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Re: [whatwg] Canvas-Only Document Type

From: Silvia Pfeiffer <silviapfeiffer1@gmail.com>
Date: Tue, 8 Jul 2014 08:54:18 +1000
Message-ID: <CAHp8n2n4ErvTX81HX7Qwh8-NsWtmbuFLTKoj_oTfx+GEUYZVSg@mail.gmail.com>
To: "Brian M. Blakely" <anewpage.media@gmail.com>
Cc: "whatwg@lists.whatwg.org" <whatwg@lists.whatwg.org>, Ashley Gullen <ashley@scirra.com>
Has anyone considered the accessibility implications of this? IIUC
accessibility for canvas is provided through extra dom elements. So,
this would defeat that purpose.


On Tue, Jul 8, 2014 at 8:39 AM, Brian M. Blakely
<anewpage.media@gmail.com> wrote:
> Hi Ashley,
> With the budding of Canvas 2D and WebGL UI frameworks, I believe that, in a couple years' time, the role of CSS in the cases I described will diminish drastically. A lot of this was kind of waiting for Apple to give the OK before people began committing their hearts to WebGL.
>> On Jul 7, 2014, at 5:17 PM, Ashley Gullen <ashley@scirra.com> wrote:
>> Having developed a major HTML5 game engine, and given this appears to be aimed at a gaming use case, I feel qualified to offer my opinion: I'm not sure this is a good idea.
>> Despite being 99% canvas and javascript, we use CSS to implement some useful scaling modes (like letterbox fullscreen). We also use the DOM for many useful features, such as form controls, divs, Twitter or Facebook buttons and so on, which are positioned over the canvas. In particular text inputs are useful for things like name entry or logins even for games, and are typically difficult and error-prone to reimplement in only canvas and javascript.
>> Is there any evidence that such a mode would actually improve performance? Are there benchmarks indicating the existence of a DOM, even if inert, harms performance in any way?
>> Ashley Gullen
>> Scirra.com
>>> On 7 July 2014 21:35, Brian Blakely <anewpage.media@gmail.com> wrote:
>>> Floating a concept for a document mode which eschews CSS and the DOM
>>> to enable a more jank-free Canvas surface.
>>> Depending on how this allows for optimization, might be used well for
>>> games, VR, wearables, and ultra-portable or high-performance apps.
>>> Probably most beneficial to memory usage and first paint time.  Would
>>> appreciate if some vendor engineers who might be reading could chime
>>> in on this point.
>>> Strawman:
>>> Document only contains <!doctype canvas-[2d|3d]> and script elements.
>>> Everything else is ignored.  "document" object is gone.
>>> A Canvas drawing surface consumes the entire viewport.  It always has
>>> an opaque backing store, same as specifying getContext('2d', { alpha:
>>> false }).
>>> UA provides:
>>> * A host object representing surface's CanvasRenderingContext2D or
>>> WebGLRenderingContext (depending on specified doctype).
>>> * In lieu of DOM, an API for creating offscreen canvases (actually,
>>> this abstraction should probably exist anyway).  This might live on
>>> the Context host obj, which may open a beneficial performance
>>> relationship between onscreen canvas and offscreen "children".
Received on Monday, 7 July 2014 22:55:02 UTC

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