对jqplot的CategoryAxisRenderer插件进行扩展，底部Tick在鼠标在上时浮动显示名称。

在前一篇文章中介绍了如何让jqplot的柱形图tick下标出现省略号，参考：
《对jqplot的CategoryAxisRenderer插件进行扩展，让文字出现省略号》
http://xianbin.iteye.com/blog/1701667

下面介绍如何扩展jqplot，让其实现鼠标移动到下标tick的时候出现浮动提示框，显示完整的tick名称。

文件命名为：jqplot.categoryAxisRenderer.extend.js
在引入jqplot.categoryAxisRenderer.js之后，再引入该js，以便覆盖原有的实现。下面代码已经实现了将tick下标显示为带省略号的文字并出现浮动提示框。

/**
 * 本扩展插件是对jqplot插件jqplot.categoryAxisRenderer的扩展，主要修改了显示图形下标Tick的处理，
 * 在显示Tick之前，判断Tick标签的长度，当标题长度超过tickMaxLength定义的长度时，截获前
 * tickMaxLength - 1个字符，然后加上省略号。
 * 
 * 作者：suxianbin
 */
(function($) {
    $.jqplot.CategoryAxisRenderer.prototype.createTicks = function() {
        // we're are operating on an axis here
        var ticks = this._ticks;
        var userTicks = this.ticks;
        var name = this.name;
        // databounds were set on axis initialization.
        var db = this._dataBounds;
        var dim, interval;
        var min, max;
        var pos1, pos2;
        var tt, i;
        
        // X轴的标题文字最大长度
        var tickMaxLength = this.tickMaxLength;

        // if we already have ticks, use them.
        if (userTicks.length) {
            // adjust with blanks if we have groups
            if (this.groups > 1 && !this._grouped) {
                var l = userTicks.length;
                var skip = parseInt(l/this.groups, 10);
                var count = 0;
                for (var i=skip; i<l; i+=skip) {
                    userTicks.splice(i+count, 0, ' ');
                    count++;
                }
                this._grouped = true;
            }
            this.min = 0.5;
            this.max = userTicks.length + 0.5;
            var range = this.max - this.min;
            this.numberTicks = 2*userTicks.length + 1;
            for (i=0; i<userTicks.length; i++){
                tt = this.min + 2 * i * range / (this.numberTicks-1);
                // need a marker before and after the tick
                var t = new this.tickRenderer(this.tickOptions);
                t.showLabel = false;
                // t.showMark = true;
                t.setTick(tt, this.name);
                this._ticks.push(t);
                var t = new this.tickRenderer(this.tickOptions);
                
                // 当标题长度超过tickMaxLength定义的长度时，截获前tickMaxLength - 1个字符，
                // 然后加上省略号。
				if (tickMaxLength) {
					var userTick = userTicks[i].length <= tickMaxLength ? userTicks[i]
							: userTicks[i].substring(0, (tickMaxLength - 1)) + '...';
					t.label = userTick;
					t.userTick = userTicks[i];
				} else {
					t.label = userTicks[i];
				}
                
                // t.showLabel = true;
                t.showMark = false;
                t.showGridline = false;
                t.setTick(tt+0.5, this.name);
                this._ticks.push(t);
            }
            // now add the last tick at the end
            var t = new this.tickRenderer(this.tickOptions);
            t.showLabel = false;
            // t.showMark = true;
            t.setTick(tt+1, this.name);
            this._ticks.push(t);
        }

        // we don't have any ticks yet, let's make some!
        else {
            if (name == 'xaxis' || name == 'x2axis') {
                dim = this._plotDimensions.width;
            }
            else {
                dim = this._plotDimensions.height;
            }
            
            // if min, max and number of ticks specified, user can't specify interval.
            if (this.min != null && this.max != null && this.numberTicks != null) {
                this.tickInterval = null;
            }
            
            // if max, min, and interval specified and interval won't fit, ignore interval.
            if (this.min != null && this.max != null && this.tickInterval != null) {
                if (parseInt((this.max-this.min)/this.tickInterval, 10) != (this.max-this.min)/this.tickInterval) {
                    this.tickInterval = null;
                }
            }
        
            // find out how many categories are in the lines and collect labels
            var labels = [];
            var numcats = 0;
            var min = 0.5;
            var max, val;
            var isMerged = false;
            for (var i=0; i<this._series.length; i++) {
                var s = this._series[i];
                for (var j=0; j<s.data.length; j++) {
                    if (this.name == 'xaxis' || this.name == 'x2axis') {
                        val = s.data[j][0];
                    }
                    else {
                        val = s.data[j][1];
                    }
                    if ($.inArray(val, labels) == -1) {
                        isMerged = true;
                        numcats += 1;      
                        labels.push(val);
                    }
                }
            }
            
            if (isMerged && this.sortMergedLabels) {
                labels.sort(function(a,b) { return a - b; });
            }
            
            // keep a reference to these tick labels to use for redrawing plot (see bug #57)
            this.ticks = labels;
            
            // now bin the data values to the right lables.
            for (var i=0; i<this._series.length; i++) {
                var s = this._series[i];
                for (var j=0; j<s.data.length; j++) {
                    if (this.name == 'xaxis' || this.name == 'x2axis') {
                        val = s.data[j][0];
                    }
                    else {
                        val = s.data[j][1];
                    }
                    // for category axis, force the values into category bins.
                    // we should have the value in the label array now.
                    var idx = $.inArray(val, labels)+1;
                    if (this.name == 'xaxis' || this.name == 'x2axis') {
                        s.data[j][0] = idx;
                    }
                    else {
                        s.data[j][1] = idx;
                    }
                }
            }
            
            // adjust with blanks if we have groups
            if (this.groups > 1 && !this._grouped) {
                var l = labels.length;
                var skip = parseInt(l/this.groups, 10);
                var count = 0;
                for (var i=skip; i<l; i+=skip+1) {
                    labels[i] = ' ';
                }
                this._grouped = true;
            }
        
            max = numcats + 0.5;
            if (this.numberTicks == null) {
                this.numberTicks = 2*numcats + 1;
            }

            var range = max - min;
            this.min = min;
            this.max = max;
            var track = 0;
            
            // todo: adjust this so more ticks displayed.
            var maxVisibleTicks = parseInt(3+dim/10, 10);
            var skip = parseInt(numcats/maxVisibleTicks, 10);

            if (this.tickInterval == null) {

                this.tickInterval = range / (this.numberTicks-1);

            }
            // if tickInterval is specified, we will ignore any computed maximum.
            for (var i=0; i<this.numberTicks; i++){
                tt = this.min + i * this.tickInterval;
                var t = new this.tickRenderer(this.tickOptions);
                // if even tick, it isn't a category, it's a divider
                if (i/2 == parseInt(i/2, 10)) {
                    t.showLabel = false;
                    t.showMark = true;
                }
                else {
                    if (skip>0 && track<skip) {
                        t.showLabel = false;
                        track += 1;
                    }
                    else {
                        t.showLabel = true;
                        track = 0;
                    } 
                    t.label = t.formatter(t.formatString, labels[(i-1)/2]);
                    t.showMark = false;
                    t.showGridline = false;
                }
                t.setTick(tt, this.name);
                this._ticks.push(t);
            }
        }
    };
    
    
    // called with scope of axis
    $.jqplot.CategoryAxisRenderer.prototype.pack = function(pos, offsets) {
        var ticks = this._ticks;
        var max = this.max;
        var min = this.min;
        var offmax = offsets.max;
        var offmin = offsets.min;
        var lshow = (this._label == null) ? false : this._label.show;
        var i;
		
        for (var p in pos) {
            this._elem.css(p, pos[p]);
        }
        
        this._offsets = offsets;
        // pixellength will be + for x axes and - for y axes becasue pixels always measured from top left.
        var pixellength = offmax - offmin;
        var unitlength = max - min;
        
        // point to unit and unit to point conversions references to Plot DOM element top left corner.
        this.p2u = function(p){
            return (p - offmin) * unitlength / pixellength + min;
        };
        
        this.u2p = function(u){
            return (u - min) * pixellength / unitlength + offmin;
        };
                
        if (this.name == 'xaxis' || this.name == 'x2axis'){
            this.series_u2p = function(u){
                return (u - min) * pixellength / unitlength;
            };
            this.series_p2u = function(p){
                return p * unitlength / pixellength + min;
            };
        }
        
        else {
            this.series_u2p = function(u){
                return (u - max) * pixellength / unitlength;
            };
            this.series_p2u = function(p){
                return p * unitlength / pixellength + max;
            };
        }
        
        if (this.show) {
            if (this.name == 'xaxis' || this.name == 'x2axis') {
                for (i=0; i<ticks.length; i++) {
                    var t = ticks[i];
                    if (t.show && t.showLabel) {
                        var shim;
                        
                        if (t.constructor == $.jqplot.CanvasAxisTickRenderer && t.angle) {
                            // will need to adjust auto positioning based on which axis this is.
                            var temp = (this.name == 'xaxis') ? 1 : -1;
                            switch (t.labelPosition) {
                                case 'auto':
                                    // position at end
                                    if (temp * t.angle < 0) {
                                        shim = -t.getWidth() + t._textRenderer.height * Math.sin(-t._textRenderer.angle) / 2;
                                    }
                                    // position at start
                                    else {
                                        shim = -t._textRenderer.height * Math.sin(t._textRenderer.angle) / 2;
                                    }
                                    break;
                                case 'end':
                                    shim = -t.getWidth() + t._textRenderer.height * Math.sin(-t._textRenderer.angle) / 2;
                                    break;
                                case 'start':
                                    shim = -t._textRenderer.height * Math.sin(t._textRenderer.angle) / 2;
                                    break;
                                case 'middle':
                                    shim = -t.getWidth()/2 + t._textRenderer.height * Math.sin(-t._textRenderer.angle) / 2;
                                    break;
                                default:
                                    shim = -t.getWidth()/2 + t._textRenderer.height * Math.sin(-t._textRenderer.angle) / 2;
                                    break;
                            }
                        }
                        else {
                            shim = -t.getWidth()/2;
                        }
                        var val = this.u2p(t.value) + shim + 'px';
                        t._elem.css('left', val);
                        t.pack();

                        /*
                         * 增加X轴Tick的弹出提醒框，内容为下标的全称。
                         */
                        t._elem.css('cursor', 'default');
                        t._elem.css('z-index', 888);
                        t._elem.attr('userTick', t.userTick);
                        
                        t._elem.mouseover(function (e) {
                        	var userTick = $(this).attr('usertick');
                        	_showUserTickTip(userTick, e);
                        });
                        
                        t._elem.mouseout(function () {
                        	_hideUserTickTip();
                        });
                    }
                }
                
                var labeledge=['bottom', 0];
                if (lshow) {
                    var w = this._label._elem.outerWidth(true);
                    this._label._elem.css('left', offmin + pixellength/2 - w/2 + 'px');
                    if (this.name == 'xaxis') {
                        this._label._elem.css('bottom', '0px');
                        labeledge = ['bottom', this._label._elem.outerHeight(true)];
                    }
                    else {
                        this._label._elem.css('top', '0px');
                        labeledge = ['top', this._label._elem.outerHeight(true)];
                    }
                    this._label.pack();
                }
                
                // draw the group labels
                var step = parseInt(this._ticks.length/this.groups, 10);
                for (i=0; i<this._groupLabels.length; i++) {
                    var mid = 0;
                    var count = 0;
                    for (var j=i*step; j<=(i+1)*step; j++) {
                        if (this._ticks[j]._elem && this._ticks[j].label != " ") {
                            var t = this._ticks[j]._elem;
                            var p = t.position();
                            mid += p.left + t.outerWidth(true)/2;
                            count++;
                        }
                    }
                    mid = mid/count;
                    this._groupLabels[i].css({'left':(mid - this._groupLabels[i].outerWidth(true)/2)});
                    this._groupLabels[i].css(labeledge[0], labeledge[1]);
                }
            }
            else {
                for (i=0; i<ticks.length; i++) {
                    var t = ticks[i];
                    if (t.show && t.showLabel) {                        
                        var shim;
                        if (t.constructor == $.jqplot.CanvasAxisTickRenderer && t.angle) {
                            // will need to adjust auto positioning based on which axis this is.
                            var temp = (this.name == 'yaxis') ? 1 : -1;
                            switch (t.labelPosition) {
                                case 'auto':
                                    // position at end
                                case 'end':
                                    if (temp * t.angle < 0) {
                                        shim = -t._textRenderer.height * Math.cos(-t._textRenderer.angle) / 2;
                                    }
                                    else {
                                        shim = -t.getHeight() + t._textRenderer.height * Math.cos(t._textRenderer.angle) / 2;
                                    }
                                    break;
                                case 'start':
                                    if (t.angle > 0) {
                                        shim = -t._textRenderer.height * Math.cos(-t._textRenderer.angle) / 2;
                                    }
                                    else {
                                        shim = -t.getHeight() + t._textRenderer.height * Math.cos(t._textRenderer.angle) / 2;
                                    }
                                    break;
                                case 'middle':
                                    // if (t.angle > 0) {
                                    //     shim = -t.getHeight()/2 + t._textRenderer.height * Math.sin(-t._textRenderer.angle) / 2;
                                    // }
                                    // else {
                                    //     shim = -t.getHeight()/2 - t._textRenderer.height * Math.sin(t._textRenderer.angle) / 2;
                                    // }
                                    shim = -t.getHeight()/2;
                                    break;
                                default:
                                    shim = -t.getHeight()/2;
                                    break;
                            }
                        }
                        else {
                            shim = -t.getHeight()/2;
                        }
                        
                        var val = this.u2p(t.value) + shim + 'px';
                        t._elem.css('top', val);
                        t.pack();
                    }
                }
                
                var labeledge=['left', 0];
                if (lshow) {
                    var h = this._label._elem.outerHeight(true);
                    this._label._elem.css('top', offmax - pixellength/2 - h/2 + 'px');
                    if (this.name == 'yaxis') {
                        this._label._elem.css('left', '0px');
                        labeledge = ['left', this._label._elem.outerWidth(true)];
                    }
                    else {
                        this._label._elem.css('right', '0px');
                        labeledge = ['right', this._label._elem.outerWidth(true)];
                    }   
                    this._label.pack();
                }
                
                // draw the group labels, position top here, do left after label position.
                var step = parseInt(this._ticks.length/this.groups, 10);
                for (i=0; i<this._groupLabels.length; i++) {
                    var mid = 0;
                    var count = 0;
                    for (var j=i*step; j<=(i+1)*step; j++) {
                        if (this._ticks[j]._elem && this._ticks[j].label != " ") {
                            var t = this._ticks[j]._elem;
                            var p = t.position();
                            mid += p.top + t.outerHeight()/2;
                            count++;
                        }
                    }
                    mid = mid/count;
                    this._groupLabels[i].css({'top':mid - this._groupLabels[i].outerHeight()/2});
                    this._groupLabels[i].css(labeledge[0], labeledge[1]);
                    
                }
            }
        }
    };

    // 显示Tick下标全称的提示框
    function _showUserTickTip(userTick, event) {
		var containerId = 'userTickTipDiv';
		var container = $('#' + containerId);
		if (container == undefined || container == null || container.length == 0) {
			container = $('<div class="jqplot-cursor-tooltip chartDetailDiv"></div>');
			container.attr('id', containerId);

			var table = '<table class="jqplot-highlighter">'
					+ '<tr><td><span id="userTickValue"></span></td></tr>'
					+ '</table>';
			$(table).appendTo(container);
			container.appendTo('body');
		}
		
		$('#userTickValue').text(userTick);
		
		// 计算显示框的位置，如果超过右边边界则在左边显示
		var left = event.pageX;
		var detailPopDivWidth = container.width();
		var docWidth = $(window).width();
		var leftX = left + detailPopDivWidth + 10; // 10 表示与边界的间隔
		if (leftX > docWidth) {
			left = event.pageX - detailPopDivWidth;
		}

		container.css({
			display : 'block',
			left : left,
			top : event.pageY - 25
		});
	}
    
    // 隐藏Tick下标全称的提示框
    function _hideUserTickTip() {
		$('#userTickTipDiv').css({
			display : 'none'
		});
    }

})(jQuery);