[Webkit-unassigned] [Bug 27292] Improve handling of <canvas> path operations on an empty path.

[bugzilla-daemon at webkit.org]

https://bugs.webkit.org/show_bug.cgi?id=27292





--- Comment #5 from Dean McNamee <deanm at chromium.org>  2009-07-15 03:20:01 PDT ---
Discussion of the cairo behavior is here:

http://lists.freedesktop.org/archives/cairo/2008-June/014262.html

I guess the reason cairo behaves like it does, is because it still wants to
emit a curve.  I think the current behavior for browser should be to not emit
anything, and just do the moveTo.  I will follow up with Mozilla.

(In reply to comment #4)
> (In reply to comment #3)
> > Differs from Firefox, looks like the control point vs endpoint, but I really
> > don't see how control point could ever make any sense.  I'll look at their code
> > today, and maybe file a bug with them.
> > 
> > (In reply to comment #2)
> > > (From update of attachment 32772 [details] [details] [details])
> > > In general this seems okay to me -- how does the output compare to firefox?
> 
> Ok, so Firefox just passes this directly to cairo:
> 
> 162 void
> 163 gfxContext::LineTo(const gfxPoint& pt)
> 164 {
> 165     cairo_line_to(mCairo, pt.x, pt.y);
> 166 }
> 
> And Cairo has the control point behavior:
> 
> http://cairographics.org/manual/cairo-paths.html#cairo-curve-to
> 
> If there is no current point before the call to cairo_curve_to() this function
> will behave as if preceded by a call to cairo_move_to(cr, x1, y1).
> 
> I think they should cairo_has_current_point() and cairo_move_to the endpoints
> if not.  I'll file a bug with Mozilla.  I wonder why Cairo has this behavior.

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