Open Bug 363250 Opened 15 years ago Updated 9 months ago

implement toggle() expression


(Core :: CSS Parsing and Computation, enhancement)

Not set




(Reporter: dbaron, Unassigned)


(Blocks 4 open bugs, )


(Keywords: dev-doc-needed)

We should implement -moz-cycle() as described in:

The last of those messages is member-confidential, but since I wrote it, the entire contents are the following:

I'd like to resurrect an old proposal for addition to css3-values [1]:
This is particularly useful for styling HTML's UL and EM elements.

Proposed text that could be used in the specification is the following:


The cycle() expression allows descendant elements to cycle over a list
of values instead of inheriting the same value.  The syntax of the
cycle() expression is:

  cycle( <value> [, <value> ]*)

where <value> is a CSS value that is valid where the expression is
placed.  If any of the values inside are not valid, then the entire
cycle() expression is invalid.

The value returned by cycle() must be determined by comparing the
inherited value I (the computed value on the parent, or, for the root,
the initial value) to the computed values C[n] returned by the n-th
argument to cycle().  For the earliest C[n] such that C[n] == I, the
value returned by cycle is C[n+1].  However, if this C[n] is the last
value, or if there are no C[n] that equal I, the computed value of the
first value is returned instead.

Example 1:

  /* make em elements italic, but make them normal if they're inside
     something that's italic */
  em { font-style: cycle(italic, normal); }

Example 2:

  /* cycle between markers for nested lists, so that the top level has
     disk markers, but nested lists use circle, square, box, and then
     (for the 5th list deep) repeat */
  ul { list-style-type: disk; }
  li > ul { list-style-type: cycle(disk, circle, square, box); }


It could also be used in other interesting ways -- probably some bizarre
ones that I haven't even thought of yet.  Although I admit I have
already thought of:
  list-style-type: cycle(cycle(disc,disc,circle,circle), cycle(disc,circle),
                         cycle(square,square,box,box), cycle(square,box));
Understanding this is left as an exercise to the reader.

Blocks: 177496
The last example hurts my brain.
QA Contact: ian → style-system
Assignee: dbaron → nobody
This is very interesting, and while it probably has missed the CSS3 spec now, have you considered proposing it for CSS4?
The working group agreed to add it to css3-values; it just hasn't been added.
Perhaps they need a reminder :-) When was it discussed?
Blocks: css-values-3
Summary: implement -moz-cycle() expression → implement cycle() expression
This was renamed from cycle() to toggle().
Summary: implement cycle() expression → implement toggle() expression
Duplicate of this bug: 864009
Blocks: css3test
Duplicate of this bug: 1001365
Duplicate of this bug: 1380131
It's been 11 years and the status is still NEW. Wondering if toggle() expression is gonna be a priority anytime soon. Don't want to be a jerk, just curious as to what's keeping it in the dark for so long.
No longer depends on: 332335
Type: defect → enhancement
You need to log in before you can comment on or make changes to this bug.