[whatwg] Canvas Shadows - Unnecessary Barrier to Entry

Philip Taylor excors+whatwg at gmail.com
Sat Mar 28 06:29:32 PDT 2009

On Fri, Mar 27, 2009 at 11:22 PM, Charles Pritchard <chuck at jumis.com> wrote:
> [...]
> We've been working on Javascript / Canvas projects for two years now.
> We're in the process of releasing full implementations targeting the Common
> Runtime Language,
> Java AWT, ActionScript and DCOM.
> I'm sure you can all recognize, that these components have their own vector
> APIs,
> and that we're only sending requests through as a proxy.
> While we can implement everything, even the non-zero winding rule,
> there one part of the specification that's absolutely rotten. And that's the
> #shadows section.
> I love a shadow, I love a good looking UI, but most of these APIs do not
> have shadow
> support for shapes.

Do the APIs not provide enough features so you can implement shadows
yourself? e.g. Firefox uses Cairo which doesn't have any native
support for shadows; but it can draw shapes onto an alpha-only
surface, manually blur the pixels (if you can implement getImageData
then I assume you must already have access to the raw pixels and can
do the blurring efficiently), then draw the shape again, and composite
everything appropriately, which results in a correct shadow
implementation. I don't see what makes this fundamentally harder than
implementing all the other required canvas features.

> [...]

Philip Taylor
excors at gmail.com

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