Insert new tasks on the end.

This is a partial fix to d3#1245 whereby timer tasks are now invoked in the order
in which they were registered, rather than in the reverse order. However, a
better fix remains, which is to invoke tasks in the order of their start time
rather than their registration time.

d3.js

@@ -1796,7 +1796,7 @@ d3 = function() {
   }
   d3.csv = d3_dsv(",", "text/csv");
   d3.tsv = d3_dsv("	", "text/tab-separated-values");
-  var d3_timer_id = 0, d3_timer_byId = {}, d3_timer_queue = null, d3_timer_interval, d3_timer_timeout;
+  var d3_timer_id = 0, d3_timer_byId = {}, d3_timer_queueHead, d3_timer_queueTail, d3_timer_interval, d3_timer_timeout;
   d3.timer = function(callback, delay, then) {
     if (arguments.length < 3) {
       if (arguments.length < 2) delay = 0; else if (!isFinite(delay)) return;
@@ -1806,20 +1806,24 @@ d3 = function() {
     if (timer && timer.callback === callback) {
       timer.then = then;
       timer.delay = delay;
-    } else d3_timer_byId[callback.id = ++d3_timer_id] = d3_timer_queue = {
-      callback: callback,
-      then: then,
-      delay: delay,
-      next: d3_timer_queue
-    };
+    } else {
+      d3_timer_byId[callback.id = ++d3_timer_id] = timer = {
+        callback: callback,
+        then: then,
+        delay: delay,
+        next: null
+      };
+      if (d3_timer_queueTail) d3_timer_queueTail.next = timer; else d3_timer_queueHead = timer;
+      d3_timer_queueTail = timer;
+    }
     if (!d3_timer_interval) {
       d3_timer_timeout = clearTimeout(d3_timer_timeout);
       d3_timer_interval = 1;
       d3_timer_frame(d3_timer_step);
     }
   };
   function d3_timer_step() {
-    var elapsed, now = Date.now(), t1 = d3_timer_queue;
+    var elapsed, now = Date.now(), t1 = d3_timer_queueHead;
     while (t1) {
       elapsed = now - t1.then;
       if (elapsed >= t1.delay) t1.flush = t1.callback(elapsed);
@@ -1838,7 +1842,7 @@ d3 = function() {
     }
   }
   d3.timer.flush = function() {
-    var elapsed, now = Date.now(), t1 = d3_timer_queue;
+    var elapsed, now = Date.now(), t1 = d3_timer_queueHead;
     while (t1) {
       elapsed = now - t1.then;
       if (!t1.delay) t1.flush = t1.callback(elapsed);
@@ -1847,16 +1851,17 @@ d3 = function() {
     d3_timer_flush();
   };
   function d3_timer_flush() {
-    var t0 = null, t1 = d3_timer_queue, then = Infinity;
+    var t0, t1 = d3_timer_queueHead, then = Infinity;
     while (t1) {
       if (t1.flush) {
         delete d3_timer_byId[t1.callback.id];
-        t1 = t0 ? t0.next = t1.next : d3_timer_queue = t1.next;
+        t1 = t0 ? t0.next = t1.next : d3_timer_queueHead = t1.next;
       } else {
         then = Math.min(then, t1.then + t1.delay);
         t1 = (t0 = t1).next;
       }
     }
+    d3_timer_queueTail = t0;
     return then;
   }
   var d3_timer_frame = d3_window.requestAnimationFrame || d3_window.webkitRequestAnimationFrame || d3_window.mozRequestAnimationFrame || d3_window.oRequestAnimationFrame || d3_window.msRequestAnimationFrame || function(callback) {

src/event/timer.js

@@ -2,7 +2,8 @@ import "../core/document";
 
 var d3_timer_id = 0,
     d3_timer_byId = {},
-    d3_timer_queue = null,
+    d3_timer_queueHead,
+    d3_timer_queueTail,
     d3_timer_interval, // is an interval (or frame) active?
     d3_timer_timeout; // is a timeout active?
 
@@ -21,13 +22,18 @@ d3.timer = function(callback, delay, then) {
     timer.delay = delay;
   }
 
-  // Otherwise, add the callback to the queue.
-  else d3_timer_byId[callback.id = ++d3_timer_id] = d3_timer_queue = {
-    callback: callback,
-    then: then,
-    delay: delay,
-    next: d3_timer_queue
-  };
+  // Otherwise, add the callback to the tail of the queue.
+  else {
+    d3_timer_byId[callback.id = ++d3_timer_id] = timer = {
+      callback: callback,
+      then: then,
+      delay: delay,
+      next: null
+    };
+    if (d3_timer_queueTail) d3_timer_queueTail.next = timer;
+    else d3_timer_queueHead = timer;
+    d3_timer_queueTail = timer;
+  }
 
   // Start animatin'!
   if (!d3_timer_interval) {
@@ -40,7 +46,7 @@ d3.timer = function(callback, delay, then) {
 function d3_timer_step() {
   var elapsed,
       now = Date.now(),
-      t1 = d3_timer_queue;
+      t1 = d3_timer_queueHead;
 
   while (t1) {
     elapsed = now - t1.then;
@@ -64,7 +70,7 @@ function d3_timer_step() {
 d3.timer.flush = function() {
   var elapsed,
       now = Date.now(),
-      t1 = d3_timer_queue;
+      t1 = d3_timer_queueHead;
 
   while (t1) {
     elapsed = now - t1.then;
@@ -77,18 +83,19 @@ d3.timer.flush = function() {
 
 // Flush after callbacks to avoid concurrent queue modification.
 function d3_timer_flush() {
-  var t0 = null,
-      t1 = d3_timer_queue,
+  var t0,
+      t1 = d3_timer_queueHead,
       then = Infinity;
   while (t1) {
     if (t1.flush) {
       delete d3_timer_byId[t1.callback.id];
-      t1 = t0 ? t0.next = t1.next : d3_timer_queue = t1.next;
+      t1 = t0 ? t0.next = t1.next : d3_timer_queueHead = t1.next;
     } else {
       then = Math.min(then, t1.then + t1.delay);
       t1 = (t0 = t1).next;
     }
   }
+  d3_timer_queueTail = t0;
   return then;
 }
 

test/event/timer-test.js

@@ -32,6 +32,20 @@ suite.addBatch({
       "calls every 17 ms": function(info) {
         assert.inDelta(info.stop - info.start, 17 * 3, 20);
       }
+    },
+
+    "with multiple registered tasks": {
+      topic: function(timer) {
+        var callback = this.callback,
+            results = [];
+        timer(function() { results.push("A"); return true; });
+        timer(function() { results.push("B"); return true; });
+        timer(function() { results.push("C"); return true; });
+        timer(function() { callback(null, results); return true; })
+      },
+      "invokes tasks in the order they were registered": function(results) {
+        assert.deepEqual(results, ["A", "B", "C"]);
+      }
     }
   }
 });