If Terran Ruler is enabled, store the length of the traveled path so changes to difficult terrain aren't reflected in the tokens movement history

src/compatibility.js

@@ -14,10 +14,23 @@ export function highlightMeasurementTerrainRuler(ray, startDistance, tokenShape=
 	}
 }
 
-export function measureDistances(segments, token, shape, gridSpaces=true) {
+export function measureDistances(segments, token, shape, gridSpaces=true, options={}) {
+	const opts = duplicate(options)
+	opts.gridSpaces = gridSpaces;
 	const terrainRulerAvailable = game.modules.get("terrain-ruler")?.active && canvas.grid.type !== CONST.GRID_TYPES.GRIDLESS;
-	if (terrainRulerAvailable)
-		return terrainRuler.measureDistances(segments, {costFunction: (x, y) => getCostFromSpeedProvider(token, getAreaFromPositionAndShape({x, y}, shape), {x, y})});
-	else
-		return canvas.grid.measureDistances(segments, { gridSpaces });
+	if (terrainRulerAvailable) {
+		const firstNewSegmentIndex = segments.findIndex(segment => !segment.ray.dragRulerVisitedSpaces);
+		const previousSegments = segments.slice(0, firstNewSegmentIndex);
+		const newSegments = segments.slice(firstNewSegmentIndex);
+		const distances = previousSegments.map(segment => segment.ray.dragRulerVisitedSpaces[segment.ray.dragRulerVisitedSpaces.length - 1].distance);
+		previousSegments.forEach(segment => segment.ray.terrainRulerVisitedSpaces = duplicate(segment.ray.dragRulerVisitedSpaces));
+		opts.costFunction = (x, y) => getCostFromSpeedProvider(token, getAreaFromPositionAndShape({x, y}, shape), {x, y});
+		if (previousSegments.length > 0)
+			opts.terrainRulerInitialState = previousSegments[previousSegments.length - 1];
+		return distances.concat(terrainRuler.measureDistances(newSegments, opts));
+	}
+	else {
+		return canvas.grid.measureDistances(segments, options);
+	}
 }
+

src/foundry_imports.js

@@ -136,6 +136,8 @@ export function measure(destination, {gridSpaces=true, snap=false} = {}) {
 		const centeredRay = new Ray(centeredOrigin, centeredDest)
 		ray.isPrevious = Boolean(origin.isPrevious);
 		centeredRay.isPrevious = ray.isPrevious;
+		ray.dragRulerVisitedSpaces = origin.dragRulerVisitedSpaces;
+		centeredRay.dragRulerVisitedSpaces = ray.dragRulerVisitedSpaces;
 		if (ray.distance < 10) {
 			if (label) label.visible = false;
 			continue;

src/movement_tracking.js

@@ -1,3 +1,6 @@
+import {measureDistances} from "./compatibility.js";
+import {getTokenShape} from "./util.js";
+
 function initTrackingFlag(combatant) {
 	const initialFlag = {passedWaypoints: [], trackedRound: 0};
 	let dragRulerFlag = combatant.flags?.dragRuler;
@@ -37,11 +40,19 @@ export async function trackRays(token, rays) {
 	}
 
 	// Add the passed waypoints to the combatant
-	const waypoints = combatant.flags.dragRuler.passedWaypoints;
+	const terrainRulerAvailable = game.modules.get("terrain-ruler")?.active && canvas.grid.type !== CONST.GRID_TYPES.GRIDLESS;
+	const dragRulerFlags = combatant.flags.dragRuler;
+	const waypoints = dragRulerFlags.passedWaypoints;
 	for (const ray of rays) {
 		// Ignore rays that have the same start and end coordinates
-		if (ray.A.x !== ray.B.x || ray.A.y !== ray.B.y)
+		if (ray.A.x !== ray.B.x || ray.A.y !== ray.B.y) {
+			if (terrainRulerAvailable) {
+				measureDistances([{ray}], token, getTokenShape(token), true, {terrainRulerInitialState: dragRulerFlags.rulerState});
+				ray.A.dragRulerVisitedSpaces = ray.terrainRulerVisitedSpaces;
+				dragRulerFlags.rulerState = ray.terrainRulerFinalState;
+			}
 			waypoints.push(ray.A);
+		}
 	}
 	await combat.updateEmbeddedEntity("Combatant", {_id: combatant._id, flags: combatant.flags}, {diff: false});
 }

src/ruler.js

@@ -70,7 +70,7 @@ export class DragRulerRuler extends Ruler {
 	}
 
 	dragRulerAddWaypointHistory(waypoints) {
-		waypoints = waypoints.map(waypoint => {return {x: waypoint.x, y: waypoint.y, isPrevious: true}});
+		waypoints.forEach(waypoint => waypoint.isPrevious = true);
 		this.waypoints = this.waypoints.concat(waypoints);
 		for (const waypoint of waypoints) {
 			this.labels.addChild(new PreciseText("", CONFIG.canvasTextStyle));