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Re: throw or not when sw or sh is zero in drawImage(img, 0, 0, sw, wh, ...) (WHATWG r7589)

From: Rik Cabanier <cabanier@gmail.com>
Date: Thu, 21 Mar 2013 21:28:13 -0700
Message-ID: <CAGN7qDD4s6fm6TwhOwOOdohaA3fcZN8Us2VH+8qTcGqjYrjH-g@mail.gmail.com>
To: "Kang-Hao (Kenny) Lu" <kanghaol@oupeng.com>
Cc: W3C Canvas Spec <public-canvas-api@w3.org>, HTML-related tests <public-html-testsuite@w3.org>, Tietao Wang <tietaow@opera.com>
Sorry, I was confused about the particular API call you were referring to.
Also, are you a web developer or do you work on a browser? (I thought you
were a developer)

There is indeed a trend to be more forgiving in the user facing APIs.
If Firefox also moves to not throwing, I would be happy to change the
Canvas spec.

We should pick up the conversation on the WhatWG mailing list again so we
can get close this issue. Last I heard, people were reluctant to change
since there were already 2 shipping implementations and I was almost ready
to integrate a WebKit patch to fix the behavior.

Rik

On Thu, Mar 21, 2013 at 9:02 PM, Kang-Hao (Kenny) Lu <kanghaol@oupeng.com>wrote:

> (13/03/22 3:45), Rik Cabanier wrote:
> > The spec was changed at the last minute by the WhatWG and it was actually
> > done by accident. (Cameron did a global replace for WebIDL.)
>
> How would doing a global replace for WebIDL change the spec prose? Just
> curious.
>
> > The W3C version reversed that change since the change was unintentional
> and
> > there were already 2 independent implementations. Ian decided that the
> new
> > prose made more sense and just left it in.
>
> roc seemed to indicate that he has a patch for removing these errors[1]
> (although I haven't found the relevant Bugzilla bug) so "having 2
> independent implementations" doesn't seem like a stable assertion.
>
> Should we raise a discussion on the WHATWG list if we intend to keep the
> current prose in the W3C version as it is?
>
> [1] http://lists.w3.org/Archives/Public/public-whatwg-archive/2013Mar/0020
>
> > As a developer you should try to catch the exception since both Firefox
> and
> > IE will throw. This will make your code work everywhere.
>
> Not sure what you mean here. This doesn't look like an argument against
> the backwards-compat argument. As UA developers, we don't want to do
> unnecessary Web evangelism. As Web developer, I'd say using try and
> catch in JS is not as common as in other languages.
>
> > If those browser change their behavior, we will update the spec
> > accordingly (but you will still have to account for old browsers)
>
> A UA needs to account for old contents.
>
> >> 2. Compatibility
> >>
> >> Currently only WebKit implements the WHATWG behavior (not throwing).
> >> However, it seems very likely that this part of the Web (the WebKit Web
> >> :( ) is already depending on drawImage not throwing. Google
> >> "IndexSizeError" gives [3][4][5], and I bet there are much more. Also,
> >> it is known that getting the Android WebView to change is hard, and
> >> therefore not throwing seems like the way to converge.
> >>
> >>
> >> Anyway, the baseline is that we shouldn't have a difference between the
> >> two specs.
> >>
> >> [3] https://github.com/Animatron/player/pull/70
> >> [4] https://github.com/aduros/flambe/issues/55
> >> [5] http://groups.google.com/group/melonjs/msg/571b36150fd2760b
>
> Cheers,
> Kenny
> --
> Web Specialist, Opera Sphinx Game Force, Oupeng Browser, Beijing
> Try Oupeng: http://www.oupeng.com/
>
Received on Friday, 22 March 2013 04:28:42 GMT

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