FX.options.duration can be a function

[guiguibonbon]

Sorry, don't know how to submit a patch.

        start: function(from, to){
 	                if (!this.options.wait) this.stop();
 	                else if (this.timer) return this;
 	                this.from = from;
 	                this.to = to;
 	                this.change = this.to - this.from;
 	                if (typeof this.options.duration == "function")
 	                    this.options.duration = this.options.duration(this.change, this.from, this.to);
 	                this.timer = this.step.periodical(Math.round(1000 / this.options.fps), this);
 	                this.fireEvent('onStart', this.element);
 	                return this;
 	        },

forum thread

[ibolmo]

Will be considered for 1.3's Effects enhancement.