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Re: Javascript properties and Houdini types

From: Kevin Doughty <socallednonflipped@gmail.com>
Date: Mon, 30 Nov 2015 15:13:33 -0500
Message-ID: <CAAbwtRx=JXuCy=fAdX3G5FBLAdNzYafGKsAYcHA2z8pw7whAVQ@mail.gmail.com>
To: public-fx@w3.org, public-houdini@w3.org
// Perhaps a declaration with minimal animation settings could look
something like this:
var myObject = { ivar: Math.PI * 2 };
Object.defineProperty(myObject, 'arbitrary', {
  get: function() { return ivar; },
  set: function(value) { ivar = value; },
  enumerable: true,
  configurable: true,
  transition: {
    syntax: '<number>',
    duration: 1.0, // or '1.0s' or 1000 or whatever
    // more fun animation options here

// Then somehow there would need to be an easy way to get an object with
animation values composited:
var myPresentationObject = Object.presentationLayer(myObject);

On Sun, Nov 29, 2015 at 7:25 PM, Kevin Doughty <socallednonflipped@gmail.com
> wrote:

> I would like to animate arbitrary properties of Javascript objects. I find
> Houdini Properties and Values to be really compelling, and would like to be
> able to trigger animations of non-CSS properties using something similar to
> the apply function. I envision Object.defineProperty as a possible place to
> declare transitions of Javascript property values. I saw one comment in an
> early Houdini draft that suggested it could be a place to trigger CSS
> animations, and I hope this is revisited.
> I have a Javascript framework loosely based on Core Animation. It is meant
> for use with code that depends on DOM diffing with a render function. The
> primary difference of other animation techniques is the easy access to
> specified vs. animated values. I achieve this by making copies of the
> Javascript object whose properties are to be interpolated, and compositing
> the values onto the new object. Then the render function is bound to the
> copy, so the same code is provided animated values. This is very similar to
> behavior of Core Animation model and presentation layers. Core Animation
> has a third private layer, the render tree, which I do not consider because
> of Javascript’s single threaded nature.
> One problem I fear is the community making decisions about the future of
> Javascript is concerned with language and syntax, and does not consider
> animation. Conversely, the community making decisions about the future of
> animation are focused solely on CSS and SVG properties, but they ignore the
> numerous frameworks that use DOM diffing and animate by rAF with a render
> function.
> This gap needs to be bridged. Along with those DOM diffing frameworks,
> there are plenty of other uses, for example animating canvas and webGL
> (vertices at least) with a unified animation API.
> My goal is discrete app state. This is partially accomplished by relative
> additive animation. Along with this, animations that rely on imperative
> function calls in completion handlers must be avoided. The reason for this
> is to prevent indeterminate state between animation start and stop. When
> interrupting, all possibilities must be known and reasoned about, which is
> undesirable. Thus the need to do everything at once, at the start of an
> animation.
> I will give two common examples of where completion handlers are typically
> used but could be avoided. The first is simpler, fading out an element but
> not removing it, merely setting display:none. This is a place where many
> might make the lazy choice to depend on a callback. Web Animations in some
> form or other would allow for a constant animation on the property display
> to animate from “block” to “block”, which would bring the element back for
> the duration of an opacity fade.
> The more complicated example is animating insertion and removal children.
> It would require a new Houdini Properties and Values type. I see you have
> arrays, which seem to be for ordering transform functions. I would want
> arrays for animating arrays of number types, like points on a canvas or
> webGL vertices. But I propose a new animatable type, for mathematical sets.
> Because they are unordered, their contents would not be individually
> interpolatable like arrays. Instead, they would discretely animate their
> contents from one state to another, behaving like Web-Animations
> non-numeric values.
> If you animate children as sets then you can avoid completion handers. Of
> course the animation is additive and relative, you should know I would be
> advocating this by now. The only requirement is that elements must be
> sortable, with the limitation that data sets must be reasonably small.
> Take for instance animating form children A-B-C-D to A-B-D. Element C will
> be removed. Old minus new, A-B-C-D minus A-B-D leaves C. Then when added
> back to the underlying, non-animated value of A-B-D, results in A-B-D-C
> which must then be sorted. An opacity animation would fade out while the
> children set animation would keep the child being removed in place until
> the animation is completed. Bringing an element back from A-B-D to A-B-C-D
> does not require any work. Subtraction results in an empty set. The element
> is added instantly and that is all you need to do, other than run an
> opacity fade or other animation. Like the display:none example this avoids
> race conditions and corruption of state entirely, albeit in simple cases.
> I have some example code. The first shows what I’ve just described, in
> three columns. On the left are buttons to trigger insertion and removal.
> The middle column shows the display:none technique. The right column shows
> removal of children.
> http://codepen.io/kvndy/pen/avedLe/?editors=001
> The second is a case for interpolating arrays of numbers for canvas
> drawing. The render function is provided with an array of numbers with the
> animations already composited. This is opposed to animation techniques in
> frameworks like React which require manual conversion / function calls to
> get the animated value. They may argue that those calls are trivial, to
> which I would reply that DOM manipulation is also trivial. If they go
> through the trouble of making a declarative render function then animated
> values should be provided automatically, otherwise their render function is
> not so declarative. Thus the render function here just needs to loop
> through points and plot them.
> http://codepen.io/kvndy/pen/KdrWKN?editors=001
> I make arbitrary decisions in my animation code to provide composited
> presentation values to the render function, which would need to be a
> decision made by authors of Javascript frameworks. But having a way to
> automatically composite values from animations from one Javascript object
> into another, easily accessed and using the same animation API that backs
> CSS, would be a revolution for the web.
> Thanks for considering this proposal.
Received on Monday, 30 November 2015 20:14:05 UTC

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