Added black list and ask.

data/inject.js

@@ -1,12 +1,46 @@
-var getContext = unsafeWindow.HTMLCanvasElement.prototype.getContext
+var getContext = unsafeWindow.HTMLCanvasElement.prototype.getContext;
+var askFunctionName = Math.random().toString(16);
 
 function block(){
+	// consoe.log("block");
+	delete unsafeWindow.HTMLCanvasElement.prototype[askFunctionName];
 	unsafeWindow.HTMLCanvasElement.prototype.getContext = null;
 }
+function ask(){
+	// console.log("ask");
+	
+	Object.defineProperty(
+		unsafeWindow.HTMLCanvasElement.prototype,
+		askFunctionName,
+		{
+			value: getContext,
+			enumerabe: false
+		}
+	);
+	unsafeWindow.HTMLCanvasElement.prototype.getContext = new unsafeWindow.Function(function(){
+		var oldBorder = this.style.border;
+		this.style.border = "2px dashed red";
+		var confirmText =
+			this.parentNode?
+			"Do you want to allow the red bordered <canvas>?":
+			"Do you want to allow an invisibe <canvas>?";
+		var allow = confirm(confirmText);
+		this.style.border = oldBorder;
+		if (allow){
+			return this["askFunctionName"].apply(this, arguments);
+		}
+		else {
+			return null;
+		}
+	}.toString().replace(/^function\s*\(\)\s*\{|\}\s*$/g, "").replace("askFunctionName", askFunctionName));
+}
 function unblock(){
+	// console.log("unblock");
 	unsafeWindow.HTMLCanvasElement.prototype.getContext = getContext;
 }
 
+ask();
 self.port.on("block", block);
+self.port.on("ask", ask);
 self.port.on("unblock", unblock);
 self.port.on("detach", unblock);

lib/main.js

@@ -1,18 +1,44 @@
+function getDomainRegExpList(domainList){
+	return domainList
+		.split(",")
+		.map(function(entry){
+			return entry.replace(/^\s+|\s+$/g, "");
+		})
+		.filter(function(entry){
+			return !!entry.length;
+		})
+		.map(function(entry){
+			return new RegExp("(?:^|\\.)" + entry.replace(/([\\\+\*\?\[\^\]\$\(\)\{\}\=\!\|\.])/g, "\\$1") + "\\.?$", "i");
+		});
+}
+
 var self = require("sdk/self");
 var pageMod = require("sdk/page-mod");
 var preferences = require("sdk/simple-prefs");
 var prefs = preferences.prefs;
 var {URL} = require("sdk/url");
-var workers = [];
+
 var whiteList;
-updateWhiteList();
-
 function updateWhiteList(){
-	whiteList = prefs.whiteList.split(",").map(function(entry){
-		return new RegExp("(?:^|\\.)" + entry.replace(/([\\\+\*\?\[\^\]\$\(\)\{\}\=\!\|\.])/g, "\\$1") + "\\.?$", "i");
-	});
+	whiteList = getDomainRegExpList(prefs.whiteList);
 }
+updateWhiteList();
+preferences.on("whiteList", function(){
+	updateWhiteList();
+	workers.forEach(checkWorker);
+});
 
+var blackList;
+function updateBlackList(){
+	blackList = getDomainRegExpList(prefs.blackList);
+}
+updateBlackList();
+preferences.on("blackList", function(){
+	updateBackList();
+	workers.forEach(checkWorker);
+});
+
+var workers = [];
 function detachWorker(worker, workerArray) {
 	var index = workerArray.indexOf(worker);
 	if (index != -1){
@@ -20,22 +46,46 @@ function detachWorker(worker, workerArray) {
 	}
 }
 function checkWorker(worker){
-	var url = new URL(worker.url);
-	if (prefs.blockAll || !whiteList.some(function(entry){
-		return url.hostname.match(entry);
-	})){
+	if (prefs.blockAll){
 		worker.port.emit("block");
 	}
 	else {
+		var url = new URL(worker.url);
+		var inBlackList = blackList.some(function(entry){
+			return url.hostname.match(entry);
+		});
+		if (inBlackList){
+			worker.port.emit("block");
+		}
+		else {
+			var inWhiteList = whiteList.some(function(entry){
+				return url.hostname.match(entry);
+			});
+			if (inWhiteList){
 				worker.port.emit("unblock");
 			}
+			else {
+				if (prefs.askPermission){
+					worker.port.emit("ask");
+				}
+				else {
+					worker.port.emit("block");
+				}
+			}
+		}
+	}
 }
 
-preferences.on("whiteList", function(){
-	updateWhiteList();
+preferences.on("blockAll", function(){
+	if (prefs.blockAll){
+		prefs.askPermission = false;
+	}
 	workers.forEach(checkWorker);
 });
-preferences.on("blockAll", function(){
+preferences.on("askPermission", function(){
+	if (prefs.askPermission){
+		prefs.blockAll = false;
+	}
 	workers.forEach(checkWorker);
 });
 

package.json

@@ -17,6 +17,20 @@
 			"description": "If you want to block everything (ignore the white list).",
 			"type": "bool",
 			"value": false
+		},
+		{
+			"name": "blackList",
+			"title": "Black list",
+			"description": "Domains where the <canvas>-API should always be blocked. To add multiple domains seperate them by comma.",
+			"type": "string",
+			"value": ""
+		},
+		{
+			"name": "askPermission",
+			"title": "Ask for permission",
+			"description": "If you want to be asked if you want to block a canvas element if the domain is neither in the white or black list.",
+			"type": "bool",
+			"value": true
 		}
 	],
 	"author": "Korbinian Kapsner",