Canvas shadows should not be optional

http://www.w3.org/html/wg/html5/#shadows says:

"Support for shadows is optional. When they are supported, then, when 
shadows are drawn, they must be rendered as follows:"

Suggested replacement text:

"When shadows are drawn, they must be rendered as follows:"


There are already two released canvas implementations (in Safari 2/3, 
Konqueror 4) that interoperably implement shadows as specified (except 
for some minor bugs). There is also a patch to implement them in Gecko 
(though it won't be in Firefox 3).

(http://philip.html5.org/demos/canvas/shadows/various.html should look 
like http://philip.html5.org/demos/canvas/shadows/expected.png in 
browsers that implement shadows correctly.)

Some existing content already makes use of shadow rendering, e.g. 
http://media.liquidx.net/js/plotkit-tests/sweet.html and 
http://www.ditchnet.org/scribble/curves.html

I'm not aware of reasons why any canvas implementation would be 
incapable of implementing shadows and would require the spec to not 
require it.

So, for interoperability and platform consistency, the feature should 
not be optional. Since it's already used (indicating that it's a useful 
feature) and implemented (and fairly easy to add into other 
implementations), it seems best to require it instead of dropping it.

-- 
Philip Taylor
pjt47@cam.ac.uk

Received on Saturday, 26 April 2008 16:14:44 UTC