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

define(["dojo/_base/lang", "dojo/_base/declare", "dojo/Stateful"], function(lang, declare, Stateful){
        return declare("dojox.dgauges.LinearScaler", Stateful, {
                // summary:
                //              The linear scaler. This scaler creates major and minor ticks regularly between 
                //              a minimum and a maximum.
                //              Scalers are responsible for tick generation and various data-transform operations.              
                
                // minimum: Number
                //              The minimum value of the scaler. Default is 0.
                minimum: 0,
                // maximum: Number
                //              The maximum value of the scaler. Default is 100.
                maximum: 100,
                // snapInterval:
                //              Specifies the increment value to be used as snap values on this scale 
                //              during user interaction.
                //              Default is 1.
                snapInterval: 1,
                // majorTickInterval: Number
                //              The interval between two major ticks.
                majorTickInterval: NaN,
                // minorTickInterval: Number
                //              The interval between two minor ticks.
                minorTickInterval: NaN,
                // minorTicksEnabled: Boolean
                //              If false, minor ticks are not generated. Default is true.
                minorTicksEnabled: true,
                // 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,

                _computedMajorTickInterval: NaN,
                _computedMinorTickInterval: NaN,
                
                constructor: function(){
                        this.watchedProperties = ["minimum", "maximum", "majorTickInterval", "minorTickInterval", "snapInterval", "minorTicksEnabled"];
                },

                _buildMinorTickItems: function(){
                        // summary:
                        //              Internal method.
                        // tags:
                        //              private
                        var mt = this.majorTicks;
                        var minorTickCache = [];
                        if(this.maximum > this.minimum){
                                var majorTickCount = Math.floor((this.maximum - this.minimum) / this.getComputedMajorTickInterval()) + 1;
                                var minorTickCount = Math.floor(this.getComputedMajorTickInterval() / this.getComputedMinorTickInterval());
                                var data;
                                for(var i = 0; i < majorTickCount - 1; i++){
                                        for(var j = 1; j < minorTickCount; j++){
                                                data = {scaler: this};
                                                data.isMinor = true;
                                                data.value = mt[i].value + j * this.getComputedMinorTickInterval();
                                                data.position = (Number(data.value) - this.minimum) / (this.maximum - this.minimum);
                                                minorTickCache.push(data);
                                        }
                                }
                        }
                        return minorTickCache;
                },
                
                _buildMajorTickItems: function(){
                        // summary:
                        //              Internal method.
                        // tags:
                        //              private
                        var majorTickCache = [];
                        if(this.maximum > this.minimum){
                                var majorTickCount = Math.floor((this.maximum - this.minimum) / this.getComputedMajorTickInterval()) + 1;
                                var data;
                                for(var i = 0; i < majorTickCount; i++){
                                        data = {scaler: this};
                                        data.isMinor = false;
                                        data.value = this.minimum + i * this.getComputedMajorTickInterval();
                                        data.position = (Number(data.value) - this.minimum) / (this.maximum - this.minimum);
                                        majorTickCache.push(data);
                                }
                        }
                        return majorTickCache;
                },
                
                getComputedMajorTickInterval: function(){
                        // summary:
                        //              The computed or user defined major tick interval.
                        // returns: Number
                        //              The major tick interval used for ticks generation.
                        if(!isNaN(this.majorTickInterval)){
                                return this.majorTickInterval;
                        }
                        if(isNaN(this._computedMajorTickInterval)){
                                this._computedMajorTickInterval = (this.maximum - this.minimum) / 10;
                        }
                        return this._computedMajorTickInterval;
                },
                
                getComputedMinorTickInterval: function(){
                        // summary:
                        //              The computed or user defined minor tick interval.
                        // returns: Number
                        //              The minor tick interval used for ticks generation.
                        if(!isNaN(this.minorTickInterval)){
                                return this.minorTickInterval;
                        }
                        if(isNaN(this._computedMinorTickInterval)){
                                this._computedMinorTickInterval = this.getComputedMajorTickInterval() / 5;
                        }
                        return this._computedMinorTickInterval;
                },
                
                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._buildMajorTickItems();
                        this.minorTicks = this.minorTicksEnabled ? this._buildMinorTickItems() : [];
                        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.
                        var position;
                        if(value == null || isNaN(value) || value <= this.minimum){
                                position = 0;
                        }
                        if(value >= this.maximum){
                                position = 1;
                        }
                        if(isNaN(position)){
                                position = (value - this.minimum) / (this.maximum - this.minimum);
                        }
                        return 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 between minimum and maximum.
                        var range = Math.abs(this.minimum - this.maximum);
                        var value = this.minimum + range * position;
                        if(!isNaN(this.snapInterval) && this.snapInterval > 0){
                                value = Math.round((value - this.minimum) / this.snapInterval) * this.snapInterval + this.minimum;
                        }
                        return value;
                }
        });
});