// Associates the given window with window 2, drawing the appropriate sash
// and changing the split mode.
// Associates the given window with window 2, drawing the appropriate sash
// and changing the split mode.
// A sashPosition of 0 means choose a default sash position,
// negative sashPosition specifies the size of right/lower pane as it's
// absolute value rather than the size of left/upper pane.
// A sashPosition of 0 means choose a default sash position,
// negative sashPosition specifies the size of right/lower pane as it's
// absolute value rather than the size of left/upper pane.