Documentation for setOffsetAndWidth and fix for sieve documentations

Author: my-tien

src/traces/bar/cross_trace_calc.js

@@ -300,6 +300,18 @@ function setGroupPositionsInStackOrRelativeMode(gd, pa, sa, calcTraces, opts) {
     if(opts.norm) normalizeBars(sa, sieve, opts);
 }
 
+/**
+ * Mode group: Traces should be offsetted to other traces at the same position if they have a
+ *      different offsetgroup or if no offsetgroups are specified.
+ *      If there are no other traces at the same position, the trace will not be offsetted and it
+ *      can occupy the whole width.
+ *      If two traces share an offsetgroup, they should overlap.
+ * Mode overlay/stack/relative: Traces should be offseted to other traces at the same position if
+ *      they have a different offsetgroup.
+ *      If two traces share an offsetgroup or if no offsetgroups are specified, they should instead
+ *      overlap/stack.
+ * Angular axes (for barpolar type) don't support group offsets.
+ */
 function setOffsetAndWidth(gd, pa, sieve, opts) {
     var fullLayout = gd._fullLayout;
     var positions = sieve.positions;

src/traces/bar/sieve.js

@@ -66,6 +66,7 @@ function Sieve(traces, opts) {
  *
  * @method
  * @param {number} position
+ * @param {number} group
  * @param {number} value
  * @returns {number} Previous bin value
  */
@@ -83,6 +84,7 @@ Sieve.prototype.put = function put(position, group, value) {
  *
  * @method
  * @param {number} position  Position of datum
+ * @param {number} group
  * @param {number} [value]   Value of datum
  *                           (required if this.sepNegVal is true)
  * @returns {number} Current bin value
@@ -97,6 +99,7 @@ Sieve.prototype.get = function get(position, group, value) {
  *
  * @method
  * @param {number} position  Position of datum
+ * @param {number} group
  * @param {number} [value]   Value of datum
  *                           (required if this.sepNegVal is true)
  * @returns {string} Bin label