source: Dev/trunk/src/client/dojox/drawing/util/positioning.js

define(['./common'], function(common){
        
        var textOffset = 4;  // distance from line to text box
        var textYOffset = 20;  // height of text box
        
        var positioning = {};
        positioning.label = function(/*Object*/start, /*Object*/end){
                // summary:
                //              Returns the optimal text positions for annotations.Label.
                
                // label at middle of vector
                var x = 0.5*(start.x+end.x);
                var y = 0.5*(start.y+end.y);
                
                // move label a set distance from the line
                var slope = common.slope(start, end);
                var deltay = textOffset/Math.sqrt(1.0+slope*slope);
                
                if(end.y>start.y && end.x>start.x || end.y<start.y && end.x<start.x){
                        // Position depending on quadrant.  Y offset
                        // positions box aligned vertically from top
                        deltay = -deltay;
                        y -= textYOffset;
                }
                x += -deltay*slope;
                y += deltay;
                
                // want text to be away from start of vector
                // This will make force diagrams less crowded
                var align = end.x<start.x ? "end" : "start";
                
                return { x:x, y:y, foo:"bar", align:align}; // Object
        };
        
        positioning.angle = function(/*Object*/start, /*Object*/end){
                // summary:
                //              Returns the optimal position for annotations.Angle.

                // angle at first third of vector
                var x = 0.7*start.x+0.3*end.x;
                var y = 0.7*start.y+0.3*end.y;

                // move label a set distance from the line
                var slope = common.slope(start, end);
                var deltay = textOffset/Math.sqrt(1.0+slope*slope);
                
                if(end.x<start.x){deltay = -deltay;}
                x += -deltay * slope;
                y += deltay;
                
                // want text to be clockwise from vector
                // to match angle measurement from x-axis
                var align = end.y>start.y ? "end" : "start";
                // box vertical aligned from middle
                y += end.x > start.x ? 0.5*textYOffset :  -0.5*textYOffset;
                
                return { x:x, y:y, align:align}; // Object
        };
        
        return positioning;
});