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Re: [whatwg] High-density canvases

From: Robert O'Callahan <robert@ocallahan.org>
Date: Thu, 26 Jun 2014 10:13:34 +1200
Message-ID: <CAOp6jLZU1k6VwYdcRN_PVD-gdmjN6fFA_BHasd=5AmpBGaVrow@mail.gmail.com>
To: Justin Novosad <junov@google.com>
Cc: Rik Cabanier <cabanier@gmail.com>, Kenneth Russell <kbr@google.com>, Stephen White <senorblanco@chromium.org>, WHAT Working Group <whatwg@whatwg.org>, Dean Jackson <dino@apple.com>, Ian Hickson <ian@hixie.ch>
On Thu, Jun 26, 2014 at 10:10 AM, Robert O'Callahan <robert@ocallahan.org>

> On Thu, Jun 26, 2014 at 2:49 AM, Justin Novosad <junov@google.com> wrote:
>> I was wondering if there is anything we can do with this feature to
>> prevent
>> web apps from creating layout feedback loops.  What I mean is that if the
>> event listener for renderedsizechange changes the layout of the page in a
>> way that does not preserve renderedPixelWidth/Height, we can get into a
>> lot
>> of trouble. Even if the resizing arithmetic in the event listener is
>> sound,
>> if the rounding logic does not match exactly what the browser does,
>> fractional scales may cause instabilities.
>> The main source of of the problem is that intrinsic size affects CSS size
>> when width or height are set to 'auto', which is the default.  Some ideas
>> that come to mind for breaking the feedback loop:
>> 1) renderedPixelWidth/Height return the intrinsic size when CSS
>> width/height are set to 'auto'
>> 2) renderedPixelWidth/Height do not change when CSS width/height are set
>> to
>> 'auto'
> We could do this and I think it would work. It's arguable whether the
> complexity is justified, but I'd be OK with doing it.

To clarify, I think a version of option #1 would be the best way to go.
renderedPixelWidth would return the current canvas buffer width when the
canvas element's CSS specified value for 'width' is 'auto', and similar for

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Received on Wednesday, 25 June 2014 22:14:00 UTC

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