embox2d-helpers.js

//Having to type 'Box2D.' in front of everything makes porting//existing C++ code a pain in the butt. This function can be used//to make everything in the Box2D namespace available without//needing to do that.function using(ns, pattern) {        if (pattern == undefined) {        // import all        for (var name in ns) {            this[name] = ns[name];        }    } else {        if (typeof(pattern) == 'string') {            pattern = new RegExp(pattern);        }        // import only stuff matching given pattern        for (var name in ns) {            if (name.match(pattern)) {                this[name] = ns[name];            }        }           }}//to replace original C++ operator =function copyVec2(vec) {    return new Box2D.b2Vec2(vec.get_x(), vec.get_y());}//to replace original C++ operator * (float)function scaleVec2(vec, scale) {    vec.set_x( scale * vec.get_x() );    vec.set_y( scale * vec.get_y() );            }//to replace original C++ operator *= (float)function scaledVec2(vec, scale) {    return new Box2D.b2Vec2(scale * vec.get_x(), scale * vec.get_y());}// http://stackoverflow.com/questions/12792486/emscripten-bindings-how-to-create-an-accessible-c-c-array-from-javascriptfunction createChainShape(vertices, closedLoop) {    var shape = new Box2D.b2ChainShape();                var buffer = Box2D.allocate(vertices.length * 8, 'float', Box2D.ALLOC_STACK);    var offset = 0;    for (var i=0;i<vertices.length;i++) {        Box2D.setValue(buffer+(offset), vertices[i].get_x(), 'float'); // x        Box2D.setValue(buffer+(offset+4), vertices[i].get_y(), 'float'); // y        offset += 8;    }                var ptr_wrapped = Box2D.wrapPointer(buffer, Box2D.b2Vec2);    if ( closedLoop )        shape.CreateLoop(ptr_wrapped, vertices.length);    else        shape.CreateChain(ptr_wrapped, vertices.length);    return shape;}function createPolygonShape(vertices) {    var shape = new Box2D.b2PolygonShape();                var buffer = Box2D.allocate(vertices.length * 8, 'float', Box2D.ALLOC_STACK);    var offset = 0;    for (var i=0;i<vertices.length;i++) {        Box2D.setValue(buffer+(offset), vertices[i].get_x(), 'float'); // x        Box2D.setValue(buffer+(offset+4), vertices[i].get_y(), 'float'); // y        offset += 8;    }                var ptr_wrapped = Box2D.wrapPointer(buffer, Box2D.b2Vec2);    shape.Set(ptr_wrapped, vertices.length);    return shape;}function createRandomPolygonShape(radius) {    var numVerts = 3.5 + Math.random() * 5;    numVerts = numVerts | 0;    var verts = [];    for (var i = 0; i < numVerts; i++) {        var angle = i / numVerts * 360.0 * 0.0174532925199432957;        verts.push( new b2Vec2( radius * Math.sin(angle), radius * -Math.cos(angle) ) );    }                return createPolygonShape(verts);}function getPointsByPolygonShape(fixture) {    var shape = fixture.GetShape();    var body = fixture.GetBody();    var polyShape = Box2D.castObject( shape, Box2D.b2PolygonShape );    if (polyShape == null) {        return [];    }    var count = polyShape.GetVertexCount();    var ret = [];    for (var i = 0; i < count; i++) {        var p = polyShape.GetVertex(i);        var pWorld = body.GetWorldPoint(p);        ret.push(new Vertex(pWorld.get_x(), pWorld.get_y()));    }     return ret;}function getPointsByPolygonBody(body) {    var ptr = body.GetFixtureList();    var arr = [];    while(ptr.e != 0) {        var vertices = getPointsByPolygonShape(ptr);        ptr = ptr.GetNext();        arr.push(vertices);    }    // var ret = mergeTwoSets(arr[0], arr[1]);    // for (var i = 2; i < arr.length; i++) {    //     ret = mergeTwoSets(ret, arr[i]);    // }    var first = arr.shift();    while (arr.length > 0) {        var i=0;        var merged = false;        for (; i < arr.length; i++) {            var beMerge = copyArr(arr[i])            var set = mergeTwoSets(first, beMerge);            if (set != null) {                first = set;                merged = true;                break;            }        }        arr.splice(i, 1);        if (!merged) {            break;        }    }    return first;}function mergeTwoSets(arr1, arr2) {    var a1, a2, b1, b2;    a1 = b2 = a2 = b1 = -1;    for (var i = 0; i < arr1.length; i++) {        var a = arr1[i];        for (var j = 0; j < arr2.length; j++) {            var b = arr2[j];            if (a.equals(b)) {                a1 = i;                a2 = i+1 >= arr1.length ? 0 : i+1;                b1 = j==0 ? arr2.length-1 : j-1;                b2 = j;                break;            }        }        if (a1 >= 0) {            break;        }    }    if (a1 < 0 || !arr1[a1].equals(arr2[b2]) || !arr1[a2].equals(arr2[b1])) {        return null;    }    for (var i = 0; i < b1; i++) {        arr2.push(arr2.shift());    }    arr2.splice(0, 2);    if (a2 == 0) {        return arr1.concat(arr2);    } else {        var arr3 = arr1.splice(a2, arr1.length-a2);        return arr1.concat(arr2).concat(arr3);    }}