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Starling's 'QuadSection' extension modified so that it shows just a half-circle.
package starling.extensions
{
import flash.geom.Point;
import starling.display.Mesh;
import starling.rendering.IndexData;
import starling.rendering.VertexData;
import starling.textures.Texture;
public class QuadSectionArc extends Mesh
{
private var _width:Number;
private var _height:Number;
private var _color:uint;
private var _slices:Array;
private var _ratio:Number;
private var _clockwise:Boolean;
private static var sPoint:Point = new Point();
public function QuadSectionArc(width:Number, height:Number, color:uint=0xffffff)
{
_color = color;
_width = width;
_height = height;
_ratio = 1.0;
_clockwise = true;
_slices = [
{ ratio: 0.0, x: 0, y: _height },
{ ratio: 0.25, x: 0, y: 0 },
{ ratio: 0.75, x: _width, y: 0 },
{ ratio: 1.0, x: _width, y: _height }
];
var vertexData:VertexData = new VertexData(null, 5);
var indexData:IndexData = new IndexData(9);
super(vertexData, indexData);
this.updateVertices();
}
private function updateVertices():void
{
vertexData.numVertices = 0;
indexData.numIndices = 0;
if (_ratio > 0)
{
var angle:Number = _ratio * Math.PI;
var numSlices:int = _slices.length;
updateVertex(0, _width / 2, _height); // origin
for (var i:int=1; i<numSlices; ++i)
{
var currSlice:Object = _slices[i];
var prevSlice:Object = _slices[i - 1];
var nextVertexID:int = i < 6 ? i + 1 : 1;
indexData.addTriangle(0, i, nextVertexID);
updateVertex(i, prevSlice.x, prevSlice.y);
if (_ratio > currSlice.ratio)
updateVertex(nextVertexID, currSlice.x, currSlice.y);
else
{
intersectLineWithSlice(
prevSlice.x, prevSlice.y, currSlice.x, currSlice.y, angle, sPoint);
updateVertex(nextVertexID, sPoint.x, sPoint.y);
break;
}
}
}
setVertexDataChanged();
}
private function updateVertex(vertexID:int, x:Number, y:Number):void
{
if (!_clockwise)
x = _width - x;
if (texture)
texture.setTexCoords(vertexData, vertexID, "texCoords", x / _width, y / _height);
vertexData.setPoint(vertexID, "position", x, y);
vertexData.setColor(vertexID, "color", _color);
}
private function intersectLineWithSlice(ax:Number, ay:Number, bx:Number, by:Number,
angle:Number, out:Point=null):Point
{
out ||= new Point();
if (ax == bx && ay == by) return null; // length = 0
var abx:Number = bx - ax;
var aby:Number = by - ay;
var cdx:Number = Math.cos(angle);
var cdy:Number = Math.sin(angle);
var tDen:Number = cdy * abx - cdx * aby;
if (tDen == 0.0) return null; // parallel or identical
var cx:Number = _width / 2.0;
var cy:Number = _height;
var t:Number = (aby * (cx - ax) - abx * (cy - ay)) / tDen;
out.x = cx + t * cdx;
out.y = cy + t * cdy;
return out;
}
override public function get color():uint { return _color; }
override public function set color(value:uint):void { super.color = _color = value; }
override public function set texture(value:Texture):void
{
super.texture = value;
if (value.frame) trace("Warning: 'QuadSection' will ignore any texture frames.");
updateVertices();
}
public function get ratio():Number { return _ratio; }
public function set ratio(value:Number):void
{
if (_ratio != value)
{
_ratio = value;
updateVertices();
}
}
public function get clockwise():Boolean { return _clockwise; }
public function set clockwise(value:Boolean):void
{
if (_clockwise != value)
{
_clockwise = value;
updateVertices();
}
}
public static function fromTexture(texture:Texture):QuadSection
{
var quadPie:QuadSection = new QuadSection(texture.width, texture.height);
quadPie.texture = texture;
return quadPie;
}
}
}
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