var dom = fw.getDocumentDOM();
var sel = [].concat(fw.selection);

function TileSelection(){
	if(!dom) return;
	
	var MAX_WIDTH = dom.width;
	var elems = [].concat(sel), newElems = [];
	
	// use all elements in document if none are selected
	if(!sel.length){
		elems = [];
		for(var l in dom.layers){
			for(var e in dom.layers[l].frames[dom.currentFrameNum].elements){
				if(dom.layers[l].frames[dom.currentFrameNum].elements[e].visible)
					elems.push(dom.layers[l].frames[dom.currentFrameNum].elements[e]);
			}
		}
	}
	
	// tile algorithm - create a grid and find grid spots that elements fit it
	var GRID_SIZE = 10/*MAX_WIDTH/100*/, COLUMNS = Math.floor(MAX_WIDTH/GRID_SIZE), rows = [], r, c;
	var elem, gridW, gridH, grid;
	for(var e=0; e<elems.length; e++){
		elem = elems[e];
		gridW = Math.max(1,Math.ceil(elem.width/GRID_SIZE));
		gridH = Math.max(1,Math.ceil(elem.height/GRID_SIZE));
		// skip elements that are larger than the canvas
		if(gridW > COLUMNS) continue;
		// find the first open grid slot
		grid = findGrid(gridW,gridH);
		fw.selection = elem;
		dom.moveSelectionTo({x:grid.c*GRID_SIZE,y:grid.r*GRID_SIZE},false,false);
		newElems.push(fw.selection[0]);
	}
	fw.selection = newElems;
	return true;
	
	// find an open spot in the grid
	function findGrid(w,h){
		var r = 0, c = 0, currW, currH;
		// looping through rows, no limit
		while(true){
			currW = currH = 0;
			// create new blank grid row if necessary
			if(!rows[r])
				rows[r] = new Array(COLUMNS);
			
			// loop through columns in current row
			for(c=0; c<COLUMNS; c++){
				// count any open grid slots
				if(!rows[r][c])
					currW++;
				else
					currW = 0;
				if(currW >= w){
					// enough empty columns foind in row (width)
					// check for available columns [height] rows above
					currH = 0;
					while(currH < h){
						currH++;
						if(!rows[r+currH]) return returnGrid('new row');
						for(var i=0; i<w; i++){
							if(rows[r+currH][c-i])
								break;
						}
						//if(elem.name == 'poo') alert([currH,h,i,w])
						if(currH == h && i==w){
							return returnGrid('clear height');
						}else if(i!=w){
							currW = 0;
							//c = c-(currW-1)+1;
							//currW = 1;
							break;
						}
					}
				}
			}
			r++;
			//if(r>100) return {r:-99,c:-99} // dev - prevent endless loop
		}
		// function to mark the current grid slots as taken and return grid location
		function returnGrid(msg){
			//elem.name = msg;
			for(var i=0; i<h; i++){
				// create rows
				if(!rows[r+i])
					rows[r+i] = new Array(COLUMNS);
				
				// clear columns in those rows are used (true)
				for(var j=0; j<w; j++){
					if(rows[r+i][c-j]) createTile(r+i,c-j,String([r+i,c-j]))
					rows[r+i][c-j] = true;
				}
			}
			return {r:r,c:c-(w-1)};
		}
		function createTile(r,c,n){
			dom.addNewRectangle({left:c*GRID_SIZE,right:(c*GRID_SIZE)+GRID_SIZE,top:r*GRID_SIZE,bottom:(r*GRID_SIZE)+GRID_SIZE},0);
			dom.setOpacity(50);
			fw.selection[0].name = n;
		}
	}
}

try{
TileSelection();
}catch(e){ alert([e, e.lineNumber, e.fileName].join("\n")) };