Create a matrix, and use setMode(ControlP5.SINGLE_ROW) so that only one item per row can be selected.

It ignores this and works in the same way as if it was set to ControlP5.SINGLE_COLUMN.

The bug is trivial to fix in matrix.java, lines 148-158, check out the two loops below, they are exactly the same, whereas in single_row, it should clear the row not the column.

case (SINGLE_COLUMN): for (int i = 0; i < _myCellY; i++) { _myCells[tX][i] = 0; } _myCells[tX][tY] = (!isMarkerActive) ? 1 : _myCells[tX][tY]; break; case (SINGLE_ROW): for (int i = 0; i < _myCellY; i++) { _myCells[tX][i] = 0; } _myCells[tX][tY] = (!isMarkerActive) ? 1 : _myCells[tX][tY];

The single_row case should be for (int i = 0; i < _myCellX; i++) { _myCells[i][tX] = 0; }