Split View Orientation

In AppKit, NSSplitView’s -isVertical/-setVertical: property refers to the orientation of the divider, not the axis on which the views are ordered. In other words, a split view with isVertical equal to YES has a leading view (on the left in locales that read left-to-right), and vertical dividers splitting subviews that are organized horizontally. A split view with isVertical equal to NO has a top view, and horizontal dividers splitting subviews that are organized vertically.

In Renaissance, set the isVertical property using the vertical attribute in the .gsmarkup file: set to YES for vertical dividers that organize subviews left-to-right, and NO for horizontal dividers that organize subviews top-to-bottom.