- From: Jonas Sicking <jonas@sicking.cc>
- Date: Tue, 7 Sep 2010 22:36:31 -0700
This seems like a strange choice of behavior. Given that this is very likely a bug in the program, wouldn't it make more sense to throw an exception as to make it easier to debug? Similar to for example Node.appendChild when called with a null argument. / Jonas On Tue, Sep 7, 2010 at 10:32 PM, Sam Weinig <weinig at apple.com> wrote: > In 4.8.11.1 the spec does state: > > "Except where otherwise specified, for the 2D context interface, any method call with a numeric argument whose value is infinite or a NaN value must be ignored." > > -Sam > > On Sep 7, 2010, at 9:41 PM, Boris Zbarsky wrote: > >> Consider this testcase: >> >> <!doctype html> >> <html> >> ?<body> >> ? ?<canvas id="c" width="200" height="200"></canvas> >> ? ?<script> >> ? ?try { >> ? ? ?var c = document.getElementById("c"), >> ? ? ?t = c.getContext("2d"); >> ? ? ?t.moveTo(100, 100); >> ? ? ?t.lineTo(NaN, NaN); >> ? ? ?t.lineTo(50, 25); >> ? ? ?t.stroke(); >> ? ?} catch (e) {alert(e); } >> ? ?</script> >> ?</body> >> </html> >> >> Behavior in the spec seems to be undefined (in particular, no mention is made as to what the canvas API functions are supposed to do if non-finite values are passed in). ?Behavior in browsers is: >> >> Presto: Throws NOT_SUPPORTED_ERR on that lineTo(NaN, NaN) call. >> Gecko: Throws DOM_SYNTAX_ERR on that lineTo(NaN, NaN) call. >> Webkit: Silently ignores the lineTo(NaN, NaN) call, and then >> ? ? ? ?draws a line from (100,100) to (50, 25). >> >> Seems like the spec needs to define this. >> >> -Boris >> >> P.S. ?This isn't a hypothetical issue; this came up in a page that was trying to graph things using canvas and ending up with divide-by-0 all over the place. ?It "worked" in webkit (though not drawing the right thing, so much). ?It failed to draw anything in Presto or Gecko. > >
Received on Tuesday, 7 September 2010 22:36:31 UTC