From 548ec5f09a71b7615a57a52c8995c7594de72ade Mon Sep 17 00:00:00 2001
From: Mitchell McCaffrey <mitchemmc@gmail.com>
Date: Fri, 7 Aug 2020 12:55:16 +1000
Subject: [PATCH] Added grid snapping to map tokens

---
 src/components/map/Map.js      |  1 +
 src/components/map/MapToken.js | 24 ++++++++++++++++++++++++
 2 files changed, 25 insertions(+)

diff --git a/src/components/map/Map.js b/src/components/map/Map.js
index 2e7d854..fa0c28a 100644
--- a/src/components/map/Map.js
+++ b/src/components/map/Map.js
@@ -252,6 +252,7 @@ function Map({
             }
             mapState={mapState}
             fadeOnHover={selectedToolId === "drawing"}
+            map={map}
           />
         ))}
     </Group>
diff --git a/src/components/map/MapToken.js b/src/components/map/MapToken.js
index 54bd867..2156ba7 100644
--- a/src/components/map/MapToken.js
+++ b/src/components/map/MapToken.js
@@ -6,6 +6,7 @@ import useImage from "use-image";
 import useDataSource from "../../helpers/useDataSource";
 import useDebounce from "../../helpers/useDebounce";
 import usePrevious from "../../helpers/usePrevious";
+import * as Vector2 from "../../helpers/vector2";
 
 import AuthContext from "../../contexts/AuthContext";
 import MapInteractionContext from "../../contexts/MapInteractionContext";
@@ -15,6 +16,8 @@ import TokenLabel from "../token/TokenLabel";
 
 import { tokenSources, unknownSource } from "../../tokens";
 
+const snappingThreshold = 1 / 5;
+
 function MapToken({
   token,
   tokenState,
@@ -26,6 +29,7 @@ function MapToken({
   draggable,
   mapState,
   fadeOnHover,
+  map,
 }) {
   const { userId } = useContext(AuthContext);
   const {
@@ -74,6 +78,25 @@ function MapToken({
     onTokenDragStart(event);
   }
 
+  function handleDragMove(event) {
+    const tokenGroup = event.target;
+    // Snap to corners of grid
+    if (map.snapToGrid) {
+      const position = {
+        x: tokenGroup.x() + tokenGroup.width() / 2,
+        y: tokenGroup.y() + tokenGroup.height() / 2,
+      };
+      const gridSize = { x: mapWidth / map.gridX, y: mapHeight / map.gridY };
+      const gridSnap = Vector2.roundTo(position, gridSize);
+      const gridDistance = Vector2.length(Vector2.subtract(gridSnap, position));
+      const minGrid = Vector2.min(gridSize);
+      if (gridDistance < minGrid * snappingThreshold) {
+        tokenGroup.x(gridSnap.x - tokenGroup.width() / 2);
+        tokenGroup.y(gridSnap.y - tokenGroup.height() / 2);
+      }
+    }
+  }
+
   function handleDragEnd(event) {
     const tokenGroup = event.target;
 
@@ -192,6 +215,7 @@ function MapToken({
       onTap={handleClick}
       onDragEnd={handleDragEnd}
       onDragStart={handleDragStart}
+      onDragMove={handleDragMove}
       opacity={tokenOpacity}
       name={token && token.isVehicle ? "vehicle" : "token"}
       id={tokenState.id}