "styleReplaceAll"));
-}
 chrome.webNavigation.onBeforeNavigate.addListener(webNavigationListener.bind(this, null));
+
 function webNavigationListener(method, data) {
-	// Until Chrome 41, we can't target a frame with a message
+	getStyles({matchUrl: data.url, enabled: true, asHash: true}, styles => {
-	// (https://developer.chrome.com/extensions/tabs#method-sendMessage)
+		// we can't inject chrome:// and chrome-extension:// pages except our own
-	// so a style affecting a page with an iframe will affect the main page as well.
+		// that request the styles on their own, so we'll only update the icon
-	// Skip doing this for frames in pre-41 to prevent page flicker.
+		if (method && !data.url.startsWith('chrome')) {
-	if (data.frameId != 0 && !frameIdMessageable) {
+			chrome.tabs.sendMessage(data.tabId, {method, styles}, {frameId: data.frameId});
-		return;
-	}
-	getStyles({matchUrl: data.url, enabled: true, asHash: true}, function(styleHash) {
-		if (method) {
-			chrome.tabs.sendMessage(data.tabId, {method: method, styles: styleHash},
-				frameIdMessageable ? {frameId: data.frameId} : undefined);
 		}
+		// main page frame id is 0
 		if (data.frameId == 0) {
-			updateIcon({id: data.tabId, url: data.url}, styleHash);
+			updateIcon({id: data.tabId, url: data.url}, styles);
 		}
 	});
 }
@@ -70,7 +55,7 @@ chrome.runtime.onMessage.addListener(function(request, sender, sendResponse) {
 			return KEEP_CHANNEL_OPEN;
 		case "invalidateCache":
 			if (typeof invalidateCache != "undefined") {
-				invalidateCache(false);
+				invalidateCache(false, request);
 			}
 			break;
 		case "healthCheck":

edit.js

@@ -1087,18 +1087,10 @@ function init() {
 	}
 	// This is an edit
 	tE("heading", "editStyleHeading", null, false);
-	requestStyle();
+	getStylesSafe({id: params.id}).then(styles => {
-	function requestStyle() {
+		styleId = styles[0].id;
-		chrome.runtime.sendMessage({method: "getStyles", id: params.id}, function callback(styles) {
+		initWithStyle(styles[0]);
-			if (!styles) { // Chrome is starting up and shows edit.html
-				requestStyle();
-				return;
-			}
-			var style = styles[0];
-			styleId = style.id;
-			initWithStyle(style);
 	});
-	}
 }
 
 function initWithStyle(style) {
@@ -1107,7 +1099,7 @@ function initWithStyle(style) {
 	document.getElementById("url").href = style.url;
 	// if this was done in response to an update, we need to clear existing sections
 	getSections().forEach(function(div) { div.remove(); });
-	var queue = style.sections.length ? style.sections : [{code: ""}];
+	var queue = style.sections.length ? style.sections.slice() : [{code: ""}];
 	var queueStart = new Date().getTime();
 	// after 100ms the sections will be added asynchronously
 	while (new Date().getTime() - queueStart <= 100 && queue.length) {

manage.js

@@ -6,13 +6,9 @@ var appliesToExtraTemplate = document.createElement("span");
 appliesToExtraTemplate.className = "applies-to-extra";
 appliesToExtraTemplate.innerHTML = " " + t('appliesDisplayTruncatedSuffix');
 
-chrome.runtime.sendMessage({method: "getStyles"}, showStyles);
+getStylesSafe({code: false}).then(showStyles);
 
 function showStyles(styles) {
-	if (!styles) { // Chrome is starting up
-		chrome.runtime.sendMessage({method: "getStyles"}, showStyles);
-		return;
-	}
 	if (!installed) {
 		// "getStyles" message callback is invoked before document is loaded,
 		// postpone the action until DOMContentLoaded is fired

messaging.js

@@ -4,13 +4,16 @@ const OWN_ORIGIN = chrome.runtime.getURL('');
 
 function notifyAllTabs(request) {
 	// list all tabs including chrome-extension:// which can be ours
+	if (request.codeIsUpdated === false && request.style) {
+		request = Object.assign({}, request, {
+			style: getStyleWithNoCode(request.style)
+    });
+	}
 	chrome.tabs.query({}, tabs => {
 		for (let tab of tabs) {
-			if (request.codeIsUpdated !== false || tab.url.startsWith(OWN_ORIGIN)) {
 			chrome.tabs.sendMessage(tab.id, request);
 			updateIcon(tab);
 		}
-		}
 	});
 	// notify all open popups
 	const reqPopup = Object.assign({}, request, {method: 'updatePopup', reason: request.method});
@@ -47,57 +50,59 @@ function refreshAllTabs() {
 function updateIcon(tab, styles) {
 	// while NTP is still loading only process the request for its main frame with a real url
 	// (but when it's loaded we should process style toggle requests from popups, for example)
-	if (tab.url == "chrome://newtab/" && tab.status != "complete") {
+	if (tab.url == 'chrome://newtab/' && tab.status != 'complete') {
 		return;
 	}
 	if (styles) {
 		// check for not-yet-existing tabs e.g. omnibox instant search
-		chrome.tabs.get(tab.id, function() {
+		chrome.tabs.get(tab.id, () => {
 			if (!chrome.runtime.lastError) {
-				// for 'styles' asHash:true fake the length by counting numeric ids manually
-				if (styles.length === undefined) {
-					styles.length = 0;
-					for (var id in styles) {
-						styles.length += id.match(/^\d+$/) ? 1 : 0;
-					}
-				}
 				stylesReceived(styles);
 			}
 		});
 		return;
 	}
-	getTabRealURL(tab, function(url) {
+	getTabRealURL(tab, url => {
-		// if we have access to this, call directly. a page sending a message to itself doesn't seem to work right.
+		// if we have access to this, call directly
-		if (typeof getStyles != "undefined") {
+		// (Chrome no longer sends messages to the page itself)
-			getStyles({matchUrl: url, enabled: true}, stylesReceived);
+		const options = {method: 'getStyles', matchUrl: url, enabled: true, asHash: true};
+		if (typeof getStyles != 'undefined') {
+			getStyles(options, stylesReceived);
 		} else {
-			chrome.runtime.sendMessage({method: "getStyles", matchUrl: url, enabled: true}, stylesReceived);
+			chrome.runtime.sendMessage(options, stylesReceived);
 		}
 	});
 
 	function stylesReceived(styles) {
-		var disableAll = "disableAll" in styles ? styles.disableAll : prefs.get("disableAll");
+		let numStyles = styles.length;
-		var postfix = disableAll ? "x" : styles.length == 0 ? "w" : "";
+		if (numStyles === undefined) {
+			// for 'styles' asHash:true fake the length by counting numeric ids manually
+			numStyles = 0;
+			for (let id of Object.keys(styles)) {
+				numStyles += id.match(/^\d+$/) ? 1 : 0;
+			}
+		}
+		const disableAll = 'disableAll' in styles ? styles.disableAll : prefs.get('disableAll');
+		const postfix = disableAll ? 'x' : numStyles == 0 ? 'w' : '';
 		chrome.browserAction.setIcon({
 			path: {
 				// Material Design 2016 new size is 16px
-				16: "16" + postfix + ".png", 32: "32" + postfix + ".png",
+				16: '16' + postfix + '.png', 32: '32' + postfix + '.png',
 				// Chromium forks or non-chromium browsers may still use the traditional 19px
-				19: "19" + postfix + ".png", 38: "38" + postfix + ".png",
+				19: '19' + postfix + '.png', 38: '38' + postfix + '.png',
 			},
 			tabId: tab.id
-		}, function() {
+		}, () => {
 			// if the tab was just closed an error may occur,
 			// e.g. 'windowPosition' pref updated in edit.js::window.onbeforeunload
 			if (!chrome.runtime.lastError) {
-				var t = prefs.get("show-badge") && styles.length ? ("" + styles.length) : "";
+				const text = prefs.get('show-badge') && numStyles ? String(numStyles) : '';
-				chrome.browserAction.setBadgeText({text: t, tabId: tab.id});
+				chrome.browserAction.setBadgeText({text, tabId: tab.id});
 				chrome.browserAction.setBadgeBackgroundColor({
 					color: prefs.get(disableAll ? 'badgeDisabled' : 'badgeNormal')
 				});
 			}
 		});
-		//console.log("Tab " + tab.id + " (" + tab.url + ") badge text set to '" + t + "'.");
 	}
 }
 

popup.js

@@ -19,7 +19,8 @@ function updatePopUp(url) {
 		return;
 	}
 
-	chrome.runtime.sendMessage({method: "getStyles", matchUrl: url}, showStyles);
+	getStylesSafe({matchUrl: url}).then(showStyles);
+
 	document.querySelector("#find-styles a").href = "https://userstyles.org/styles/browse/all/" + encodeURIComponent("file" === urlWillWork[1] ? "file:" : url);
 
 	// Write new style links

storage.js

@@ -17,103 +17,226 @@ function getDatabase(ready, error) {
 	}
 };
 
-var cachedStyles = null;
+
-function getStyles(options, callback) {
+// Let manage/popup/edit reuse background page variables
-	if (cachedStyles != null) {
+// Note, only "var"-declared variables are visible from another extension page
-		callback(filterStyles(cachedStyles, options));
+var cachedStyles = ((bg) => bg && bg.cache || {
+	bg,
+	list: null,
+	noCode: null,
+	byId: new Map(),
+	filters: new Map(),
+	mutex: {
+		inProgress: false,
+		onDone: [],
+	},
+})(chrome.extension.getBackgroundPage());
+
+
+// in case Chrome haven't yet loaded the bg page and displays our page like edit/manage
+function getStylesSafe(options) {
+	return new Promise(resolve => {
+		if (cachedStyles.bg) {
+			getStyles(options, resolve);
 			return;
 		}
-	getDatabase(function(db) {
+		chrome.runtime.sendMessage(Object.assign({method: 'getStyles'}, options), styles => {
-		var tx = db.transaction(["styles"], "readonly");
+			if (!styles) {
-		var os = tx.objectStore("styles");
+				resolve(getStylesSafe(options));
-		var all = [];
+			} else {
-		os.openCursor().onsuccess = function(event) {
+				cachedStyles = chrome.extension.getBackgroundPage().cachedStyles;
-			var cursor = event.target.result;
+				resolve(styles);
+			}
+		});
+	});
+}
+
+
+function getStyles(options, callback) {
+	if (cachedStyles.list) {
+		callback(filterStyles(options));
+		return;
+	}
+	if (cachedStyles.mutex.inProgress) {
+		cachedStyles.mutex.onDone.push({options, callback});
+		return;
+	}
+	cachedStyles.mutex.inProgress = true;
+
+	const t0 = performance.now()
+	getDatabase(db => {
+		const tx = db.transaction(['styles'], 'readonly');
+		const os = tx.objectStore('styles');
+		const all = [];
+		os.openCursor().onsuccess = event => {
+			const cursor = event.target.result;
 			if (cursor) {
-				var s = cursor.value;
+				const s = cursor.value;
 				s.id = cursor.key;
 				all.push(cursor.value);
 				cursor.continue();
 			} else {
-				cachedStyles = all;
+				cachedStyles.list = all;
+				cachedStyles.noCode = [];
+				for (let style of all) {
+					const noCode = getStyleWithNoCode(style);
+					cachedStyles.noCode.push(noCode);
+					cachedStyles.byId.set(style.id, {style, noCode});
+				}
+				//console.log('%s getStyles %s, invoking cached callbacks: %o', (performance.now() - t0).toFixed(1), JSON.stringify(options), cache.mutex.onDone.map(e => JSON.stringify(e.options)))
 				try{
-					callback(filterStyles(all, options));
+					callback(filterStyles(options));
 				} catch(e){
 					// no error in console, it works
 				}
+
+				cachedStyles.mutex.inProgress = false;
+				for (let {options, callback} of cachedStyles.mutex.onDone) {
+					callback(filterStyles(options));
+				}
+				cachedStyles.mutex.onDone = [];
 			}
 		};
 	}, null);
 }
 
-function invalidateCache(andNotify) {
+
-	cachedStyles = null;
+function getStyleWithNoCode(style) {
+	const stripped = Object.assign({}, style, {sections: []});
+	for (let section of style.sections) {
+		stripped.sections.push(Object.assign({}, section, {code: null}));
+	}
+	return stripped;
+}
+
+
+function invalidateCache(andNotify, {added, updated, deletedId} = {}) {
+	// prevent double-add on echoed invalidation
+	const cached = added && cachedStyles.byId.get(added.id);
+	if (cached) {
+		return;
+	}
 	if (andNotify) {
-		chrome.runtime.sendMessage({method: "invalidateCache"});
+		chrome.runtime.sendMessage({method: 'invalidateCache', added, updated, deletedId});
 	}
+	if (!cachedStyles.list) {
+		return;
+	}
+	if (updated) {
+		const cached = cachedStyles.byId.get(updated.id);
+		if (cached) {
+			Object.assign(cached.style, updated);
+			Object.assign(cached.noCode, getStyleWithNoCode(updated));
+			//console.log('cache: updated', updated);
+		}
+		cachedStyles.filters.clear();
+		return;
+	}
+	if (added) {
+		const noCode = getStyleWithNoCode(added);
+		cachedStyles.list.push(added);
+		cachedStyles.noCode.push(noCode);
+		cachedStyles.byId.set(added.id, {style: added, noCode});
+		//console.log('cache: added', added);
+		cachedStyles.filters.clear();
+		return;
+	}
+	if (deletedId != undefined) {
+		const deletedStyle = (cachedStyles.byId.get(deletedId) || {}).style;
+		if (deletedStyle) {
+			const cachedIndex = cachedStyles.list.indexOf(deletedStyle);
+			cachedStyles.list.splice(cachedIndex, 1);
+			cachedStyles.noCode.splice(cachedIndex, 1);
+			cachedStyles.byId.delete(deletedId);
+			//console.log('cache: deleted', deletedStyle);
+			cachedStyles.filters.clear();
+			return;
+		}
+	}
+	cachedStyles.list = null;
+	cachedStyles.noCode = null;
+	//console.log('cache cleared');
+	cachedStyles.filters.clear();
 }
 
-function filterStyles(styles, options) {
-	var enabled = fixBoolean(options.enabled);
-	var url = "url" in options ? options.url : null;
-	var id = "id" in options ? Number(options.id) : null;
-	var matchUrl = "matchUrl" in options ? options.matchUrl : null;
 
-	if (enabled != null) {
+function filterStyles(options = {}) {
-		styles = styles.filter(function(style) {
+	const t0 = performance.now()
-			return style.enabled == enabled;
+	const enabled = fixBoolean(options.enabled);
-		});
+	const url = 'url' in options ? options.url : null;
+	const id = 'id' in options ? Number(options.id) : null;
+	const matchUrl = 'matchUrl' in options ? options.matchUrl : null;
+	const code = 'code' in options ? options.code : true;
+	const asHash = 'asHash' in options ? options.asHash : false;
+
+	if (enabled == null
+		&& url == null
+		&& id == null
+		&& matchUrl == null
+		&& asHash != true) {
+		//console.log('%c%s filterStyles SKIPPED LOOP %s', 'color:gray', (performance.now() - t0).toFixed(1), JSON.stringify(options))
+		return code ? cachedStyles.list : cachedStyles.noCode;
 	}
-	if (url != null) {
+
-		styles = styles.filter(function(style) {
+	// add \t after url to prevent collisions (not sure it can actually happen though)
-			return style.url == url;
+	const cacheKey = '' + enabled + url + '\t' + id + matchUrl + '\t' + code + asHash;
-		});
+	const cached = cachedStyles.filters.get(cacheKey);
+	if (cached) {
+		//console.log('%c%s filterStyles REUSED RESPONSE %s', 'color:gray', (performance.now() - t0).toFixed(1), JSON.stringify(options))
+		return asHash
+			? Object.assign({disableAll: prefs.get('disableAll', false)}, cached)
+			: cached;
 	}
-	if (id != null) {
+
-		styles = styles.filter(function(style) {
+	const styles = id == null
-			return style.id == id;
+		? (code ? cachedStyles.list : cachedStyles.noCode)
-		});
+		: [code ? cachedStyles.byId.get(id).style : cachedStyles.byId.get(id).noCode];
-	}
+	const filtered = asHash ? {} : [];
-	if (matchUrl != null) {
+
-		// Return as a hash from style to applicable sections? Can only be used with matchUrl.
+	for (let i = 0, style; (style = styles[i]); i++) {
-		var asHash = "asHash" in options ? options.asHash : false;
+		if ((enabled == null || style.enabled == enabled)
+			&& (url == null || style.url == url)
+			&& (id == null || style.id == id)) {
+			const sections = (asHash || matchUrl != null) && getApplicableSections(style, matchUrl);
 			if (asHash) {
-			var h = {disableAll: prefs.get("disableAll", false)};
+				if (sections.length) {
-			styles.forEach(function(style) {
+					filtered[style.id] = sections;
-				var applicableSections = getApplicableSections(style, matchUrl);
-				if (applicableSections.length > 0) {
-					h[style.id] = applicableSections;
 				}
-			});
+			} else if (matchUrl == null || sections.length) {
-			return h;
+				filtered.push(style);
 			}
-		styles = styles.filter(function(style) {
-			var applicableSections = getApplicableSections(style, matchUrl);
-			return applicableSections.length > 0;
-		});
 		}
-	return styles;
+	}
+	//console.log('%s filterStyles %s', (performance.now() - t0).toFixed(1), JSON.stringify(options))
+	cachedStyles.filters.set(cacheKey, filtered);
+	return asHash
+		? Object.assign({disableAll: prefs.get('disableAll', false)}, filtered)
+		: filtered;
 }
 
+
 function saveStyle(style, {notify = true} = {}) {
 	return new Promise(resolve => {
 		getDatabase(db => {
 			const tx = db.transaction(['styles'], 'readwrite');
 			const os = tx.objectStore('styles');
 
+			delete style.method;
+
 			// Update
 			if (style.id) {
 				style.id = Number(style.id);
 				os.get(style.id).onsuccess = eventGet => {
 					const oldStyle = Object.assign({}, eventGet.target.result);
-					const codeIsUpdated = !styleSectionsEqual(style, oldStyle);
+					const codeIsUpdated = 'sections' in style && !styleSectionsEqual(style, oldStyle);
 					style = Object.assign(oldStyle, style);
+					addMissingStyleTargets(style);
 					os.put(style).onsuccess = eventPut => {
 						style.id = style.id || eventPut.target.result;
+						invalidateCache(notify, {updated: style});
 						if (notify) {
 							notifyAllTabs({method: 'styleUpdated', style, codeIsUpdated});
 						}
-						invalidateCache(notify);
 						resolve(style);
 					};
 				};
@@ -121,6 +244,7 @@ function saveStyle(style, {notify = true} = {}) {
 			}
 
 			// Create
+			delete style.id;
 			style = Object.assign({
 				// Set optional things if they're undefined
 				enabled: true,
@@ -128,23 +252,12 @@ function saveStyle(style, {notify = true} = {}) {
 				md5Url: null,
 				url: null,
 				originalMd5: null,
-			}, style, {
+			}, style);
-				// Set other optional things to empty array if they're undefined
+			addMissingStyleTargets(style);
-				sections: style.sections.map(section =>
-					Object.assign({
-						urls: [],
-						urlPrefixes: [],
-						domains: [],
-						regexps: [],
-					}, section)
-				),
-			})
-			// Make sure it's not null - that makes indexeddb sad
-			delete style.id;
 			os.add(style).onsuccess = event => {
-				invalidateCache(true);
 				// Give it the ID that was generated
 				style.id = event.target.result;
+				invalidateCache(true, {added: style});
 				notifyAllTabs({method: 'styleAdded', style});
 				resolve(style);
 			};
@@ -152,13 +265,25 @@ function saveStyle(style, {notify = true} = {}) {
 	});
 }
 
-function enableStyle(id, enabled) {
+
-	saveStyle({id: id, enabled: enabled}).then(style => {
+function addMissingStyleTargets(style) {
-		handleUpdate(style);
+	style.sections = (style.sections || []).map(section =>
-		notifyAllTabs({method: "styleUpdated", style});
+		Object.assign({
-	});
+			urls: [],
+			urlPrefixes: [],
+			domains: [],
+			regexps: [],
+		}, section)
+	);
 }
 
+
+function enableStyle(id, enabled) {
+	saveStyle({id, enabled})
+		.then(handleUpdate);
+}
+
+
 function deleteStyle(id, callback = function (){}) {
 	getDatabase(function(db) {
 		var tx = db.transaction(["styles"], "readwrite");
@@ -166,13 +291,14 @@ function deleteStyle(id, callback = function (){}) {
 		var request = os.delete(Number(id));
 		request.onsuccess = function(event) {
 			handleDelete(id);
-			invalidateCache(true);
+			invalidateCache(true, {deletedId: id});
-			notifyAllTabs({method: "styleDeleted", id: id});
+			notifyAllTabs({method: "styleDeleted", id});
 			callback();
 		};
 	});
 }
 
+
 function reportError() {
 	for (i in arguments) {
 		if ("message" in arguments[i]) {
@@ -182,6 +308,7 @@ function reportError() {
 	}
 }
 
+
 function fixBoolean(b) {
 	if (typeof b != "undefined") {
 		return b != "false";
@@ -189,6 +316,7 @@ function fixBoolean(b) {
 	return null;
 }
 
+
 function getDomains(url) {
 	if (url.indexOf("file:") == 0) {
 		return [];
@@ -202,6 +330,7 @@ function getDomains(url) {
 	return domains;
 }
 
+
 function getType(o) {
 	if (typeof o == "undefined" || typeof o == "string") {
 		return typeof o;
@@ -212,7 +341,8 @@ function getType(o) {
 	throw "Not supported - " + o;
 }
 
-var namespacePattern = /^\s*(@namespace[^;]+;\s*)+$/;
+const namespacePattern = /^\s*(@namespace[^;]+;\s*)+$/;
+
 function getApplicableSections(style, url) {
 	var sections = style.sections.filter(function(section) {
 		return sectionAppliesToUrl(section, url);
@@ -224,6 +354,7 @@ function getApplicableSections(style, url) {
 	return sections;
 }
 
+
 function sectionAppliesToUrl(section, url) {
 	// only http, https, file, and chrome-extension allowed
 	if (url.indexOf("http") != 0 && url.indexOf("file") != 0 && url.indexOf("chrome-extension") != 0 && url.indexOf("ftp") != 0) {
@@ -275,6 +406,7 @@ function sectionAppliesToUrl(section, url) {
 	return false;
 }
 
+
 function isCheckbox(el) {
 	return el.nodeName.toLowerCase() == "input" && "checkbox" == el.type.toLowerCase();
 }
@@ -462,6 +594,7 @@ var prefs = chrome.extension.getBackgroundPage().prefs || new function Prefs() {
 	}
 };
 
+
 function getCodeMirrorThemes(callback) {
 	chrome.runtime.getPackageDirectoryEntry(function(rootDir) {
 		rootDir.getDirectory("codemirror/theme", {create: false}, function(themeDir) {
@@ -481,6 +614,7 @@ function getCodeMirrorThemes(callback) {
 	});
 }
 
+
 function sessionStorageHash(name) {
 	var hash = {
 		value: {},
@@ -495,6 +629,7 @@ function sessionStorageHash(name) {
 	return hash;
 }
 
+
 function deepCopy(obj) {
 	if (!obj || typeof obj != "object") {
 		return obj;
@@ -504,6 +639,7 @@ function deepCopy(obj) {
 	}
 }
 
+
 function deepMerge(target, obj1 /* plus any number of object arguments */) {
 	for (var i = 1; i < arguments.length; i++) {
 		var obj = arguments[i];
@@ -522,6 +658,7 @@ function deepMerge(target, obj1 /* plus any number of object arguments */) {
 	return target;
 }
 
+
 function equal(a, b) {
 	if (!a || !b || typeof a != "object" || typeof b != "object") {
 		return a === b;
@@ -537,6 +674,7 @@ function equal(a, b) {
 	return true;
 }
 
+
 function defineReadonlyProperty(obj, key, value) {
 	var copy = deepCopy(value);
 	// In ES6, freezing a literal is OK (it returns the same value), but in previous versions it's an exception.
@@ -546,7 +684,7 @@ function defineReadonlyProperty(obj, key, value) {
 	Object.defineProperty(obj, key, {value: copy, configurable: true})
 }
 
-// Polyfill, can be removed when Firefox gets this - https://bugzilla.mozilla.org/show_bug.cgi?id=1220494
+// Polyfill for Firefox < 53 https://bugzilla.mozilla.org/show_bug.cgi?id=1220494
 function getSync() {
 	if ("sync" in chrome.storage) {
 		return chrome.storage.sync;
@@ -567,6 +705,7 @@ function getSync() {
 	}
 }
 
+
 function styleSectionsEqual(styleA, styleB) {
 	if (!styleA.sections || !styleB.sections) {
 		return undefined;