Don't show the drag ruler to players who cannot se the dragged token

As a side effect this will now also show the coloring to other players

CHANGELOG.md

@@ -0,0 +1,4 @@
+# In development
+## New features
+- The drag ruler will now be colored for other players than the dragging player as well
+- The drag ruler won't be shown to other players if they cannot see the dragged token

src/main.js

@@ -6,7 +6,7 @@ import {registerSettings, settingsKey} from "./settings.js"
 Hooks.once("init", () => {
 	registerSettings()
 	hookTokenDragHandlers()
-	hookRulerHandlers()
+	hookRulerFunctions()
 	patchRulerMeasure()
 	patchRulerHighlightMeasurement()
 
@@ -26,12 +26,14 @@ Hooks.once("ready", () => {
 })
 
 Hooks.on("canvasReady", () => {
-	canvas.controls.ruler.draggedToken = null
+	canvas.controls.rulers.children.forEach(ruler => {
-	Object.defineProperty(canvas.controls.ruler, "isDragRuler", {
+		ruler.draggedToken = null
+		Object.defineProperty(ruler, "isDragRuler", {
 			get: function isDragRuler() {
 				return Boolean(this.draggedToken) // If draggedToken is set this is a drag ruler
 			}
 		})
+	})
 })
 
 function hookTokenDragHandlers() {
@@ -62,7 +64,7 @@ function hookTokenDragHandlers() {
 	}
 }
 
-function hookRulerHandlers() {
+function hookRulerFunctions() {
 	const originalMoveTokenHandler = Ruler.prototype.moveToken
 	Ruler.prototype.moveToken = function (event) {
 		const eventHandled = onRulerMoveToken.call(this, event)
@@ -70,6 +72,22 @@ function hookRulerHandlers() {
 			return originalMoveTokenHandler.call(this, event)
 		return true
 	}
+
+	const originalToJSON = Ruler.prototype.toJSON
+	Ruler.prototype.toJSON = function () {
+		const json = originalToJSON.call(this)
+		if (this.draggedToken)
+			json["draggedToken"] = this.draggedToken.data._id
+		return json
+	}
+
+	const originalUpdate = Ruler.prototype.update
+	Ruler.prototype.update = function (data) {
+		if (data.draggedToken) {
+			this.draggedToken = canvas.tokens.get(data.draggedToken)
+		}
+		originalUpdate.call(this, data)
+	}
 }
 
 function onTokenLeftDragStart(event) {
@@ -127,6 +145,10 @@ function patchRulerMeasure() {
 	code = code.slice(code.indexOf("\n"), code.lastIndexOf("\n"))
 	code = strInsertAfter(code, "for ( let [i, d] of distances.entries() ) {\n", "segments[i].startDistance = totalDistance\n")
 	code = strInsertAfter(code, "this._highlightMeasurement(ray", ", s.startDistance")
+
+	// Don't show ruler if the measured token is invisible
+	code = "if (this.isDragRuler && !this.draggedToken.isVisible) return [];" + code
+
 	Ruler.prototype.measure = new Function("destination", "{gridSpaces=true}={}", code)
 }