[whatwg] Implementation issue: step mismatch handling for <input type=range>
Jonathan Watt
jwatt at jwatt.org
Thu Jan 17 11:29:44 PST 2013
I'm working on implementing <input type=range> for Gecko and have encountered
what I believe to be an issue in the spec.
Step 1 of the algorithm to find the "step base":
http://www.whatwg.org/specs/web-apps/current-work/multipage/common-input-element-attributes.html#concept-input-min-zero
says "If the element has a min content attribute...to the value of the min
content attribute...". Should this not talk about "minimum" rather than "min
content attribute"? It would otherwise seem to give bad results in the case of
<input type=range>, which has a default minimum of zero (a default minimum makes
sense in the case of type=range, since an unbounded slider would be impossible
for a user to interact with). Consider for example:
<input type=range value=-1 max=1 step=3>
As it stands, the current spec text says that the "step base" is -1 (from the
'value' content attribute), the 'minimum' is zero (from the default minimum),
the 'maximum' is 1, and the step is 3. As a result, an implementation would seem
to be directed to enter an infinite loop applying the paragraphs beginning with
"When the element is suffering from an underflow..." and "When the element is
suffering from a step mismatch..." in:
http://www.whatwg.org/specs/web-apps/current-work/multipage/states-of-the-type-attribute.html#range-state-%28type=range%29
If the step base considered the 'minimum' instead of the 'min' content
attribute, then the step base would be zero, and thus the value would settle at
zero.
Jonathan
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