source: Dev/trunk/src/client/dojox/dgauges/MultiLinearScaler.js

define(["dojo/_base/declare", "dojo/Stateful"], function(declare, Stateful){
        return declare("dojox.dgauges.MultiLinearScaler", Stateful, {
                // summary:
                //              The multi-linear scaler. This scaler maps numeric values according 
                //              to the majorTickValues content. 
                //              This allows display of very large value intervals that are difficult to render 
                //              with a linear scale. For example, if majorTickValues contains [0, 10, 50, 500, 2000], 
                //              the scale will show five major ticks with these values. 
                //              Note that this is not a logarithmic scale, the interpolation is linear between 
                //              two contiguous major ticks.
                //              Scalers are responsible for tick generation and various data-transform operations.      

                // majorTickValues: Array
                //              An array of Number for creating major ticks.
                //              This array must be sorted in ascendant order.
                majorTickValues: null,
                // minorTickCount: Array
                //              The number of minor ticks between two contiguous major ticks.
                //              The default value is 4.
                minorTickCount: 4,
                // majorTicks:
                //              The array of generated major ticks. You should not set this
                //              property when using the scaler.
                majorTicks: null,
                // minorTicks:
                //              The array of generated minor ticks. You should not set this
                //              property when using the scaler.
                minorTicks: null,
                _snapIntervalPrecision: null,
                _snapCount: 4,
                _snapIntervalPrecision: 6,
                
                constructor: function(){
                        this.watchedProperties = ["majorTickValues", "snapCount", "minorTickCount"];
                },
                                
                computeTicks: function(){
                        // summary:
                        //              Creates or re-creates the ticks for this scaler.
                        // returns: Array
                        //              An array containing all ticks (major then minor ticks).                 
                        this.majorTicks = [];
                        this.minorTicks = [];
                        var ti;
                        var step = 1 / (this.majorTickValues.length - 1);
                        var minorStep = step / (this.minorTickCount + 1);
                        var currentIndex = 0;
                        var minorInterval;
                        var currentMajorValue;
                        var v;
                        for(var i = 0; i < this.majorTickValues.length; i++){
                                v = this.majorTickValues[i];
                                ti = {scaler: this};
                                ti.position = currentIndex * step;
                                ti.value = v;
                                ti.isMinor = false;
                                this.majorTicks.push(ti);
                                if(currentIndex < this.majorTickValues.length - 1){
                                        currentMajorValue = Number(v);
                                        minorInterval = (Number(this.majorTickValues[i + 1]) - currentMajorValue) / (this.minorTickCount + 1);
                                        for(var j = 1; j <= this.minorTickCount; j++){
                                                ti = {scaler: this};
                                                ti.isMinor = true;
                                                ti.position = currentIndex * step + j * minorStep;
                                                ti.value = currentMajorValue + minorInterval * j;
                                                this.minorTicks.push(ti);
                                        }
                                }
                                currentIndex++;
                        }
                        return this.majorTicks.concat(this.minorTicks);
                },
                
                positionForValue: function(value){
                        // summary:
                        //              Transforms a value into a relative position between 0 and 1.
                        // value: Number
                        //              A value to transform.
                        // returns: Number
                        //              The position between 0 and 1.                   
                        if(!this.majorTickValues){
                                return 0;
                        }
                        
                        if(!this.majorTicks){
                                this.computeTicks();
                        }
                        
                        var minmax = this._getMinMax(value);
                        var position = (value - minmax[0].value) / (minmax[1].value - minmax[0].value);
                        return minmax[0].position + position * (minmax[1].position - minmax[0].position);
                },
                
                valueForPosition: function(position){
                        // summary:
                        //              Transforms a relative position (between 0 and 1) into a value.
                        // position: Number
                        //              A relative position to transform.
                        // returns: Number
                        //              The transformed value.
                        if(this.majorTicks == null){
                                return 0;
                        }
                        var minmax = this._getMinMax(position, "position");
                        var value = (position - minmax[0].position) / (minmax[1].position - minmax[0].position);
                        return minmax[0].value + value * (minmax[1].value - minmax[0].value);
                },
                
                _getMinMax: function(v, property){
                        // summary:
                        //              Internal method.
                        // tags:
                        //              private
                        if(!property){
                                property = "value";
                        }
                        var res = [];
                        var pre;
                        var post;
                        var left = 0;
                        var right = this.majorTicks.length - 1;
                        var center;
                        
                        if(v <= this.majorTicks[0][property] || v >= this.majorTicks[right][property]){
                                res[0] = this.majorTicks[0];
                                res[1] = this.majorTicks[right];
                                return res;
                        }
                        
                        while (true){
                                center = Math.floor((left + right) / 2);
                                
                                if(this.majorTicks[center][property] <= v){
                                        if(this.majorTicks[center + 1][property] >= v){
                                                res[0] = this.majorTicks[center];
                                                res[1] = this.majorTicks[center + 1];
                                                return res;
                                        }else{
                                                left = center + 1;
                                                continue;
                                        }
                                }else{
                                        right = center;
                                        continue;
                                }
                        }
                }
        });
});