1 var d3_timer_queue = null,

     2     d3_timer_interval, // is an interval (or frame) active?

     3     d3_timer_timeout; // is a timeout active?

     4 

     5 // The timer will continue to fire until callback returns true.

     6 d3.timer = function(callback, delay, then) {

     7   var found = false,

     8       t0,

     9       t1 = d3_timer_queue;

    10 

    11   if (arguments.length < 3) {

    12     if (arguments.length < 2) delay = 0;

    13     else if (!isFinite(delay)) return;

    14     then = Date.now();

    15   }

    16 

    17   // See if the callback's already in the queue.

    18   while (t1) {

    19     if (t1.callback === callback) {

    20       t1.then = then;

    21       t1.delay = delay;

    22       found = true;

    23       break;

    24     }

    25     t0 = t1;

    26     t1 = t1.next;

    27   }

    28 

    29   // Otherwise, add the callback to the queue.

    30   if (!found) d3_timer_queue = {

    31     callback: callback,

    32     then: then,

    33     delay: delay,

    34     next: d3_timer_queue

    35   };

    36 

    37   // Start animatin'!

    38   if (!d3_timer_interval) {

    39     d3_timer_timeout = clearTimeout(d3_timer_timeout);

    40     d3_timer_interval = 1;

    41     d3_timer_frame(d3_timer_step);

    42   }

    43 }

    44 

    45 function d3_timer_step() {

    46   var elapsed,

    47       now = Date.now(),

    48       t1 = d3_timer_queue;

    49 

    50   while (t1) {

    51     elapsed = now - t1.then;

    52     if (elapsed >= t1.delay) t1.flush = t1.callback(elapsed);

    53     t1 = t1.next;

    54   }

    55 

    56   var delay = d3_timer_flush() - now;

    57   if (delay > 24) {

    58     if (isFinite(delay)) {

    59       clearTimeout(d3_timer_timeout);

    60       d3_timer_timeout = setTimeout(d3_timer_step, delay);

    61     }

    62     d3_timer_interval = 0;

    63   } else {

    64     d3_timer_interval = 1;

    65     d3_timer_frame(d3_timer_step);

    66   }

    67 }

    68 

    69 d3.timer.flush = function() {

    70   var elapsed,

    71       now = Date.now(),

    72       t1 = d3_timer_queue;

    73 

    74   while (t1) {

    75     elapsed = now - t1.then;

    76     if (!t1.delay) t1.flush = t1.callback(elapsed);

    77     t1 = t1.next;

    78   }

    79 

    80   d3_timer_flush();

    81 };

    82 

    83 // Flush after callbacks, to avoid concurrent queue modification.

    84 function d3_timer_flush() {

    85   var t0 = null,

    86       t1 = d3_timer_queue,

    87       then = Infinity;

    88   while (t1) {

    89     if (t1.flush) {

    90       t1 = t0 ? t0.next = t1.next : d3_timer_queue = t1.next;

    91     } else {

    92       then = Math.min(then, t1.then + t1.delay);

    93       t1 = (t0 = t1).next;

    94     }

    95   }

    96   return then;

    97 }

    98 

    99 var d3_timer_frame = window.requestAnimationFrame

   100     || window.webkitRequestAnimationFrame

   101     || window.mozRequestAnimationFrame

   102     || window.oRequestAnimationFrame

   103     || window.msRequestAnimationFrame

   104     || function(callback) { setTimeout(callback, 17); };