[webkit-dev] Proposed Timer API

Maciej Stachowiak mjs at apple.com
Fri Oct 3 13:57:47 PDT 2008

On Oct 3, 2008, at 11:15 AM, Geoffrey Garen wrote:

> Hi Chris.
>> I really like the idea of a Timer object. It would allow you to
>> separate creation from starting, allows you to pause and add other
>> API's to the interface. Can the constructor be used to simplify the
>> creation:
>>    var t = new Timer(0, false, function() { ...});
>> which would start the timer immediately, as in your example.
> I think Maciej has made a convincing case that "new Timer" is a bit  
> too coy about the fact that the timer is actually starting.
>> Or you could do:
>>    var t = new Timer(function() { ... });
>>    ...
>>    t.startOneShot(1.76);
> I like your suggestion of adding "startOneShot" (and  
> "startRepeating"?) to the API. I think it would improve clarity over  
> a bool parameter specifying whether the timer repeats.
> To create a Timer that isn't scheduled to fire:
> new Timer(...)
> To create a Timer that is scheduled to fire:
> new Timer(...).startOneShot(...)
> new Timer(...).startRepeating(...)

It would be pretty unusual for a method like startOneShot or  
startRepeating to return a value. I'm not sure if you indended that;  
if not

> Or, if we don't like constructors:
> createTimer(...).startOneShot(...)
> createTimer(...).startRepeating(...)

We could rename the restart() method to start() (with the same  
semantics, or also taking a bool) and have both createTimer() and  
startTimer() if we think this use case is very important. I don't  
think the need for unstarted timers is very high. However, here's yet  
another tricksy way to achieve the same thing:

var tSpec = [0, false, function() {...});
var t = startTimer.apply(window, tSpec);

I think setting up a Timer with the intent of not only starting it but  
defining the timing parameters is extra useless, since then all it  
represents is a function.


>> And you could easily add animation or media API's for  
>> synchronization:
>>    var t = new Timer(1.76, function() { ... }); // when the timer is
>> triggered, it will run for 1.76 seconds
>>    var transition = window.getTransitionForElement(element, "left");
>>    transition.trigger(t);
>>    ...
>>    element.style.left = "100px";
>> This would cause the timer to start when the left transition starts
>> and fire its event 1.76 seconds later.
> This would be really cool!
> Geoff

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