ddd

client/input/gesture-coordinator.js

@@ -0,0 +1,47 @@
+(function(root,factory){
+  const api=factory();
+  if(typeof module==='object'&&module.exports)module.exports=api;
+  root.BendGestureCoordinator=api;
+})(typeof globalThis!=='undefined'?globalThis:this,function(){
+  'use strict';
+
+  const DEFAULT_PRECEDENCE=Object.freeze({
+    wheel:10,
+    pan:20,
+    pinch:30,
+    reaction:40,
+    minimap:50,
+    draw:60,
+    dialog:70
+  });
+
+  function createGestureCoordinator(precedence=DEFAULT_PRECEDENCE){
+    const owners=new Map(),listeners=new Set();let revision=0;
+    const priority=owner=>Number(precedence[owner])||0;
+    const snapshot=()=>Object.freeze({revision,owners:Object.freeze(Object.fromEntries(owners))});
+    const notify=(change)=>{revision++;const state=snapshot();for(const listener of listeners)listener(state,change)};
+    const claim=(pointerId,owner,{replace=false}={})=>{
+      if(pointerId==null||!owner)return false;const key=String(pointerId),next=String(owner),current=owners.get(key);
+      if(current===next)return true;
+      if(current&&!replace&&priority(next)<=priority(current))return false;
+      owners.set(key,next);notify(Object.freeze({type:current?'transfer':'claim',pointerId:key,owner:next,previous:current||null}));return true;
+    };
+    const release=(pointerId,owner=null,reason='complete')=>{
+      if(pointerId==null)return false;const key=String(pointerId),current=owners.get(key);
+      if(!current||owner!=null&&current!==String(owner))return false;
+      owners.delete(key);notify(Object.freeze({type:'release',pointerId:key,owner:current,reason}));return true;
+    };
+    const cancelAll=(reason='cancelled')=>{for(const[key,owner]of[...owners]){owners.delete(key);notify(Object.freeze({type:'release',pointerId:key,owner,reason}))}};
+    return Object.freeze({
+      claim,
+      release,
+      cancelAll,
+      owner:pointerId=>pointerId==null?null:owners.get(String(pointerId))||null,
+      owns:(pointerId,owner)=>owners.get(String(pointerId))===String(owner),
+      snapshot,
+      subscribe(listener){if(typeof listener!=='function')throw new TypeError('Listener must be a function');listeners.add(listener);return()=>listeners.delete(listener)}
+    });
+  }
+
+  return Object.freeze({DEFAULT_PRECEDENCE,createGestureCoordinator});
+});