[whatwg] Compatibility problems with HTML5 Canvas spec.

Ian Hickson ian at hixie.ch
Thu Jan 31 21:23:37 PST 2008

On Mon, 24 Sep 2007, Oliver Hunt wrote:
> The first problem is the repeated drawing of old rects, this is due to 
> the context path not being cleared by draw rect and fill rect which is 
> the behaviour present in Safari 2 and Firefox 2.  While I've discussed 
> the issue with Hixie in the past (and to an extent agree with him) the 
> Firefox 3 nightlies do not appear to have adopted this behaviour, 
> leaving us in a position where we have to choose between compatibility 
> and compliance which is awkward.

Firefox 3 has now fixed this.

> The second problem is that the rules for drawing rects/adding rects to 
> the path require us to throw an exception on negative width/height, once 
> again Firefox 3 does not match this behaviour, putting us in a position 
> where we need to choose between compatibility and compliance.  In this 
> case however it is relatively easy to make the argument that an 
> exception should _not_ be thrown, as it means webapp developers either 
> need to litter their code with exception handlers or add significant 
> logic to ensure that their apps do not unexpectedly terminate.

Fixed in the spec (defined by the operations x+w and y+h).

Ian Hickson               U+1047E                )\._.,--....,'``.    fL
http://ln.hixie.ch/       U+263A                /,   _.. \   _\  ;`._ ,.
Things that are impossible just take longer.   `._.-(,_..'--(,_..'`-.;.'

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