Auto white-out with a finger when using apple stylus (#167)

When using an iPad with an apple stylus, finger touches now trigger the whiteout tool.
This behavior can be disabled by setting the environment variable AUTO_FINGER_WHITEOUT=disabled

* Auto white-out with a finger when using stylus

* Add AUTO_FINGER_WHITEOUT config variable

* Use local variable to remember if stylus was used and make behavior configurable

* Delete "stylus" property

* Make AUTO_FINGER_WHITEOUT on by default

Co-authored-by: Ophir LOJKINE <pere.jobs@gmail.com>

* Delete parseBool, add note about iPad/Pencil

Co-authored-by: ishabalin <ishabalin@apple.com>
Co-authored-by: Ophir LOJKINE <pere.jobs@gmail.com>

client-data/tools/pencil/pencil.js

 	// than this?
 	var MIN_PENCIL_INTERVAL_MS = Tools.server_config.MAX_EMIT_COUNT_PERIOD / Tools.server_config.MAX_EMIT_COUNT;
 
+	var AUTO_FINGER_WHITEOUT = Tools.server_config.AUTO_FINGER_WHITEOUT;
+	var hasUsedStylus = false;
+
 	//Indicates the id of the line the user is currently drawing or an empty string while the user is not drawing
 	var curLineId = "",
 		lastTime = performance.now(); //The time at which the last point was drawn
 		this.y = y;
 	}
 
+	function handleAutoWhiteOut(evt) {
+		if (evt.touches && evt.touches[0] && evt.touches[0].touchType == "stylus") {
+			//When using stylus, switch back to the primary
+			if (hasUsedStylus && Tools.curTool.secondary.active) {
+				Tools.change("Pencil");
+			}
+			//Remember if starting a line with a stylus
+			hasUsedStylus = true;
+		}
+		if (evt.touches && evt.touches[0] && evt.touches[0].touchType == "direct") {
+			//When used stylus and touched with a finger, switch to secondary
+			if (hasUsedStylus && !Tools.curTool.secondary.active) {
+				Tools.change("Pencil");
+			}
+		}
+	}
+
 	function startLine(x, y, evt) {
 
 		//Prevent the press from being interpreted by the browser
 		evt.preventDefault();
 
+		if (AUTO_FINGER_WHITEOUT) handleAutoWhiteOut(evt);
+
 		curLineId = Tools.generateUID("l"); //"l" for line
 
 		Tools.drawAndSend({
 			"release": stopLineAt,
 		},
 		"draw": draw,
+		"onstart": function(oldTool) {
+			//Reset stylus
+			hasUsedStylus = false;
+		},
 		"secondary": {
 			"name": "White-out",
 			"icon": "tools/pencil/whiteout_tape.svg",

server/client_configuration.js

   MAX_EMIT_COUNT: config.MAX_EMIT_COUNT,
   MAX_EMIT_COUNT_PERIOD: config.MAX_EMIT_COUNT_PERIOD,
   BLOCKED_TOOLS: config.BLOCKED_TOOLS,
+  AUTO_FINGER_WHITEOUT: config.AUTO_FINGER_WHITEOUT,
 };

server/configuration.js

 
   /** Blocked Tools. A comma-separated list of tools that should not appear on boards. */
   BLOCKED_TOOLS: (process.env["WBO_BLOCKED_TOOLS"] || "").split(","),
+
+  /** Automatically switch to White-out on finger touch after drawing
+      with Pencil using a stylus. Only supported on iPad with Apple Pencil. */
+  AUTO_FINGER_WHITEOUT: process.env['AUTO_FINGER_WHITEOUT'] !== "disabled",
 };