[OpenLayers-Users] Handler.RegularPolygon

[Tim Schaub]

Hey Tim-

I thought this was a great idea - and actually overlooked your 
attachment until just recently.  When I didn't see the example online, I 
started fresh on this.

Turns out it's quite different than the one that you put together.  I 
needed different sorts of configuration options.

So, for my version of regular polygon drawing (and approximating 
circles), see
http://dev.openlayers.org/sandbox/tschaub/feature/examples/regular-polygons.html

Thanks for the inspiration,
Tim

(Note that this requires a few patches that aren't in the trunk yet.)

Tim Langlois wrote:
> I wrote a custom handler to draw an N-sided regular polygon by clicking
> and dragging a line to specify the radius.  The polygon is drawn on
> mouse up.  The number of sides is specified by the "sides" attribute.
> 
> Here's an example.  Click the polygon button in the toolbar in the upper
> right corner and click and drag to create the polygon.  To change the
> sides, enter the number of sides you want and click submit.
> 
> http://maps.terratrace.net/mapserver/vmaptest.html
> 
> Attached is the handler code.
> 
> 
> 
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> 
> 
> ------------------------------------------------------------------------
> 
> /** * Handler to draw an N sided regular ploygon on the map. A point is 
> drawn on mouse down, * a line is drawn on mouse move (representing the 
> radius), and the polygon is drawn on mouse up. * Use the "sides" option 
> to set the number of polygon sides. * * @class * @requires 
> OpenLayers/Handler/Point.js * @requires OpenLayers/Geometry/Polygon.js 
> */ OpenLayers.Handler.RegularPolygon = OpenLayers.Class.create(); 
> OpenLayers.Handler.RegularPolygon.prototype = 
> OpenLayers.Class.inherit(OpenLayers.Handler.Point, { /** * @type 
> OpenLayers.Feature.Vector * @private */ line: null, /** * @type 
> OpenLayers.Feature.Vector * @private */ regularPolygon: null, /** * The 
> number of sides the polygon will have * @type int */ sides: 50, /** * 
> @constructor * * @param {OpenLayers.Control} control * @param {Array} 
> callbacks An object with a 'done' property whos value is * a function to 
> be called when the path drawing is * finished. The callback should 
> expect to recieve a * single argument, the polygon geometry. * If the 
> callbacks object contains a 'point' * property, this function will be 
> sent each point * as they are added. If the callbacks object contains * 
> a 'cancel' property, this function will be called when * the handler is 
> deactivated while drawing. The cancel * should expect to receive a 
> geometry. * @param {Object} options */ initialize: function(control, 
> callbacks, options) { 
> OpenLayers.Handler.Point.prototype.initialize.apply(this, arguments); }, 
> /** * Add temporary geometries */ createFeature: function() { this.line 
> = new OpenLayers.Feature.Vector(new OpenLayers.Geometry.LineString()); 
> this.point = new OpenLayers.Feature.Vector(new 
> OpenLayers.Geometry.Point()); this.regularPolygon = new 
> OpenLayers.Feature.Vector(new OpenLayers.Geometry.Polygon()); }, /** * 
> Destroy temporary geometries */ destroyFeature: function() { 
> this.line.destroy(); this.point.destroy(); 
> this.regularPolygon.destroy(); this.line = null; this.regularPolygon = 
> null; }, /** * Modify the existing geometry given the new point * */ 
> modifyFeature: function() { var index = 
> this.line.geometry.components.length - 1; 
> this.line.geometry.components[index].x = this.point.geometry.x; 
> this.line.geometry.components[index].y = this.point.geometry.y; }, /** * 
> Render geometries on the temporary layer. */ drawFeature: function() { 
> this.layer.drawFeature(this.line, this.style); 
> this.layer.drawFeature(this.point, this.style); }, /** * Add point to 
> geometry. Send the point index to override * the behavior of LinearRing 
> that disregards adding duplicate points. */ addPoint: function() { 
> this.line.geometry.addComponent(this.point.geometry.clone(), 
> this.line.geometry.components.length); this.callback("point", 
> [this.point.geometry]); }, /** * Return a clone of the relevant 
> geometry. * * @type OpenLayers.Geometry.LineString */ geometryClone: 
> function() { return this.regularPolygon.geometry.clone(); }, 
> createRegularPolygon: function() { var pointList = []; // the radius is 
> the length of the line segment var radius = 
> this.line.geometry.getLength(); // draw the polygon, the center is the 
> first point drawn at mousedown if (radius > 0) { var cenx = 
> this.line.geometry.components[0].x; var ceny = 
> this.line.geometry.components[0].y; var piNum = Math.PI * 2; var 
> segments = piNum / this.sides; for (var a = 0; a < piNum; a += segments) 
> { var x = cenx + radius * Math.sin(a); var y = ceny + radius * 
> Math.cos(a); var newPoint = new OpenLayers.Geometry.Point(x,y); 
> pointList.push(newPoint); } pointList.push(pointList[0]); var linearRing 
> = new OpenLayers.Geometry.LinearRing(pointList); 
> this.regularPolygon.geometry.addComponent(linearRing); } }, /** * Return 
> the radius of the polygon * * @type int */ getRadius: function() { 
> this.line.geometry.getLength(); }, /** * Handle mouse down. Add the 
> starting (center) point of the polygon and render it * Return determines 
> whether to propagate the event on the map. * * @param {Event} evt * 
> @type Boolean */ mousedown: function(evt) { if(this.line == null) { 
> this.createFeature(); } this.mouseDown = true; var lonlat = 
> this.control.map.getLonLatFromPixel(evt.xy); this.point.geometry.x = 
> lonlat.lon; this.point.geometry.y = lonlat.lat; this.addPoint(); 
> this.drawFeature(); return false; }, /** * Handle mouse move. Adjust the 
> geometry and redraw the line. * Return determines whether to propagate 
> the event on the map. * * @param {Event} evt * @type Boolean */ 
> mousemove: function (evt) { if ((this.line == null) || 
> (this.line.geometry == null)) return true; 
> if(this.line.geometry.components.length > 0) { var lonlat = 
> this.map.getLonLatFromPixel(evt.xy); if 
> (this.line.geometry.components.length == 1) { this.point = new 
> OpenLayers.Feature.Vector(new OpenLayers.Geometry.Point()); 
> this.addPoint(); } this.point.geometry.x = lonlat.lon; 
> this.point.geometry.y = lonlat.lat; this.modifyFeature(); 
> this.drawFeature(); } return false; }, /** * Handle mouse up. Send the 
> last point in the geometry to the control. If we * have a valid line 
> segment (radius), then draw the polygon. * Return determines whether to 
> propagate the event on the map. * * @param {Event} evt * @type Boolean 
> */ mouseup: function (evt) { this.mouseDown = false; if 
> (this.line.geometry.components.length == 2) { 
> this.createRegularPolygon(); } this.point.destroy(); 
> this.line.destroy(); this.finalize(); return false; }, /** @final @type 
> String */ CLASS_NAME: "OpenLayers.Handler.RegularPolygon" });
> 
> 
> ------------------------------------------------------------------------
> 
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