Work towards gridless difficult terrain pathfinding

This fixes a bug where gridless snapping would snap slightly below the target range

.gitignore

@@ -2,3 +2,4 @@
 artifact/
 wasm/
 *.lock
+.vscode/

CHANGELOG.md

@@ -1,3 +1,31 @@
+## 1.12.8
+### Bugfixes
+- Fixed a bug that could cause grid cells to be highlighted in the wrong color
+
+### Compatibility
+- Fixed an interaction with the Wall Height module that could allow players to walk through walls
+
+
+## 1.12.7
+### Bugfixes
+- Fixed a bug that caused measurement templates to only snap to the corners of the grid (this was a regression introduced in 1.12.5)
+
+
+## 1.12.6
+### Bugfixes
+- Measured templates no longer snap to a virtual grid on gridless scenes (this was a regression introduced in 1.12.5)
+
+
+## 1.12.5
+### Compatibility
+- Drag Ruler is now compatible with DF Template Enhancements
+
+
+## 1.12.4
+### Bugfixes
+- Fixed a bug that could cause Drag Ruler to override the default ruler color on other player's clients
+
+
 ## 1.12.3
 ### Bugfixes
 - Fixed a bug that could cause foundry to freeze indefinitely when trying to pathfind to an unreachalbe location (thanks to JDCalvert)

js/api.js

@@ -2,7 +2,7 @@ import {measureDistances} from "./compatibility.js";
 import {getMovementHistory} from "./movement_tracking.js";
 import {GenericSpeedProvider, SpeedProvider} from "./speed_provider.js"
 import {settingsKey} from "./settings.js"
-import {getTokenShape} from "./util.js";
+import {getAreaFromPositionAndShape, getTokenShape} from "./util.js";
 
 export const availableSpeedProviders = {}
 export let currentSpeedProvider = undefined
@@ -140,6 +140,10 @@ export function getMovedDistanceFromToken(token) {
 	return distances.reduce((acc, val) => acc + val, 0);
 }
 
+export function buildCostFunction(token, shape) {
+	return (x, y, costOptions={}) => getCostFromSpeedProvider(token, getAreaFromPositionAndShape({x, y}, shape), costOptions);
+}
+
 export function registerModule(moduleId, speedProvider) {
 	// Check if a module with the given id exists and is currently enabled
 	const module = game.modules.get(moduleId)

js/compatibility.js

@@ -1,6 +1,6 @@
-import {getCostFromSpeedProvider} from "./api.js";
+import {buildCostFunction} from "./api.js";
 import {settingsKey} from "./settings.js";
-import {getAreaFromPositionAndShape, highlightTokenShape} from "./util.js";
+import {highlightTokenShape} from "./util.js";
 
 export function getHexSizeSupportTokenGridCenter(token) {
 	const tokenCenterOffset = CONFIG.hexSizeSupport.getCenterOffset(token)
@@ -27,7 +27,7 @@ export function measureDistances(segments, entity, shape, options={}) {
 		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, costOptions={}) => {	return getCostFromSpeedProvider(entity, getAreaFromPositionAndShape({x, y}, shape), costOptions); }
+		opts.costFunction = buildCostFunction(entity, shape);
 		if (previousSegments.length > 0)
 			opts.terrainRulerInitialState = previousSegments[previousSegments.length - 1].ray.dragRulerFinalState;
 		return distances.concat(terrainRuler.measureDistances(newSegments, opts));

js/data_structures.js

@@ -0,0 +1,138 @@
+/**
+ * A combination queue/set where the elements are ordered (in ascending order, according to the given priority function)
+ * and unique (according to the given elementMatcher).
+ *
+ * If an element is added to the set and an equivalent element already exists, the lower-priority one is discarded.
+ */
+export class PriorityQueueSet {
+	constructor(elementMatcher, priorityFunction) {
+		this.first = null;
+		this.elementMatcher = elementMatcher;
+		this.priorityFunction = priorityFunction;
+	}
+
+	pushWithPriority(value) {
+		const newNode = {value, priority: this.priorityFunction(value), next: null};
+
+		// If the queue is currently empty, we can just set this new node as the first and we're done
+		if (!this.first) {
+			this.first = newNode;
+			return;
+		}
+
+		let inserted = false;
+		let previous;
+		let current = this.first;
+
+		// Loop through the existing elements
+		while (current) {
+			if (this.elementMatcher(current.value, value)) {
+				// We've found an equivalent element before one with a lower priority. This one has at least
+				// the same priority as the new one, so don't bother inserting
+				return;
+			} else if (newNode.priority <= current.priority) {
+				// We've found some element with lower priority than the new one, so insert the new one just before it
+				newNode.next = current;
+				if (previous) {
+					previous.next = newNode;
+				} else {
+					this.first = newNode;
+				}
+				inserted = true;
+
+				previous = current;
+				current = current.next;
+				break;
+			}
+			previous = current;
+			current = current.next;
+		}
+
+		if (inserted) {
+			// Go through the rest of the list and try to find an equivalent element to the new one.
+			// We know it has higher priority than the new one, so remove it.
+			while (current) {
+				if (this.elementMatcher(current.value, value)) {
+					if (previous) {
+						previous.next = current.next;
+					} else {
+						this.first = current.next;
+					}
+					return;
+				}
+				previous = current;
+				current = current.next;
+			}
+		} else {
+			// We reached the end of the queue without finding a lower-priority or existing element, so
+			// insert the new one at the end
+			previous.next = newNode;
+		}
+	}
+
+	hasNext() {
+		return !!this.first;
+	}
+
+	pop() {
+		const first = this.first;
+		this.first = first?.next;
+		return first?.value;
+	}
+}
+
+/**
+ * Queue that will only ever accept elements with a given value once. Elements must have a "value" field, the
+ * JSON representation of which will be used as the key to match
+ */
+export class ProcessOnceQueue {
+	constructor() {
+		this.first = null;
+		this.last = null;
+		this.previouslyQueued = new Set();
+	}
+
+	/**
+	 * Remove everything from the queue and forget all the previously-queued items
+	 */
+	reset() {
+		this.first = null;
+		this.last = null;
+		this.previouslyQueued.clear();
+	}
+
+	push(element) {
+		if (this.previouslyQueued.has(element)) {
+			return;
+		}
+		this.previouslyQueued.add(element);
+
+		const newNode = {
+			value: element,
+			next: null,
+			previous: null
+		}
+
+		if (!this.first) {
+			this.first = newNode;
+			this.last = newNode;
+		} else {
+			this.last.next = newNode;
+			newNode.previous = this.last;
+			this.last = newNode;
+		}
+	}
+
+	pop() {
+		const node = this.first;
+		this.first = node?.next;
+		if (!node?.next) {
+			this.last = null;
+		}
+		return node?.value;
+	}
+
+	hasNext() {
+		return !!this.first;
+	}
+}

js/foundry_imports.js

@@ -28,6 +28,9 @@ export async function moveEntities(draggedEntity, selectedEntities) {
 		const hasCollision = selectedEntities.some(token => {
 			const offset = calculateEntityOffset(token, draggedEntity);
 			const offsetRays = rays.filter(ray => !ray.isPrevious).map(ray => applyOffsetToRay(ray, offset))
+			if (window.WallHeight) {
+				window.WallHeight.addBoundsToRays(offsetRays, draggedEntity);
+			}
 			return offsetRays.some(r => canvas.walls.checkCollision(r));
 		})
 		if (hasCollision) {
@@ -172,7 +175,9 @@ export function measure(destination, options={}) {
 		const from = getGridPositionFromPixelsObj(this.waypoints[this.waypoints.length - 1]);
 		const to = getGridPositionFromPixelsObj(destination);
 		let path = findPath(from, to, this.draggedEntity, this.waypoints);
-		if (path) {
+		if (path)
+			path.shift();
+		if (path && path.length > 0) {
 			path = path.map(point => getSnapPointForTokenObj(getPixelsFromGridPositionObj(point), this.draggedEntity));
 
 			// If the token is snapped to the grid, the first point of the path is already handled by the ruler
@@ -341,7 +346,8 @@ export function highlightMeasurementNative(ray, previousSegments, tokenShape=[{x
 		if ( x0 === x1 && y0 === y1 ) continue;
 
 		// Highlight the grid position
-		let [xg, yg] = canvas.grid.grid.getPixelsFromGridPosition(x1, y1);
+		let [xgtl, ygtl] = canvas.grid.grid.getPixelsFromGridPosition(x1, y1);
+		let [xg, yg] = canvas.grid.grid.getCenter(xgtl, ygtl);
 		const pathUntilSpace = previousSegments.concat([{ray: new Ray(ray.A, {x: xg, y: yg})}]);
 		const distance = sum(canvas.grid.measureDistances(pathUntilSpace, {gridSpaces: true}));
 		const color = this.dragRulerGetColorForDistance(distance);
@@ -355,7 +361,8 @@ export function highlightMeasurementNative(ray, previousSegments, tokenShape=[{x
 			let th = tMax[i - 1] - (0.5 / nMax);
 			let {x, y} = ray.project(th);
 			let [x1h, y1h] = canvas.grid.grid.getGridPositionFromPixels(x, y);
-			let [xgh, ygh] = canvas.grid.grid.getPixelsFromGridPosition(x1h, y1h);
+			let [xghtl, yghtl] = canvas.grid.grid.getPixelsFromGridPosition(x1h, y1h);
+			let [xgh, ygh] = canvas.grid.grid.getCenter(xghtl, yghtl);
 			const pathUntilSpace = previousSegments.concat([{ray: new Ray(ray.A, {x: xgh, y: ygh})}]);
 			const distance = sum(canvas.grid.measureDistances(pathUntilSpace, {gridSpaces: true}));
 			const color = this.dragRulerGetColorForDistance(distance);

js/hex_support.js

@@ -0,0 +1,93 @@
+/**
+ * Functions taken directly from the hex-size-support module (https://github.com/Ourobor/Hex-Size-Support/releases/tag/1.1.0).
+ * Unless otherwise stated, these functions are taken as-is.
+ */
+
+/**
+ * Altered version of this function.
+ * - Instead of taking a token as a parameter to retrieve the altOrientationFlag, receive the flag value directly
+ * - Instead of taking a grid parameter, get the grid value from the globas canvas
+ */
+export function findVertexSnapPoint(x, y, altOrientationFlag) {
+	const grid = canvas.grid.grid;
+	if (grid.columns) {
+		return findSnapPointCols(x, y, grid.h, grid.w, altOrientationFlag);
+	} else {
+		return findSnapPointRows(x, y, grid.h, grid.w, altOrientationFlag);
+	}
+}
+
+function findSnapPointRows(x, y, h, w, alt) {
+	let xOffset = 0.0
+	if (canvas.grid.grid.even) {
+		xOffset = -0.5
+	}
+
+	let yOffset1 = 0.75
+	let yOffset2 = 0.00
+	if (alt) {
+		yOffset1 = 0.25
+		yOffset2 = 1.00
+	}
+
+	let row1 = calculateSnapPointsRows(x, y, h, w, 0.5 + xOffset, yOffset1);
+	let row2 = calculateSnapPointsRows(x, y, h, w, 1.0 + xOffset, yOffset2);
+
+	let dist1 = Math.pow((row1.x - x), 2) + Math.pow((row1.y - y), 2)
+	let dist2 = Math.pow((row2.x - x), 2) + Math.pow((row2.y - y), 2)
+
+	if (dist1 < dist2) {
+		return row1
+	}
+	else {
+		return row2
+	}
+}
+
+function calculateSnapPointsRows(x, y, h, w, xOff, yOff) {
+	let c = Math.floor(((x + ((0.5 - xOff) * w)) / w) + 1)
+	let r = Math.floor(((y + ((0.75 - yOff) * h)) / (1.5 * h)) + 1)
+
+	let snapX = (c * w) - ((1 - xOff) * w)
+	let snapY = (r * h * 1.5) - ((1.5 - yOff) * h)
+
+	return {x: snapX, y: snapY}
+}
+
+function findSnapPointCols(x, y, h, w, alt) {
+	let yOffset = 0.0
+	if (canvas.grid.grid.even) {
+		yOffset = -0.5
+	}
+
+	let xOffset1 = 0.25
+	let xOffset2 = 1.00
+	if (alt) {
+		xOffset1 = 0.75
+		xOffset2 = 0.00
+	}
+
+	let row1 = calculateSnapPointsCols(x, y, h, w, xOffset1, 0.5 + yOffset);
+	let row2 = calculateSnapPointsCols(x, y, h, w, xOffset2, 1.0 + yOffset);
+
+	let dist1 = Math.pow((row1.x - x), 2) + Math.pow((row1.y - y), 2)
+	let dist2 = Math.pow((row2.x - x), 2) + Math.pow((row2.y - y), 2)
+
+	if (dist1 < dist2) {
+		return row1
+	}
+	else {
+		return row2
+	}
+
+}
+
+function calculateSnapPointsCols(x, y, h, w, xOff, yOff) {
+	let c = Math.floor(((x + ((0.75 - xOff) * w)) / (1.5 * w)) + 1)
+	let r = Math.floor(((y + ((0.5 - yOff) * h)) / h) + 1)
+
+	let snapX = (c * w * 1.5) - ((1.5 - xOff) * w)
+	let snapY = (r * h) - ((1 - yOff) * h)
+
+	return {x: snapX, y: snapY}
+}

js/main.js

@@ -7,7 +7,7 @@ import {disableSnap, registerKeybindings} from "./keybindings.js";
 import {libWrapper} from "./libwrapper_shim.js";
 import {performMigrations} from "./migration.js"
 import {removeLastHistoryEntryIfAt, resetMovementHistory} from "./movement_tracking.js";
-import {wipePathfindingCache, initializePathfinding} from "./pathfinding.js";
+import {wipePathfindingCache, initializePathfinding, startBackgroundCaching, terrainRulerWrapper} from "./pathfinding.js";
 import {extendRuler} from "./ruler.js";
 import {registerSettings, RightClickAction, settingsKey} from "./settings.js"
 import {recalculate} from "./socket.js";
@@ -28,6 +28,21 @@ initGridlessPathfinding().then(() => {
 	Hooks.on("createWall", wipePathfindingCache);
 	Hooks.on("updateWall", wipePathfindingCache);
 	Hooks.on("deleteWall", wipePathfindingCache);
+
+	// Whenever the current user selects a token, start caching
+	Hooks.on("controlToken", (token, controlled) => {
+		if (controlled) {
+			startBackgroundCaching(token);
+		}
+	});
+
+	// Whenever a token the current user controls updates, start caching
+	Hooks.on("updateToken", (document) => {
+		const token = document.object;
+		if (token._controlled) {
+			startBackgroundCaching(token);
+		}
+	});
 });
 
 Hooks.once("init", () => {
@@ -47,6 +62,9 @@ Hooks.once("init", () => {
 		registerSystem,
 		recalculate,
 		resetMovementHistory,
+		private: {
+			terrainRulerWrapper
+		}
 	}
 })
 

js/pathfinding.js

@@ -1,13 +1,238 @@
-import {getGridPositionFromPixelsObj, getPixelsFromGridPositionObj} from "./foundry_fixes.js";
+import {getCenterFromGridPositionObj, getGridPositionFromPixelsObj, getPixelsFromGridPositionObj} from "./foundry_fixes.js";
 import {moveWithoutAnimation, togglePathfinding} from "./keybindings.js";
 import {debugGraphics} from "./main.js";
 import {settingsKey} from "./settings.js";
-import {getSnapPointForTokenObj, iterPairs} from "./util.js";
+import {buildSnapPointTokenData, getSnapPointForTokenDataObj, getTokenShape, getTokenShapeForTokenData, isModuleActive, iterPairs} from "./util.js";
 
-import * as GridlessPathfinding from "../wasm/gridless_pathfinding.js"
+import * as GridlessPathfinding from "../wasm/gridless_pathfinding.js";
+import {PriorityQueueSet, ProcessOnceQueue} from "./data_structures.js";
+import {buildCostFunction} from "./api.js";
+
+class CacheLayer {
+	constructor(tokenData, cacheId) {
+		this.tokenData = tokenData;
+		this.cacheId = cacheId;
+		this.queue = new ProcessOnceQueue();
+
+		this.buildNodes();
+		this.registerUse();
+	}
+
+	buildNodes() {
+		this.nodes = new Array(gridHeight);
+		for (let y = 0; y < gridHeight; y++) {
+			this.nodes[y] = new Array(gridWidth);
+			for (let x = 0; x < gridWidth; x++) {
+				this.nodes[y][x] = {x, y};
+			}
+		}
+	}
+
+	registerUse() {
+		this.lastUsed = Date.now();
+	}
+}
+
+/**
+ * Class to hold all the cached node data, and functions to deal with caching.
+ *
+ * Since pathfinding can depend on several factors, e.g. the token's size, we keep
+ * several caches, keyed by all the data relevant to pathfinding. If we already have
+ * the maximum number of caches and we need to create another one, we discard the
+ * one not used for the longest.
+ *
+ * When we select a token, or a token we have selected updates, we start caching
+ * in the background so, when we do start pathfinding, it's very performant.
+ *
+ * Background caching starts by trying to run an idle process (when the browser is
+ * otherwise not busy), but if it can't do that after an amount of time (e.g. the
+ * CPU is very slow and is busy) then we instead start caching a few nodes each
+ * frame.
+ */
+class Cache {
+	static maxCacheLayers = 5;
+	static maxBackgroundCachingMillis = 10;
+	static maxAnimationCachingMillis = 5;
+	static backgroundCachingTimeoutMillis = 200;
+
+	constructor() {
+		this.layers = new Map();
+		this.background = {
+			nextJobId: null,
+			nextTimeoutId: null,
+			nextAnimationFrameId: null
+		}
+	}
+
+	clear() {
+		this.layers.clear();
+		if (this.background.nextJobId) {
+			window.cancelIdleCallback(this.background.nextJobId);
+			this.background.nextJobId = null;
+		}
+		this.cancelTimeout();
+		this.cancelAnimationFrame();
+	}
+
+	/**
+	 * Retrieve the cache layer for this token, using information that can make a difference to the pathfinding algorithm
+	 * If a layer that suits this token doesn't exist, create one
+	 */
+	getCacheLayer(token) {
+		const tokenData = buildTokenData(token);
+		// TODO Request this from the speed providers so they can set their own options
+		let terrainData = canvas.terrain.listAllTerrain({token});
+		terrainData = terrainData.map(data => {
+			return {
+				x: data.object.x,
+				y: data.object.y,
+				cost: data.cost,
+				shape: data.shape,
+			};
+		});
+		const cacheIdData = {tokenData, terrainData};
+		const cacheId = GridlessPathfinding.sha1(JSON.stringify(cacheIdData));
+		let cacheLayer = this.layers.get(cacheId);
+		// If we don't already have a cache layer for this cache ID, create one now
+		if (!cacheLayer) {
+			// Check if we already have the max number of layers. If we do,
+			// get rid of the one that hasn't been used for the longest
+			if (this.layers.size >= Cache.maxCacheLayers) {
+				const oldestCache = Array.from(this.layers.values())
+					.reduce((layer1, layer2) => (layer1?.lastUsed < layer2.lastUsed) ? layer1 : layer2, null);
+				this.layers.delete(oldestCache.cacheId);
+			}
+
+			// Create the new cache
+			cacheLayer = new CacheLayer(tokenData, cacheId);
+			this.layers.set(cacheId, cacheLayer);
+		} else {
+			// Register that we're using this cache right now
+			cacheLayer.registerUse();
+		}
+
+		return cacheLayer;
+	}
+
+	/**
+	 * Start background caching from the token's current position
+	 */
+	startBackgroundCaching(token) {
+		const cacheLayer = this.getCacheLayer(token);
+		const tokenPosition = getGridPositionFromPixelsObj(token.position)
+
+		cacheLayer.queue.push(cacheLayer.nodes[tokenPosition.y][tokenPosition.x]);
+
+		this.scheduleBackgroundCache();
+	}
+
+	/**
+	 * Find if any of the caches have more nodes to background cache. If there is, then schedule a background
+	 * caching job for that queue
+	 */
+	scheduleBackgroundCache() {
+		// If we already have a nextJobId, then don't start another one
+		if (this.background.nextJobId) return;
+
+		// Find the latest-used cache that has nodes left to cache
+		const latestCache = this.getLatestCacheWithNonEmptyQueue();
+		if (latestCache) {
+			this.background.nextJobId = window.requestIdleCallback(
+				() => this.runBackgroundCache(latestCache)
+			);
+			this.resetAnimationFrameTimeout();
+		}
+	}
+
+	/**
+	 * Start a timeout which, if we reach the timeout time, will schedule a small amount of caching
+	 * to be performed every frame. This timeout will be reset every time we perform background caching.
+	 */
+	resetAnimationFrameTimeout() {
+		this.cancelTimeout();
+		this.cancelAnimationFrame();
+
+		this.background.nextTimeoutId = window.setTimeout(
+			() => {
+				this.scheduleAnimationFrameCache();
+				this.background.nextTimeoutId = null;
+			},
+			Cache.backgroundCachingTimeoutMillis
+		);
+	}
+
+	/**
+	 * Schedule a small amount of caching to be done just before the next frame renders
+	 */
+	scheduleAnimationFrameCache() {
+		const latestCache = this.getLatestCacheWithNonEmptyQueue();
+		if (latestCache) {
+			this.background.nextAnimationFrameId = window.requestAnimationFrame(
+				() => this.runAnimationCache(latestCache)
+			);
+		}
+	}
+
+	/**
+	 * Find which cache was last used and get its cache ID
+	 */
+	getLatestCacheWithNonEmptyQueue() {
+		return Array.from(this.layers.values())
+			.filter(layer => layer.queue.hasNext())
+			.reduce((layer1, layer2) => (layer1?.lastUsed > layer2.lastUsed) ? layer1 : layer2, null);
+	}
+
+	/**
+	 * Cache nodes for a short time, and then schedule another idle job to cache more nodes
+	 */
+	runBackgroundCache(cacheLayer) {
+		const endTime = performance.now() + Cache.maxBackgroundCachingMillis;
+		while (cacheLayer.queue.hasNext() && performance.now() < endTime) {
+			this.cacheNextNode(cacheLayer);
+		}
+
+		this.background.nextJobId = null;
+		this.scheduleBackgroundCache();
+	}
+
+	/**
+	 * Cache nodes for a very short time, then schedule to cache more nodes next frame
+	 */
+	runAnimationCache(cacheLayer) {
+		const endTime = performance.now() + Cache.maxAnimationCachingMillis;
+		while (cacheLayer.queue.hasNext() && performance.now() < endTime) {
+			this.cacheNextNode(cacheLayer);
+		}
+
+		this.background.nextAnimationFrameId = null;
+		this.scheduleAnimationFrameCache();
+	}
+
+	cacheNextNode(cacheLayer) {
+		let node = cacheLayer.queue.pop();
+		getNode(node, cacheLayer);
+		for (let edge of node.edges) {
+			cacheLayer.queue.push(edge.target);
+		}
+	}
+
+	cancelTimeout() {
+		if (this.background.nextTimeoutId) {
+			window.clearTimeout(this.background.nextTimeoutId);
+			this.background.nextTimeoutId = null;
+		}
+	}
+
+	cancelAnimationFrame() {
+		if (this.background.nextAnimationFrameId) {
+			window.cancelAnimationFrame(this.background.nextAnimationFrameId);
+			this.background.nextAnimationFrameId = null;
+		}
+	}
+}
+
+const cache = new Cache();
 
-let cachedNodes = undefined;
-let cacheElevation;
 let use5105 = false;
 let gridlessPathfinders = new Map();
 let gridWidth, gridHeight;
@@ -23,72 +248,117 @@ export function isPathfindingEnabled() {
 }
 
 export function findPath(from, to, token, previousWaypoints) {
-	checkCacheValid(token);
-
 	if (canvas.grid.type === CONST.GRID_TYPES.GRIDLESS) {
 		let tokenSize = Math.max(token.data.width, token.data.height) * canvas.dimensions.size;
 		let pathfinder = gridlessPathfinders.get(tokenSize);
 		if (!pathfinder) {
-			pathfinder = GridlessPathfinding.initialize(canvas.walls.placeables, tokenSize, token.data.elevation, Boolean(game.modules.get("levels")?.active));
+			let radiusMultiplier = game.settings.get(settingsKey, "pathfindingRadius");
+			// TODO Pass proper options to listAllTerrain
+			// TODO Wipe caches when they become invalid
+			// TODO Multiple caches, analog to gridded pathfinding
+			pathfinder = GridlessPathfinding.initialize(canvas.walls.placeables, canvas.terrain.listAllTerrain(), tokenSize * radiusMultiplier, token.data.elevation, Boolean(game.modules.get("wall-height")?.active));
 			gridlessPathfinders.set(tokenSize, pathfinder);
 		}
 		paintGridlessPathfindingDebug(pathfinder);
 		return GridlessPathfinding.findPath(pathfinder, from, to);
+	} else {
+		const cacheLayer = cache.getCacheLayer(token);
+		const firstNode = calculatePath(from, to, cacheLayer, previousWaypoints);
+		if (!firstNode)
+			return null;
+		paintGriddedPathfindingDebug(firstNode, cacheLayer.tokenData);
+		const path = [];
+		let currentNode = firstNode;
+		while (currentNode) {
+			if (path.length >= 2 && !stepCollidesWithWall(path[path.length - 2], currentNode.node, cacheLayer.tokenData)) {
+				// Replace last waypoint if the current waypoint leads to a valid path that isn't longer than the old path
+				if (window.terrainRuler) {
+					let startNode = getCenterFromGridPositionObj(path[path.length - 2]);
+					let middleNode = getCenterFromGridPositionObj(path[path.length - 1]);
+					let endNode = getCenterFromGridPositionObj(currentNode.node);
+					let oldPath = [{ray: new Ray(startNode, middleNode)}, {ray: new Ray(middleNode, endNode)}];
+					let newPath = [{ray: new Ray(startNode, endNode)}];
+					let costFunction = buildCostFunction(token, getTokenShape(token));
+					// TODO Cache the used measurement for use in the next loop to improve performance
+					let oldDistance = terrainRuler.measureDistances(oldPath, {costFunction}).reduce((a, b) => a + b);
+					let newDistance = terrainRuler.measureDistances(newPath, {costFunction})[0];
+
+					// TODO We might need to check if the diagonal count has increased on 5-10-5
+					if (newDistance < oldDistance)  {
+						path.pop();
+					}
+					else if (newDistance === oldDistance) {
+						let oldNoDiagonals = oldPath[1].ray.terrainRulerFinalState?.noDiagonals;
+						let newNoDiagonals = newPath[0].ray.terrainRulerFinalState?.noDiagonals;
+						// This uses === && < instead of <= because the variables might be undefined (which shall lead to a true result)
+						if (oldNoDiagonals === newNoDiagonals || newNoDiagonals < oldNoDiagonals) {
+							path.pop();
+						}
+					}
 				}
 				else {
-		const lastNode = calculatePath(from, to, token, previousWaypoints);
-		if (!lastNode)
-			return null;
-		paintGriddedPathfindingDebug(lastNode, token);
-		const path = [];
-		let currentNode = lastNode;
-		while (currentNode) {
-			// TODO Check if the distance doesn't change
-			if (path.length >= 2 && !stepCollidesWithWall(path[path.length - 2], currentNode.node, token))
-				// Replace last waypoint if the current waypoint leads to a valid path
-				path[path.length - 1] = {x: currentNode.node.x, y: currentNode.node.y};
-			else
+					path.pop();
+				}
+			}
 			path.push({x: currentNode.node.x, y: currentNode.node.y});
-			currentNode = currentNode.previous;
+			currentNode = currentNode.next;
 		}
 		return path;
 	}
 }
 
-function getNode(pos, token, initialize=true) {
-	pos = {layer: 0, ...pos}; // Copy pos and set pos.layer to the default value if it's unset
-	if (!cachedNodes)
-		cachedNodes = new Array(2);
-	if (!cachedNodes[pos.layer])
-		cachedNodes[pos.layer] = new Array(Math.ceil(canvas.dimensions.height / canvas.grid.h));
-	if (!cachedNodes[pos.layer][pos.y])
-		cachedNodes[pos.layer][pos.y] = new Array(Math.ceil(canvas.dimensions.width / canvas.grid.w));
-	if (!cachedNodes[pos.layer][pos.y][pos.x]) {
-		cachedNodes[pos.layer][pos.y][pos.x] = pos;
+export function terrainRulerWrapper(from, to) {
+	// TODO Send list of terrain to terrain layer
+	const ray = new Ray(from, to);
+	return terrainRuler.measureDistances([{ray}])[0] / canvas.dimensions.distance * canvas.dimensions.size;
+}
+
+function buildTokenData(token) {
+	// Almost all the information we need is for calculating the snap point
+	const tokenData = buildSnapPointTokenData(token);
+
+	// If Wall Height is enabled, which walls matter depends on the token's elevation.
+	// Depending on the settings in Wall Height, the height we care about is either their
+	// foot height (elevation) or eye height (losHeight).
+	if (isModuleActive("wall-height")) {
+		const blockSightMovement = game.settings.get("wall-height", "blockSightMovement");
+		tokenData.elevation = blockSightMovement ? token.losHeight : token.data.elevation;
 	}
 
-	const node = cachedNodes[pos.layer][pos.y][pos.x];
+	return tokenData;
+}
+
+function getNode(pos, cacheLayer, initialize = true) {
+	const node = cacheLayer.nodes[pos.y][pos.x];
 	if (initialize && !node.edges) {
 		node.edges = [];
 		for (const neighborPos of canvas.grid.grid.getNeighbors(pos.y, pos.x).map(([y, x]) => {return {x, y};})) {
-			if (neighborPos.x < 0 || neighborPos.y < 0 || neighborPos.x > gridWidth || neighborPos.y > gridHeight) {
+			if (neighborPos.x < 0 || neighborPos.y < 0 || neighborPos.x >= gridWidth || neighborPos.y >= gridHeight) {
 				continue;
 			}
 
 			// TODO Work with pixels instead of grid locations
-			if (!stepCollidesWithWall(neighborPos, pos, token)) {
+			if (!stepCollidesWithWall(pos, neighborPos, cacheLayer.tokenData)) {
 				const isDiagonal = node.x !== neighborPos.x && node.y !== neighborPos.y && canvas.grid.type === CONST.GRID_TYPES.SQUARE;
-				let targetLayer = pos.layer;
-				if (use5105 && isDiagonal)
-					targetLayer = 1 - targetLayer;
-				const neighbor = getNode({...neighborPos, layer: targetLayer}, token, false);
-
-				// TODO We currently assume a cost of one or two for all transitions. Change this for difficult terrain support
-				let edgeCost = 1;
-				if (isDiagonal) {
-					// We charge 0.0001 more for edges to avoid unnecessary diagonal steps
-					edgeCost = pos.layer === 1 && targetLayer === 0 ? 2 : 1.0001;
+				let edgeCost;
+				if (window.terrainRuler) {
+					let ray = new Ray(getCenterFromGridPositionObj(pos), getCenterFromGridPositionObj(neighborPos));
+					let measuredDistance = terrainRuler.measureDistances([{ray}], {costFunction: buildCostFunction(cacheLayer.tokenData, getTokenShapeForTokenData(cacheLayer.tokenData))})[0];
+					edgeCost = Math.round(measuredDistance / canvas.dimensions.distance);
+					if (ray.terrainRulerFinalState?.noDiagonals === 1) {
+						edgeCost = 1.5;
 					}
+					// Charge 1.0001 instead of 1 for diagonals to discourage unnecessary diagonals
+					if (isDiagonal && edgeCost == 1) {
+						edgeCost = 1.0001;
+					}
+				}
+				else {
+					// Count 5-10-5 diagonals as 1.5 (so two add up to 3) and 5-5-5 diagonals as 1.0001 (to discourage unnecessary diagonals)
+					// TODO Account for difficult terrain
+					edgeCost = isDiagonal ? (use5105 ? 1.5 : 1.0001) : 1;
+				}
+				const neighbor = getNode(neighborPos, cacheLayer, false);
 				node.edges.push({target: neighbor, cost: edgeCost});
 			}
 		}
@@ -96,44 +366,67 @@ function getNode(pos, token, initialize=true) {
 	return node;
 }
 
-function calculatePath(from, to, token, previousWaypoints) {
-	if (game.system.id === "pf2e")
-		use5105 = true;
-	if (canvas.grid.diagonalRule === "5105")
-		use5105 = true;
-	let startLayer = 0;
+function calculatePath(from, to, cacheLayer, previousWaypoints) {
+	use5105 = game.system.id === "pf2e" || canvas.grid.diagonalRule === "5105";
+	let startCost = 0;
 	if (use5105 && canvas.grid.type === CONST.GRID_TYPES.SQUARE) {
 		previousWaypoints = previousWaypoints.map(w => getGridPositionFromPixelsObj(w));
-		startLayer = calcNoDiagonals(previousWaypoints) % 2;
+		startCost = (calcNoDiagonals(previousWaypoints) % 2) * 0.5;
 	}
-	const nextNodes = [{node: getNode({...to, layer: startLayer}, token), cost: 0, estimated: estimateCost(to, from), previous: null}];
+
+	const nextNodes = new PriorityQueueSet((node1, node2) => node1.node === node2.node, node => node.estimated);
 	const previousNodes = new Set();
-	while (nextNodes.length > 0) {
-		// Sort by estimated cost, high to low
-		// TODO Re-sorting every iteration is expensive. Think of something better
-		nextNodes.sort((a, b) => b.estimated - a.estimated);
+
+	nextNodes.pushWithPriority(
+		{
+			node: getNode(from, cacheLayer),
+			cost: startCost,
+			estimated: startCost + estimateCost(from, to),
+			previous: null
+		}
+	);
+
+	while (nextNodes.hasNext()) {
 		// Get node with cheapest estimate
 		const currentNode = nextNodes.pop();
-		if (currentNode.node.x === from.x && currentNode.node.y === from.y)
-			return currentNode;
+		if (currentNode.node.x === to.x && currentNode.node.y === to.y) {
+			return buildPathNodes(currentNode);
+		}
 		previousNodes.add(currentNode.node);
 		for (const edge of currentNode.node.edges) {
-			const neighborNode = getNode(edge.target, token);
-			if (previousNodes.has(neighborNode))
+			const neighborNode = getNode(edge.target, cacheLayer);
+			if (previousNodes.has(neighborNode)) {
 				continue;
-			const neighbor = {node: neighborNode, cost: currentNode.cost + edge.cost, estimated: currentNode.cost + edge.cost + estimateCost(neighborNode, from), previous: currentNode};
-			const neighborIndex = nextNodes.findIndex(node => node.node === neighbor.node);
-			if (neighborIndex >= 0) {
-				// If the neighbor is cheaper to reach via the current route than through previously discovered routes, replace it
-				if (nextNodes[neighborIndex].cost > neighbor.cost) {
-					nextNodes[neighborIndex] = neighbor;
+			}
+
+			const neighbor = {
+				node: neighborNode,
+				cost: currentNode.cost + edge.cost,
+				estimated: currentNode.cost + edge.cost + estimateCost(neighborNode, to),
+				previous: currentNode
+			};
+			nextNodes.pushWithPriority(neighbor);
 		}
 	}
-			else {
-				nextNodes.push(neighbor);
-			}
+}
+
+/**
+ * Now we've found the path, we know the final node, and each node links to the previous one.
+ * Reverse this list and return the first node in the path, with each node linking to the next
+ */
+function buildPathNodes(lastNode) {
+	let currentNode = lastNode;
+	let previousNode = null;
+	while (currentNode) {
+		const pathNode = {
+			node: currentNode.node,
+			cost: currentNode.cost,
+			next: previousNode
 		}
+		previousNode = pathNode;
+		currentNode = currentNode.previous;
 	}
+	return previousNode;
 }
 
 function calcNoDiagonals(waypoints) {
@@ -144,18 +437,30 @@ function calcNoDiagonals(waypoints) {
 	return diagonals;
 }
 
+/**
+ * Estimate the travel distance between two points, as the crow flies. Most of the time, this is 1
+ * per space, but for a square grid using 5-10-5 diagonals, count each diagonal as an extra 0.5
+ */
 function estimateCost(pos, target) {
-	return Math.max(Math.abs(pos.x - target.x), Math.abs(pos.y - target.y));
+	const distX = Math.abs(pos.x - target.x);
+	const distY = Math.abs(pos.y - target.y);
+	return Math.max(distX, distY) + (use5105 ? Math.min(distX, distY) * 0.5 : 0);
 }
 
-function stepCollidesWithWall(from, to, token) {
-	const stepStart = getSnapPointForTokenObj(getPixelsFromGridPositionObj(from), token);
-	const stepEnd = getSnapPointForTokenObj(getPixelsFromGridPositionObj(to), token);
+function stepCollidesWithWall(from, to, tokenData) {
+	const stepStart = getSnapPointForTokenDataObj(getPixelsFromGridPositionObj(from), tokenData);
+	const stepEnd = getSnapPointForTokenDataObj(getPixelsFromGridPositionObj(to), tokenData);
+	if (isModuleActive("levels")) {
+		stepStart.z = tokenData.elevation;
+		stepEnd.z = tokenData.elevation;
+		return _levels.testCollision(stepStart, stepEnd, "collision")
+	} else {
 		return canvas.walls.checkCollision(new Ray(stepStart, stepEnd));
+	}
 }
 
 export function wipePathfindingCache() {
-	cachedNodes = undefined;
+	cache.clear();
 	for (const pathfinder of gridlessPathfinders.values()) {
 		GridlessPathfinding.free(pathfinder);
 	}
@@ -164,39 +469,34 @@ export function wipePathfindingCache() {
 		debugGraphics.removeChildren().forEach(c => c.destroy());
 }
 
-/**
- * Check if the current cache is still suitable for the path we're about to find. If not, clear the cache
- */
- function checkCacheValid(token) {
-	// If levels is enabled, the cache is invalid if it was made for a
-	if (game.modules.get("levels")?.active) {
-		const tokenElevation = token.data.elevation;
-		if (tokenElevation !== cacheElevation) {
-			cacheElevation = tokenElevation;
-			wipePathfindingCache();
-		}
-	}
-}
-
 export function initializePathfinding() {
 	gridWidth = Math.ceil(canvas.dimensions.width / canvas.grid.w);
 	gridHeight = Math.ceil(canvas.dimensions.height / canvas.grid.h);
 }
 
-function paintGriddedPathfindingDebug(lastNode, token) {
+export function startBackgroundCaching(token) {
+	// Background caching isn't yet supported for gridless scenes
+	if (canvas.grid.type === CONST.GRID_TYPES.GRIDLESS)
+		return;
+	if (game.user.isGM || game.settings.get(settingsKey, "allowPathfinding")) {
+		cache.startBackgroundCaching(token);
+	}
+}
+
+function paintGriddedPathfindingDebug(firstNode, tokenData) {
 	if (!CONFIG.debug.dragRuler)
 		return;
 
 	debugGraphics.removeChildren().forEach(c => c.destroy());
-	let currentNode = lastNode;
+	let currentNode = firstNode;
 	while (currentNode) {
-		let text = new PIXI.Text(currentNode.cost.toFixed(0));
-		let pixels = getSnapPointForTokenObj(getPixelsFromGridPositionObj(currentNode.node), token);
+		let text = new PIXI.Text(currentNode.cost.toFixed(1));
+		let pixels = getSnapPointForTokenDataObj(getPixelsFromGridPositionObj(currentNode.node), tokenData);
 		text.anchor.set(0.5, 1.0);
 		text.x = pixels.x;
 		text.y = pixels.y;
 		debugGraphics.addChild(text);
-		currentNode = currentNode.previous;
+		currentNode = currentNode.next;
 	}
 }
 

js/ruler.js

@@ -54,6 +54,9 @@ export function extendRuler() {
 				else
 					this.draggedEntity = canvas.templates.get(data.draggedEntity);
 			}
+			else {
+				this.draggedEntity = undefined;
+			}
 
 			super.update(data);
 		}

js/settings.js

@@ -1,5 +1,6 @@
 import {availableSpeedProviders, currentSpeedProvider, getDefaultSpeedProvider, updateSpeedProvider} from "./api.js";
 import {SpeedProvider} from "./speed_provider.js"
+import {wipePathfindingCache} from "./pathfinding.js"
 import { early_isGM } from "./util.js";
 
 export const settingsKey = "drag-ruler";
@@ -100,10 +101,18 @@ export function registerSettings() {
 	game.settings.register(settingsKey, "autoPathfinding", {
 		name: "drag-ruler.settings.autoPathfinding.name",
 		hint: "drag-ruler.settings.autoPathfinding.hint",
-		scpoe: "client",
+		scope: "client",
 		config: early_isGM() || game.settings.get(settingsKey, "allowPathfinding"),
 		type: Boolean,
-		defualt: false,
+		default: false,
+	});
+
+	game.settings.register(settingsKey, "pathfindingRadius", {
+		scope: "world",
+		config: false,
+		type: Number,
+		default: 0.9,
+		onChange: wipePathfindingCache,
 	});
 
 	game.settings.register(settingsKey, "lastTerrainRulerHintTime", {

js/util.js

@@ -1,5 +1,6 @@
 import {getPixelsFromGridPosition} from "./foundry_fixes.js"
-import { disableSnap } from "./keybindings.js";
+import {findVertexSnapPoint} from "./hex_support.js";
+import {disableSnap} from "./keybindings.js";
 
 export function* zip(it1, it2) {
 	for (let i = 0;i < Math.min(it1.length, it2.length);i++) {
@@ -25,14 +26,38 @@ export function sum(arr) {
 	return arr.reduce((a, b) => a + b, 0);
 }
 
+export function buildSnapPointTokenData(token) {
+	const tokenData = {
+		width: token.data.width,
+		height: token.data.height
+	};
+
+	if (isModuleActive("hex-size-support")) {
+		tokenData.hexSizeSupport = {};
+		tokenData.hexSizeSupport.altSnappingFlag = CONFIG.hexSizeSupport.getAltSnappingFlag(token);
+		tokenData.hexSizeSupport.altOrientationFlag = CONFIG.hexSizeSupport.getAltOrientationFlag(token);
+		tokenData.hexSizeSupport.borderSize = token.document.getFlag("hex-size-support", "borderSize");
+	}
+
+	return tokenData;
+}
+
 export function getSnapPointForToken(x, y, token) {
+	return getSnapPointForTokenData(x, y, buildSnapPointTokenData(token));
+}
+
+export function getSnapPointForTokenDataObj(pos, tokenData) {
+	return getSnapPointForTokenData(pos.x, pos.y, tokenData);
+}
+
+function getSnapPointForTokenData(x, y, tokenData) {
 	if (canvas.grid.type === CONST.GRID_TYPES.GRIDLESS) {
 		return new PIXI.Point(x, y);
 	}
 	if (canvas.grid.isHex) {
-		if (game.modules.get("hex-size-support")?.active && CONFIG.hexSizeSupport.getAltSnappingFlag(token)) {
-			if (token.document.getFlag("hex-size-support", "borderSize") % 2 === 0) {
-				const snapPoint = CONFIG.hexSizeSupport.findVertexSnapPoint(x, y, token, canvas.grid.grid)
+		if (tokenData.hexSizeSupport?.altSnappingFlag) {
+			if (tokenData.hexSizeSupport.borderSize % 2 === 0) {
+				const snapPoint = findVertexSnapPoint(x, y, tokenData.hexSizeSupport.altOrientationFlag);
 				return new PIXI.Point(snapPoint.x, snapPoint.y)
 			}
 			else {
@@ -46,38 +71,38 @@ export function getSnapPointForToken(x, y, token) {
 
 	const [topLeftX, topLeftY] = canvas.grid.getTopLeft(x, y);
 	let cellX, cellY;
-	if (token.data.width % 2 === 0)
+	if (tokenData.width % 2 === 0)
 		cellX = x - canvas.grid.h / 2;
 	else
 		cellX = x;
-	if (token.data.height % 2 === 0)
+	if (tokenData.height % 2 === 0)
 		cellY = y - canvas.grid.h / 2;
 	else
 		cellY = y;
 	const [centerX, centerY] = canvas.grid.getCenter(cellX, cellY);
 	let snapX, snapY;
 	// Tiny tokens can snap to the cells corners
-	if (token.data.width <= 0.5) {
+	if (tokenData.width <= 0.5) {
 		const offsetX = x - topLeftX;
 		const subGridWidth = Math.floor(canvas.grid.w / 2);
 		const subGridPosX = Math.floor(offsetX / subGridWidth);
 		snapX = topLeftX + (subGridPosX + 0.5) * subGridWidth;
 	}
 	// Tokens with odd multipliers (1x1, 3x3, ...) and tokens smaller than 1x1 but bigger than 0.5x0.5 snap to the center of the grid cell
-	else if (Math.round(token.data.width) % 2 === 1 || token.data.width < 1) {
+	else if (Math.round(tokenData.width) % 2 === 1 || tokenData.width < 1) {
 		snapX = centerX;
 	}
 	// All remaining tokens (those with even or fractional multipliers on square grids) snap to the intersection points of the grid
 	else {
 		snapX = centerX + canvas.grid.w / 2;
 	}
-	if (token.data.height <= 0.5) {
+	if (tokenData.height <= 0.5) {
 		const offsetY = y - topLeftY;
 		const subGridHeight = Math.floor(canvas.grid.h / 2);
 		const subGridPosY = Math.floor(offsetY / subGridHeight);
 		snapY = topLeftY + (subGridPosY + 0.5) * subGridHeight;
 	}
-	else if (Math.round(token.data.height) % 2 === 1 || token.data.height < 1) {
+	else if (Math.round(tokenData.height) % 2 === 1 || tokenData.height < 1) {
 		snapY = centerY;
 	}
 	else {
@@ -94,23 +119,7 @@ export function getSnapPointForMeasuredTemplate(x, y) {
 	if (canvas.grid.type === CONST.GRID_TYPES.GRIDLESS) {
 		return new PIXI.Point(x, y);
 	}
-	let subgridWidth, subgridHeight;
-	if (canvas.grid.type === CONST.GRID_TYPES.SQUARE) {
-		subgridWidth = subgridHeight = canvas.dimensions.size / 2;
-	}
-	else {
-		if (canvas.grid.grid.columns) {
-			subgridWidth = canvas.grid.w / 4;
-			subgridHeight = canvas.grid.h / 2;
-		}
-		else {
-			subgridWidth = canvas.grid.w / 2;
-			subgridHeight = canvas.grid.h / 4;
-		}
-	}
-	const snappedX = Math.round(x / subgridWidth) * subgridWidth;
-	const snappedY = Math.round(y / subgridHeight) * subgridHeight;
-	return new PIXI.Point(snappedX, snappedY);
+	return canvas.grid.grid.getSnappedPosition(x, y, canvas.templates.gridPrecision);
 }
 
 export function getSnapPointForEntity(x, y, entity) {
@@ -158,15 +167,19 @@ export function getAreaFromPositionAndShape(position, shape) {
 }
 
 export function getTokenShape(token) {
-	if (token.scene.data.gridType === CONST.GRID_TYPES.GRIDLESS) {
+	return getTokenShapeForTokenData(buildSnapPointTokenData(token), token.scene);
+}
+
+export function getTokenShapeForTokenData(tokenData, scene=canvas.scene) {
+	if (scene.data.gridType === CONST.GRID_TYPES.GRIDLESS) {
 		return [{x: 0, y: 0}]
 	}
-	else if (token.scene.data.gridType === CONST.GRID_TYPES.SQUARE) {
-		const topOffset = -Math.floor(token.data.height / 2)
-		const leftOffset = -Math.floor(token.data.width / 2)
+	else if (scene.data.gridType === CONST.GRID_TYPES.SQUARE) {
+		const topOffset = -Math.floor(tokenData.height / 2)
+		const leftOffset = -Math.floor(tokenData.width / 2)
 		const shape = []
-		for (let y = 0;y < token.data.height;y++) {
-			for (let x = 0;x < token.data.width;x++) {
+		for (let y = 0;y < tokenData.height;y++) {
+			for (let x = 0;x < tokenData.width;x++) {
 				shape.push({x: x + leftOffset, y: y + topOffset})
 			}
 		}
@@ -174,8 +187,8 @@ export function getTokenShape(token) {
 	}
 	else {
 		// Hex grids
-		if (game.modules.get("hex-size-support")?.active && CONFIG.hexSizeSupport.getAltSnappingFlag(token)) {
-			const borderSize = token.data.flags["hex-size-support"].borderSize;
+		if (game.modules.get("hex-size-support")?.active && tokenData.hexSizeSupport.altSnappingFlag) {
+			const borderSize = tokenData.hexSizeSupport.borderSize;
 			let shape = [{x: 0, y: 0}];
 			if (borderSize >= 2)
 				shape = shape.concat([{x: 0, y: -1}, {x: -1, y: -1}]);
@@ -184,7 +197,7 @@ export function getTokenShape(token) {
 			if (borderSize >= 4)
 				shape = shape.concat([{x: -2, y: -1}, {x: 1, y: -1}, {x: -1, y: -2}, {x: 0, y: -2}, {x: 1, y: -2}])
 
-			if (Boolean(CONFIG.hexSizeSupport.getAltOrientationFlag(token)) !== canvas.grid.grid.options.columns)
+			if (Boolean(tokenData.hexSizeSupport.altOrientationFlag) !== canvas.grid.grid.options.columns)
 				shape.forEach(space => space.y *= -1);
 			if (canvas.grid.grid.options.columns)
 				shape = shape.map(space => {return {x: space.y, y: space.x}});
@@ -279,3 +292,7 @@ export function early_isGM() {
 	const gmLevel = CONST.USER_ROLES.ASSISTANT;
 	return level >= gmLevel;
 }
+
+export function isModuleActive(moduleName) {
+	return game.modules.get(moduleName)?.active
+}

module.json

@@ -2,7 +2,7 @@
 	"name": "drag-ruler",
 	"title": "Drag Ruler",
 	"description": "When dragging a token displays a ruler showing how far you've moved that token.",
-	"version": "1.12.3",
+	"version": "1.12.8",
 	"minimumCoreVersion" : "9.245",
 	"compatibleCoreVersion" : "9",
 	"authors": [
@@ -65,7 +65,7 @@
 	],
 	"socket": true,
 	"url": "https://github.com/manuelVo/foundryvtt-drag-ruler",
-	"download": "https://github.com/manuelVo/foundryvtt-drag-ruler/releases/download/v1.12.3/drag-ruler-1.12.3.zip",
+	"download": "https://github.com/manuelVo/foundryvtt-drag-ruler/releases/download/v1.12.8/drag-ruler-1.12.8.zip",
 	"manifest": "https://raw.githubusercontent.com/manuelVo/foundryvtt-drag-ruler/master/module.json",
 	"readme": "https://github.com/manuelVo/foundryvtt-drag-ruler/blob/master/README.md",
 	"changelog": "https://github.com/manuelVo/foundryvtt-drag-ruler/blob/master/CHANGELOG.md",

rust/Cargo.lock

@@ -2,6 +2,15 @@
 # It is not intended for manual editing.
 version = 3
 
+[[package]]
+name = "block-buffer"
+version = "0.10.2"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "0bf7fe51849ea569fd452f37822f606a5cabb684dc918707a0193fd4664ff324"
+dependencies = [
+ "generic-array",
+]
+
 [[package]]
 name = "bumpalo"
 version = "3.9.1"
@@ -24,13 +33,53 @@ dependencies = [
  "wasm-bindgen",
 ]
 
+[[package]]
+name = "cpufeatures"
+version = "0.2.2"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "59a6001667ab124aebae2a495118e11d30984c3a653e99d86d58971708cf5e4b"
+dependencies = [
+ "libc",
+]
+
+[[package]]
+name = "crypto-common"
+version = "0.1.3"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "57952ca27b5e3606ff4dd79b0020231aaf9d6aa76dc05fd30137538c50bd3ce8"
+dependencies = [
+ "generic-array",
+ "typenum",
+]
+
+[[package]]
+name = "digest"
+version = "0.10.3"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "f2fb860ca6fafa5552fb6d0e816a69c8e49f0908bf524e30a90d97c85892d506"
+dependencies = [
+ "block-buffer",
+ "crypto-common",
+]
+
+[[package]]
+name = "generic-array"
+version = "0.14.5"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "fd48d33ec7f05fbfa152300fdad764757cbded343c1aa1cff2fbaf4134851803"
+dependencies = [
+ "typenum",
+ "version_check",
+]
+
 [[package]]
 name = "gridless-pathfinding"
-version = "1.12.3"
+version = "1.12.8"
 dependencies = [
  "console_error_panic_hook",
  "js-sys",
  "rustc-hash",
+ "sha1",
  "wasm-bindgen",
 ]
 
@@ -49,6 +98,12 @@ version = "1.4.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "e2abad23fbc42b3700f2f279844dc832adb2b2eb069b2df918f455c4e18cc646"
 
+[[package]]
+name = "libc"
+version = "0.2.125"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "5916d2ae698f6de9bfb891ad7a8d65c09d232dc58cc4ac433c7da3b2fd84bc2b"
+
 [[package]]
 name = "log"
 version = "0.4.14"
@@ -82,6 +137,17 @@ version = "1.1.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "08d43f7aa6b08d49f382cde6a7982047c3426db949b1424bc4b7ec9ae12c6ce2"
 
+[[package]]
+name = "sha1"
+version = "0.10.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "c77f4e7f65455545c2153c1253d25056825e77ee2533f0e41deb65a93a34852f"
+dependencies = [
+ "cfg-if",
+ "cpufeatures",
+ "digest",
+]
+
 [[package]]
 name = "syn"
 version = "1.0.86"
@@ -93,12 +159,24 @@ dependencies = [
  "unicode-xid",
 ]
 
+[[package]]
+name = "typenum"
+version = "1.15.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "dcf81ac59edc17cc8697ff311e8f5ef2d99fcbd9817b34cec66f90b6c3dfd987"
+
 [[package]]
 name = "unicode-xid"
 version = "0.2.2"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "8ccb82d61f80a663efe1f787a51b16b5a51e3314d6ac365b08639f52387b33f3"
 
+[[package]]
+name = "version_check"
+version = "0.9.4"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "49874b5167b65d7193b8aba1567f5c7d93d001cafc34600cee003eda787e483f"
+
 [[package]]
 name = "wasm-bindgen"
 version = "0.2.79"

rust/Cargo.toml

@@ -1,6 +1,6 @@
 [package]
 name = "gridless-pathfinding"
-version = "1.12.3"
+version = "1.12.8"
 edition = "2021"
 
 # See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html
@@ -16,4 +16,5 @@ lto = true
 console_error_panic_hook = "0.1.7"
 js-sys = "0.3.56"
 rustc-hash = "1.1.0"
+sha1 = "0.10.1"
 wasm-bindgen = "0.2.79"

rust/src/geometry.rs

@@ -38,6 +38,11 @@ impl Point {
 		let e = 0.000001;
 		(self.x - other.x).abs() < e && (self.y - other.y).abs() < e
 	}
+
+	pub fn is_in_rectangle(&self, rect: &Rectangle) -> bool {
+		between(self.x, rect.left.p1.x, rect.right.p1.x)
+			&& between(self.y, rect.top.p1.y, rect.bottom.p1.y)
+	}
 }
 
 impl Eq for Point {}
@@ -179,9 +184,70 @@ impl LineSegment {
 		}
 		between(intersection.x, self.p1.x, self.p2.x)
 	}
+
+	pub fn intersects_rect(&self, rect: &Rectangle) -> bool {
+		if self.p1.is_in_rectangle(rect) {
+			return true;
+		}
+		[rect.left, rect.top, rect.right, rect.bottom]
+			.iter()
+			.any(|edge| self.intersection(edge).is_some())
+	}
 }
 
 pub fn between<T: Copy + PartialOrd>(num: T, a: T, b: T) -> bool {
 	let (min, max) = if a < b { (a, b) } else { (b, a) };
 	num >= min && num <= max
 }
+
+#[wasm_bindgen]
+extern "C" {
+	pub type JsRectangle;
+
+	#[wasm_bindgen(method, getter)]
+	fn left(this: &JsRectangle) -> f64;
+
+	#[wasm_bindgen(method, getter)]
+	fn top(this: &JsRectangle) -> f64;
+
+	#[wasm_bindgen(method, getter)]
+	fn right(this: &JsRectangle) -> f64;
+
+	#[wasm_bindgen(method, getter)]
+	fn bottom(this: &JsRectangle) -> f64;
+}
+
+#[derive(Debug, Clone, Copy)]
+pub struct Rectangle {
+	pub left: LineSegment,
+	pub top: LineSegment,
+	pub right: LineSegment,
+	pub bottom: LineSegment,
+}
+
+impl Rectangle {
+	pub fn new(left: f64, top: f64, right: f64, bottom: f64) -> Self {
+		Self {
+			left: LineSegment::new(Point::new(left, top), Point::new(left, bottom)),
+			top: LineSegment::new(Point::new(left, top), Point::new(right, top)),
+			right: LineSegment::new(Point::new(right, top), Point::new(right, bottom)),
+			bottom: LineSegment::new(Point::new(left, bottom), Point::new(right, bottom)),
+		}
+	}
+}
+
+impl From<&JsRectangle> for Rectangle {
+	fn from(rect: &JsRectangle) -> Self {
+		let left = rect.left();
+		let top = rect.top();
+		let right = rect.right();
+		let bottom = rect.bottom();
+		Self::new(left, top, right, bottom)
+	}
+}
+
+#[derive(Debug, Copy, Clone)]
+pub struct Circle {
+	pub center: Point,
+	pub radius: f64,
+}

rust/src/js_api.rs

@@ -1,9 +1,11 @@
 use js_sys::Array;
+use sha1::{Digest, Sha1};
 use wasm_bindgen::prelude::*;
 
 use crate::{
-	geometry::Point,
+	geometry::{Circle, LineSegment, Point, Rectangle},
 	pathfinder::{DiscoveredNodePtr, Pathfinder},
+	util::Windows,
 };
 
 #[allow(unused)]
@@ -17,6 +19,9 @@ macro_rules! log {
 extern "C" {
 	#[wasm_bindgen(js_namespace = console, js_name=warn)]
 	pub fn log(s: &str);
+
+	#[wasm_bindgen(js_namespace = ["dragRuler", "private"], js_name=terrainRulerWrapper)]
+	pub fn distance_with_terrain(a: Point, b: Point) -> f64;
 }
 
 #[wasm_bindgen]
@@ -74,6 +79,112 @@ impl From<JsPoint> for Point {
 	}
 }
 
+#[wasm_bindgen]
+extern "C" {
+	pub type JsTerrainInfo;
+	pub type JsTerrainObject;
+	pub type JsTerrainShape;
+
+	#[wasm_bindgen(method, getter)]
+	fn object(this: &JsTerrainInfo) -> JsTerrainObject;
+
+	#[wasm_bindgen(method, getter)]
+	fn shape(this: &JsTerrainInfo) -> JsTerrainShape;
+
+	#[wasm_bindgen(method, getter)]
+	fn x(this: &JsTerrainObject) -> f64;
+
+	#[wasm_bindgen(method, getter)]
+	fn y(this: &JsTerrainObject) -> f64;
+
+	#[wasm_bindgen(method, getter)]
+	fn width(this: &JsTerrainObject) -> f64;
+
+	#[wasm_bindgen(method, getter)]
+	fn height(this: &JsTerrainObject) -> f64;
+
+	#[wasm_bindgen(method, getter, js_name = "type")]
+	fn shape_type(this: &JsTerrainShape) -> u32;
+
+	#[wasm_bindgen(method, getter)]
+	fn x(this: &JsTerrainShape) -> f64;
+
+	#[wasm_bindgen(method, getter)]
+	fn y(this: &JsTerrainShape) -> f64;
+
+	#[wasm_bindgen(method, getter)]
+	fn radius(this: &JsTerrainShape) -> f64;
+
+	#[wasm_bindgen(method, getter)]
+	fn points(this: &JsTerrainShape) -> Vec<f64>;
+}
+
+impl JsTerrainObject {
+	fn to_bounding_rect(&self) -> Rectangle {
+		let left = self.x();
+		let top = self.y();
+		let right = left + self.width();
+		let bottom = top + self.height();
+		Rectangle::new(left, top, right, bottom)
+	}
+}
+
+impl JsTerrainShape {
+	fn to_segments(&self, x: f64, y: f64) -> Vec<LineSegment> {
+		let points = self.points();
+		assert!(points.len() % 2 == 0);
+		points
+			.chunks(2)
+			.map(|coordinates| Point::new(coordinates[0] + x, coordinates[1] + y))
+			.windows()
+			.map(|(p1, p2)| LineSegment::new(p1, p2))
+			.collect()
+	}
+
+	fn to_circle(&self, x: f64, y: f64) -> Circle {
+		let center = Point::new(self.x() + x, self.y() + y);
+		let radius = self.radius();
+		Circle { center, radius }
+	}
+}
+
+impl From<&JsTerrainInfo> for TerrainShape {
+	fn from(terrain: &JsTerrainInfo) -> Self {
+		let shape = terrain.shape();
+		let object = terrain.object();
+		let x = object.x();
+		let y = object.y();
+		match shape.shape_type() {
+			0 => TerrainShape::Polygon(shape.to_segments(x, y)),
+			2 => TerrainShape::Circle(shape.to_circle(x, y)),
+			_ => unimplemented!(),
+		}
+	}
+}
+
+#[derive(Debug, Clone)]
+pub enum TerrainShape {
+	Polygon(Vec<LineSegment>),
+	Circle(Circle),
+}
+
+#[derive(Debug, Clone)]
+pub struct Terrain {
+	pub shape: TerrainShape,
+	pub bounding_box: Rectangle,
+}
+
+impl From<&JsTerrainInfo> for Terrain {
+	fn from(terrain: &JsTerrainInfo) -> Self {
+		let bounding_box = terrain.object().to_bounding_rect();
+		let shape = terrain.into();
+		Self {
+			bounding_box,
+			shape,
+		}
+	}
+}
+
 #[wasm_bindgen]
 #[derive(Debug, Copy, Clone, PartialEq)]
 pub enum DoorState {
@@ -211,8 +322,7 @@ impl Wall {
 		c.iter_mut().for_each(|val| *val = val.round());
 		let height = if enable_height {
 			data.flags().wall_height().into()
-		}
-		else {
+		} else {
 			WallHeight::default()
 		};
 		Self::new(
@@ -228,13 +338,20 @@ impl Wall {
 
 #[allow(dead_code)]
 #[wasm_bindgen]
-pub fn initialize(js_walls: Vec<JsValue>, token_size: f64, token_elevation: f64, enable_height: bool) -> Pathfinder {
+pub fn initialize(
+	js_walls: Vec<JsValue>,
+	js_terrain: Vec<JsTerrainInfo>,
+	token_size: f64,
+	token_elevation: f64,
+	enable_height: bool,
+) -> Pathfinder {
 	let mut walls = Vec::with_capacity(js_walls.len());
 	for wall in js_walls {
 		let wall = JsWall::from(wall);
 		walls.push(Wall::from_js(&wall, enable_height));
 	}
-	Pathfinder::initialize(walls, token_size, token_elevation)
+	let terrain = js_terrain.iter().map(|terrain| terrain.into()).collect();
+	Pathfinder::initialize(walls, terrain, token_size, token_elevation)
 }
 
 #[allow(dead_code)]
@@ -262,6 +379,14 @@ pub fn debug_get_pathfinding_points(pathfinder: &Pathfinder) -> Array {
 		.collect()
 }
 
+#[allow(dead_code)]
+#[wasm_bindgen]
+pub fn sha1(input: &str) -> String {
+	let mut hasher = Sha1::new();
+	hasher.update(input);
+	format!("{:x}", hasher.finalize())
+}
+
 trait IteratePath {
 	fn iter_path(&self) -> PathIterator;
 }

rust/src/lib.rs

@@ -3,6 +3,7 @@ mod geometry;
 mod js_api;
 mod pathfinder;
 mod ptr_indexed_hash_set;
+mod util;
 
 use wasm_bindgen::prelude::*;
 

rust/src/pathfinder.rs

@@ -5,8 +5,8 @@ use wasm_bindgen::prelude::*;
 use rustc_hash::FxHashMap;
 
 use crate::{
-	geometry::{LineSegment, Point},
-	js_api::{Wall, WallSenseType},
+	geometry::{LineSegment, Point, Rectangle},
+	js_api::{distance_with_terrain, Terrain, TerrainShape, Wall, WallSenseType, log},
 	ptr_indexed_hash_set::PtrIndexedHashSet,
 };
 
@@ -84,7 +84,7 @@ impl NodeStorage {
 		self.regular_nodes.push(node);
 	}
 
-	fn initialize_edges(&mut self, node: &NodePtr, walls: &[LineSegment]) {
+	fn initialize_edges(&mut self, node: &NodePtr, walls: &[LineSegment], terrain: &[Rectangle]) {
 		if node.borrow().final_edge.is_none() {
 			let final_edge = self
 				.final_node
@@ -97,7 +97,11 @@ impl NodeStorage {
 				})
 				.map(|neighbor| Edge {
 					target: neighbor.clone(),
-					cost: node.borrow().point.distance_to(neighbor.borrow().point),
+					cost: Self::measure_distance(
+						node.borrow().point,
+						neighbor.borrow().point,
+						terrain,
+					),
 				});
 			node.borrow_mut().final_edge = Some(final_edge);
 		}
@@ -114,7 +118,8 @@ impl NodeStorage {
 			}
 			let neighbor_point = neighbor.borrow().point;
 			if !self.collides_with_wall(&LineSegment::new(point, neighbor_point), walls) {
-				let cost = point.distance_to(neighbor_point);
+				let cost =
+					Self::measure_distance(node.borrow().point, neighbor.borrow().point, terrain);
 				edges.push(Edge {
 					target: neighbor.clone(),
 					cost,
@@ -128,6 +133,15 @@ impl NodeStorage {
 		walls.iter().any(|wall| line.intersection(wall).is_some())
 	}
 
+	fn measure_distance(a: Point, b: Point, terrain: &[Rectangle]) -> f64 {
+		let segment = LineSegment::new(a, b);
+		if terrain.iter().any(|rect| segment.intersects_rect(rect)) {
+			distance_with_terrain(a, b)
+		} else {
+			a.distance_to(b)
+		}
+	}
+
 	pub fn cleanup_final_edges(&mut self) {
 		for node in &self.regular_nodes {
 			node.borrow_mut().final_edge = None;
@@ -145,35 +159,51 @@ pub struct Pathfinder {
 	pub nodes: NodeStorage,
 	#[wasm_bindgen(skip)]
 	pub walls: Vec<LineSegment>,
+	#[wasm_bindgen(skip)]
+	pub terrain: Vec<Rectangle>,
 }
 
 impl Pathfinder {
-	pub fn initialize<I>(walls: I, token_size: f64, token_elevation: f64) -> Self
-	where
-		I: IntoIterator<Item = Wall>,
-	{
+	pub fn initialize(
+		walls: Vec<Wall>,
+		terrain: Vec<Terrain>,
+		token_size: f64,
+		token_elevation: f64,
+	) -> Self {
+		log!("{:#?}", terrain);
 		let distance_from_walls = token_size / 2.0;
+
+		// TODO Place pathfinding nodes around terrain edges
+		let mut polygon_terrain = Vec::new();
+		let mut circle_terrain = Vec::new();
+
+		for terrain in &terrain {
+			match &terrain.shape {
+				TerrainShape::Polygon(polygon) => polygon_terrain.append(&mut polygon.clone()),
+				TerrainShape::Circle(circle) => circle_terrain.push(circle),
+			}
+		}
+
+		let mut walls = walls
+			.into_iter()
+			.filter(|wall| wall.move_type != WallSenseType::NONE)
+			.filter(|wall| !(wall.is_door() && wall.is_open()))
+			.filter(|wall| wall.height.contains(token_elevation))
+			.map(|wall| LineSegment::new(wall.p1, wall.p2))
+			.collect::<Vec<_>>();
+
+		// TODO Generate points around difficult terrain
 		let mut endpoints = FxHashMap::<Point, Vec<f64>>::default();
-		let mut line_segments = Vec::new();
-		for wall in walls {
-			if wall.move_type == WallSenseType::NONE {
-				continue;
-			}
-			if wall.is_door() && wall.is_open() {
-				continue;
-			}
-			if !wall.height.contains(token_elevation) {
-				continue;
-			}
-			let x_diff = wall.p2.x - wall.p1.x;
-			let y_diff = wall.p2.y - wall.p1.y;
+
+		for segments in walls.iter().chain(polygon_terrain.iter()) {
+			let x_diff = segments.p2.x - segments.p1.x;
+			let y_diff = segments.p2.y - segments.p1.y;
 			let p1_angle = y_diff.atan2(x_diff).rem_euclid(2.0 * PI);
 			let p2_angle = (p1_angle + PI).rem_euclid(2.0 * PI);
-			for (point, angle) in [(wall.p1, p1_angle), (wall.p2, p2_angle)] {
+			for (point, angle) in [(segments.p1, p1_angle), (segments.p2, p2_angle)] {
 				let angles = endpoints.entry(point).or_insert_with(Vec::new);
 				angles.push(angle);
 			}
-			line_segments.push(LineSegment::new(wall.p1, wall.p2));
 		}
 		endpoints
 			.values_mut()
@@ -196,19 +226,19 @@ impl Pathfinder {
 					point,
 					angle_between,
 					distance_from_walls,
-					&mut line_segments,
+					&mut walls,
 				));
 				nodes.push(calc_pathfinding_node(
 					point,
 					angle1 + 0.5 * PI,
 					distance_from_walls,
-					&mut line_segments,
+					&mut walls,
 				));
 				nodes.push(calc_pathfinding_node(
 					point,
 					angle2 - 0.5 * PI,
 					distance_from_walls,
-					&mut line_segments,
+					&mut walls,
 				));
 			}
 			let angle1 = angles.last().unwrap();
@@ -222,25 +252,46 @@ impl Pathfinder {
 				point,
 				angle_between,
 				distance_from_walls,
-				&mut line_segments,
+				&mut walls,
 			));
 			nodes.push(calc_pathfinding_node(
 				point,
 				angle1 + 0.5 * PI,
 				distance_from_walls,
-				&mut line_segments,
+				&mut walls,
 			));
 			nodes.push(calc_pathfinding_node(
 				point,
 				angle2 - 0.5 * PI,
 				distance_from_walls,
-				&mut line_segments,
+				&mut walls,
 			));
 		}
+
+		// TODO Check bounding box of circle terrain
+		for circle in circle_terrain {
+			let angle_step = f64::asin(token_size / 2.0 / circle.radius);
+			let mut angle = 0.0;
+			while angle < 2.0 * PI {
+				let point = Point {
+					x: circle.center.x + angle.cos() * circle.radius,
+					y: circle.center.y + angle.sin() * circle.radius,
+				};
+				nodes.push(calc_pathfinding_node(
+					point,
+					angle,
+					distance_from_walls,
+					&mut walls,
+				));
+				angle += angle_step;
+			}
+		}
+
 		// TODO Eliminating nodes close to each other may improve performance
 		Self {
 			nodes,
-			walls: line_segments,
+			walls,
+			terrain: terrain.iter().map(|terrain| terrain.bounding_box).collect(),
 		}
 	}
 
@@ -249,7 +300,7 @@ impl Pathfinder {
 		let mut nodes = self.nodes.clone();
 		nodes.final_node = Some(NodePtr::from(Node::new(from)));
 		let to_node = NodePtr::from(Node::new(to));
-		nodes.initialize_edges(&to_node, &self.walls);
+		nodes.initialize_edges(&to_node, &self.walls, &self.terrain);
 		let to = DiscoveredNode {
 			node: to_node,
 			cost: 0.0,
@@ -282,7 +333,7 @@ impl Pathfinder {
 				if previous_nodes.contains(neighbor) {
 					continue;
 				}
-				nodes.initialize_edges(neighbor, &self.walls);
+				nodes.initialize_edges(neighbor, &self.walls, &self.terrain);
 				// Add a flat 0.00001 cost per node to discurage creation of unnecessary waypoints
 				let cost = current_node.borrow().cost + edge.cost + 0.00001;
 				let discovered_neighbor = DiscoveredNode {
@@ -312,11 +363,11 @@ fn calc_pathfinding_node(
 	p: Point,
 	angle: f64,
 	distance_from_walls: f64,
-	line_segments: &mut Vec<LineSegment>,
+	walls: &mut Vec<LineSegment>,
 ) -> NodePtr {
 	let offset_x = angle.cos() * distance_from_walls;
 	let offset_y = angle.sin() * distance_from_walls;
-	line_segments.push(LineSegment::new(
+	walls.push(LineSegment::new(
 		p,
 		Point {
 			x: p.x + offset_x * 0.99,

rust/src/util.rs

@@ -0,0 +1,44 @@
+pub struct WindowIterator<I: Iterator> {
+	iterator: I,
+	previous: Option<I::Item>,
+}
+
+impl<I: Iterator> Iterator for WindowIterator<I>
+where
+	I::Item: Copy,
+{
+	type Item = (I::Item, I::Item);
+
+	fn next(&mut self) -> Option<Self::Item> {
+		if self.previous.is_none() {
+			self.previous = self.iterator.next();
+		}
+		let current = self.iterator.next();
+		if current.is_none() {
+			return None;
+		}
+		let current = current.unwrap();
+		let previous = self.previous.unwrap();
+		let result = (current, previous);
+		self.previous = Some(current);
+		Some(result)
+	}
+}
+
+pub trait Windows<T> {
+	fn windows(self) -> WindowIterator<Self>
+	where
+		Self: Sized + Iterator;
+}
+
+impl<I: Iterator> Windows<I> for I {
+	fn windows(self) -> WindowIterator<Self>
+	where
+		Self: Sized + Iterator,
+	{
+		WindowIterator {
+			iterator: self,
+			previous: None,
+		}
+	}
+}