PlacementOption enum

The PlacementOption enum is recommended as the means for using descriptive names when testing condition bits in the .Status values of a RtValue object.
Example 
enum PlacementOption {
    Default		= 0,  // built-in Display placement in Layout rules
    TriggerPoint,
    DisplayFrame,       // opens pop-up within a Display Frame
    Screen,
    NearRegion,
    AboveRegion,
    BelowRegion,
    LeftOfRegion,
    RightOfRegion,
    FullDisplayFrame,	// replaces current Display in Display Frame
                        // designated by Placement.ReferenceName
}
PlacementOption.FullDisplayFrame works only with displays because contextual displays always open as popups. To open a popup (either a contextual display or display) relative to a display frame, use PlacementOption.DisplayFrame. You can also provide an alignment option to tell the popup where in the display frame to open.
Example
Example Result 
var placement = new Types.Placement({Option: Constants.PlacementOption.DisplayFrame, ReferenceName: "Main2", Alignment: Constants.PlacementAlignment.Centered});
DL.OpenContextDisplayAsync("CDisplay1", "", [placement]);
 Opens CDisplay1 as a popup centered over the display frame, Main2. 
var placement = new Types.Placement({Option: Constants.PlacementOption.FullDisplayFrame, ReferenceName: "Main2"});
DL.OpenDisplayAsync("Display1", [placement]);
 Opens Display1 in the display frame, Main2.