Debug.fillRect(bestPos.delta + maskEdgeL, 0, 1, backCanvasForDebug.height);
                            backContextForDebug.fillRect(bestPos.delta + maskEdgeR, 0, 1, backCanvasForDebug.height);
                            backContextForDebug.fillRect(0, maskEdgeT + offsetT, backCanvasForDebug.width, 1);
                            backContextForDebug.fillRect(0, maskEdgeB + offsetT, backCanvasForDebug.width, 1);
                        }

                        return bestPos.delta + offsetL;
             