actionscript 3 - customer layout with drag-drop support -

evtim wrote greate customer flowlayout, , maxim have nice customer horizontal multiline layout don't support drag-drop. when define customer layout extends layoutbase drag-drop supporting, user should implements or override functions?

i had worked out, following customer layout based on horizontal multiline layouy of maxim:

public class horizontalmultilinelayout extends layoutbase {         private var _rowcount:int = -1;         private var _columncount:int = -1;          //container width         private var lastwidth:number = -1;          private var _horizontalgap:number = 6;          public function horizontalgap():number         {             return _horizontalgap;         }          public function set horizontalgap(value:number):void         {             if (value == _horizontalgap)                 return;              _horizontalgap = value;             invalidatetargetsizeanddisplaylist();         }          private var _verticalgap:number = 6;          public function verticalgap():number         {             return _verticalgap;         }          public function set verticalgap(value:number):void         {             if (value == _verticalgap)                 return;              _verticalgap = value;             invalidatetargetsizeanddisplaylist();         }          private var _verticalalign:string = verticalalign.top;          [inspectable(category="general", enumeration="top,bottom,middle", defaultvalue="top")]         public function verticalalign():string         {             return _verticalalign;         }          public function set verticalalign(value:string):void         {             if (_verticalalign == value)                 return;              _verticalalign = value;             invalidatetargetsizeanddisplaylist();         }          private var _paddingleft:number = 0;          public function paddingleft():number         {             return _paddingleft;         }          public function set paddingleft(value:number):void         {             if (_paddingleft == value)                 return;              _paddingleft = value;             invalidatetargetsizeanddisplaylist();         }              private var _paddingright:number = 0;          public function paddingright():number         {             return _paddingright;         }          public function set paddingright(value:number):void         {             if (_paddingright == value)                 return;              _paddingright = value;             invalidatetargetsizeanddisplaylist();         }              private var _paddingtop:number = 0;          public function paddingtop():number         {             return _paddingtop;         }          public function set paddingtop(value:number):void         {             if (_paddingtop == value)                 return;              _paddingtop = value;             invalidatetargetsizeanddisplaylist();         }              private var _paddingbottom:number = 0;          public function paddingbottom():number         {             return _paddingbottom;         }          public function set paddingbottom(value:number):void         {             if (_paddingbottom == value)                 return;              _paddingbottom = value;             invalidatetargetsizeanddisplaylist();         }              override public function measure():void         {             if (lastwidth == -1) {                 return;             }              var measuredwidth:number = 0;             var measuredminwidth:number = 0;             var measuredheight:number = 0;             var measuredminheight:number = 0;              var layouttarget:groupbase = target;             var n:int = layouttarget.numelements;             var element:ilayoutelement;             var i:int;             var width:number = layouttarget.explicitwidth;             if (isnan(width) && lastwidth != -1)                 width = lastwidth;             if (isnan(width)) // width not defined parent or user             {                 // not specify measuredwidth , measuredheight real                 // values because in fact can layout @ width or height                 (i = 0; < n; i++)                 {                     element = usevirtuallayout ? layouttarget.getvirtualelementat(i) : layouttarget.getelementat(i);                     if (!element || !element.includeinlayout)                         continue;                      measuredwidth = math.ceil(element.getpreferredboundswidth());                     measuredheight = math.ceil(element.getpreferredboundsheight());                     break;                 }                 measuredminwidth = measuredwidth;                 measuredminheight = measuredheight;             }             else             {                 // calculate lines based on width                 var currentlinewidth:number = 0;                 var currentlineheight:number = 0;                 var linenum:int = 1;                 (i = 0; < n; i++)                 {                     element = usevirtuallayout ? layouttarget.getvirtualelementat(i) : layouttarget.getelementat(i);                     if (!element || !element.includeinlayout)                         continue;                      var widthwithoutpaddings:number = width - _paddingleft - _paddingright;                     var elementwidth:number = math.ceil(element.getpreferredboundswidth());                     if (currentlinewidth == 0 ||                          currentlinewidth + _horizontalgap + elementwidth <= widthwithoutpaddings)                     {                         currentlinewidth += elementwidth + (currentlinewidth == 0 ? 0 : _horizontalgap);                         currentlineheight = math.max(currentlineheight, math.ceil(element.getpreferredboundsheight()));                     }                     else                     {                         measuredheight += currentlineheight;                          linenum++;                         currentlinewidth = elementwidth;                         currentlineheight = math.ceil(element.getpreferredboundsheight());                     }                 }                 measuredheight += currentlineheight;                 if (linenum > 1)                     measuredheight += _verticalgap * (linenum - 1);                  // not set measuredwidth real value because can                   // layout @ width                 (i = 0; < n; i++)                 {                     element = usevirtuallayout ? layouttarget.getvirtualelementat(i) : layouttarget.getelementat(i);                     if (!element || !element.includeinlayout)                         continue;                      measuredwidth =                         measuredminwidth = math.ceil(element.getpreferredboundswidth());                     break;                 }                 measuredminheight = measuredheight;             }              layouttarget.measuredwidth = measuredwidth + _paddingleft + _paddingright;             layouttarget.measuredminwidth = measuredminwidth + _paddingleft + _paddingright;             layouttarget.measuredheight = measuredheight + _paddingtop + _paddingbottom;             layouttarget.measuredminheight = measuredminheight + _paddingtop + _paddingbottom;         }          override public function updatedisplaylist(width:number, height:number):void         {             resetrowandcolumn();             var layouttarget:groupbase = target;             var n:int = layouttarget.numelements;             var element:ilayoutelement;             var i:int;             // calculate lines based on width             var x:number = _paddingleft;             var y:number = _paddingtop;             var maxlineheight:number = 0;             var elementcounter:int = 0;             var positions:vector.<point> = new vector.<point>();             (i = 0; < n; i++)             {                 element = usevirtuallayout ? layouttarget.getvirtualelementat(i) : layouttarget.getelementat(i);                 if (!element || !element.includeinlayout)                     continue;                  var elementwidth:number = math.ceil(element.getpreferredboundswidth());                 if (x == _paddingleft || x + _horizontalgap + elementwidth <= width - _paddingright) {                     if (elementcounter > 0)                         x += _horizontalgap;                     positions[i] = new point(x, y);                     element.setlayoutboundssize(nan, nan);                     maxlineheight = math.max(maxlineheight, math.ceil(element.getpreferredboundsheight()));                     //calculate column count                     if(!startnewline) {                         _columncount++;                     }                 }else {                     startnewline = true;                     _rowcount++;                     x = _paddingleft;                     y += _verticalgap + maxlineheight;                     maxlineheight = math.ceil(element.getpreferredboundsheight());                     positions[i] = new point(x, y);                     element.setlayoutboundssize(nan, nan);                 }                 x += elementwidth;                 elementcounter++;             }              // verticalalign , setlayoutboundsposition() elements             var yadd:number = 0;             var ydifference:number = height - (y + maxlineheight + _paddingbottom);             if (_verticalalign == verticalalign.middle)                 yadd = math.round(ydifference / 2);             else if (_verticalalign == verticalalign.bottom)                 yadd = math.round(ydifference);             (i = 0; < n; i++)             {                 element = usevirtuallayout ? layouttarget.getvirtualelementat(i) : layouttarget.getelementat(i);                 if (!element || !element.includeinlayout)                     continue;                 var point:point = positions[i];                 point.y += yadd;                 element.setlayoutboundsposition(point.x, point.y);             }              // if width changed height change - remeasure             if (lastwidth == -1 || lastwidth != width)             {                 lastwidth = width;                 invalidatetargetsizeanddisplaylist();             }             //trace("rowcount: ---", _rowcount, " ---columncount: ----", _columncount);         }          private var startnewline:boolean = false;          private function resetrowandcolumn():void {             var num:int = target.numelements;             if(num >0) {                 _rowcount = 1;                 _columncount = 0;             } else {                 _rowcount = _columncount = 0;             }             startnewline = false;         }          private function invalidatetargetsizeanddisplaylist():void         {             var g:groupbase = target;             if (!g)                 return;              g.invalidatesize();             g.invalidatedisplaylist();         }          private function calculatedropcellindex(x:number, y:number):array {             var xstart:number = x - paddingleft;             var ystart:number = y - paddingtop;             var column:int = math.floor(xstart / (columnwidth + _horizontalgap));             var row:int = math.floor(ystart / (rowheight + _verticalgap));              // check whether x closer left column or right column:             var midcolumnline:number;             var midrowline:number;              midcolumnline = (column + 1) * (columnwidth + _horizontalgap) - _horizontalgap - columnwidth / 2;               // mid-line @ middle of gap between rows             midrowline = (row + 1) * (rowheight + _verticalgap) - _verticalgap / 2;                if (xstart > midcolumnline)                 column++;             if (ystart > midrowline)                 row++;              // limit row , column, if 1 far drop location             // , there white space             if (column > _columncount || row > _rowcount)             {                 row = _rowcount;                 column = _columncount;             }              if (column < 0)                 column = 0;             if (row < 0)                 row = 0;              if (row >= _rowcount)                 row = _rowcount - 1;              return [row, column];         }          override protected function calculatedropindex(x:number, y:number):int {             var result:array = calculatedropcellindex(x, y);             var row:int = result[0];              var column:int = result[1];              var index:int = row * _columncount + column;             var count:int = target.numelements;              if (index > count) {                 index = count;             }              return index;         }          private function columnwidth():number {             return typicallayoutelement.getlayoutboundswidth();         }          private function rowheight():number {             return typicallayoutelement.getlayoutboundsheight();         }          //note:we not use contentwidth         override protected function calculatedropindicatorbounds(droplocation:droplocation):rectangle {             var result:array = calculatedropcellindex(droplocation.droppoint.x, droplocation.droppoint.y);             var row:int = result[0];              var column:int = result[1];               var count:int = target.numelements;              // last row may partially full,             // don't drop beyond last column.             if (row * _columncount + column > count)                 column = count - (_rowcount - 1) * _columncount;              var x:number;             var y:number;             var dropindicatorelement:ivisualelement;             var emptyspace:number; // empty space between elements              // start dropindicator dimensions, in case it's not              // ivisualelement             var width:number = dropindicator.width;             var height:number = dropindicator.height;              emptyspace = (0 < _horizontalgap ) ? _horizontalgap : 0;              var emptyspaceleft:number = column * (columnwidth + _horizontalgap) - emptyspace;              // special case - if have negative gap , we're last column,             // adjust emptyspaceleft             if (_horizontalgap < 0 && (column == _columncount || count == droplocation.dropindex))                 emptyspaceleft -= _horizontalgap;              width = emptyspace;             height = rowheight;             // special case - if have negative gap , we're not last             // row, adjust height             if (_verticalgap < 0 && row < _rowcount - 1)                 height += _verticalgap + 1;              if (dropindicator ivisualelement)             {                 dropindicatorelement = ivisualelement(dropindicator);                 width = math.max(math.min(width,                     dropindicatorelement.getmaxboundswidth(false)),                     dropindicatorelement.getminboundswidth(false));             }              x = emptyspaceleft + math.round((emptyspace - width) / 2) + paddingleft;             // allow 1 pixel overlap container border             //x = math.max(-1, math.min(target.contentwidth - width + 1, x));             //note:we not use contentwidth             x = math.max(-1, math.min(target.width - width + 1, x));             y = row * (rowheight + _verticalgap) + paddingtop;             return new rectangle(x, y, width, height);         }  }