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Canvas arcTo comments

From: Philip Taylor <pjt47@cam.ac.uk>
Date: Sun, 27 Apr 2008 16:57:09 +0100
Message-ID: <4814A255.8060706@cam.ac.uk>
To: HTML WG <public-html@w3.org>

The behaviour of arcTo is undefined for radius=0. (In particular, "let 
The Arc be the shortest arc given by circumference of the circle that 
has radius radius, and that has one point tangent to [some line], and 
that has a different point tangent to [some other line]" is impossible 
to satisfy, since there aren't two different points on the circle.)

Suggested fix: Alter "If the point (x0, y0) is equal to the point (x1, 
y1), or if the point (x1, y1) is equal to the point (x2, y2), then the 
method must add the point (x1, y1) to the subpath, and connect that 
point to the previous point (x0, y0) by a straight line." to include 
"... or if radius is 0".

"if the direction from (x0, y0) to (x1, y1) is the same as the direction 
from (x1, y1) to (x2, y2), then method must add the point (x1, y1) to 
the subpath" - s/then/then the/

Philip Taylor
Received on Sunday, 27 April 2008 15:57:43 UTC

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