
<<File: DefaultNutUtilitiesImpl.mesa>>
<<CreatedBy: Butler on June 18, 1984 9:25:04 am PDT>>
<<Last Edited By:>>
<<Butler on  June 27, 1984 3:52:35 pm PDT>>
<<Widom on  June 18, 1984 9:25:39 am PDT>>
<<>>
<<>>
DIRECTORY
DB,
DefaultNutUtilities,
IO,
InputFocus,
Nut,
NutOps,
NutViewer,
ViewerOps,
Buttons;

DefaultNutUtilitiesImpl: CEDAR PROGRAM
IMPORTS
DB, Nut, NutOps, NutViewer, InputFocus, ViewerOps
EXPORTS DefaultNutUtilities =

BEGIN
OPEN DB, NutViewer;

SpawnParent: PROC[v: Viewer] RETURNS [parent: Viewer] = {
parent _ v; WHILE parent.parent # NIL DO parent _ parent.parent ENDLOOP };

ProcessSelection: PUBLIC Buttons.ButtonProc =
  -- A standard ButtonProc that assumes the button's REF ANY data is the FieldHandle above.
  -- Insures attribute of tuple is entity-valued and non-NIL, then calls Nut.Display on it.
  BEGIN OPEN DB;
  otherEntity: Entity;
  fd: DefaultNutUtilities.FieldHandle_ NARROW[clientData];
  viewer: Viewer_ NARROW[parent];
  IF fd.attribute=NIL THEN -- it was the relation itself
    { otherEntity _ RelationOf[fd.tuple];
      IF NOT DB.Null[otherEntity] THEN
       [] _ Nut.Display[eName: DB.NameOf[otherEntity], domain: "RelationDomain", parent: SpawnParent[viewer], segment: 
DB.SegmentOf[otherEntity]] }
  ELSE IF NutOps.EntityValued[fd.attribute] THEN -- attribute refs another entity
    IF Null[fd.tuple] THEN
      Message[viewer, "That relationship has been deleted!"]
    ELSE IF Null[otherEntity_V2E[GetF[fd.tuple, fd.attribute]]] THEN
      Message[viewer, "That entity has been deleted!"]
    ELSE
      { otherEntity _ V2E[GetF[fd.tuple, fd.attribute]];
        [] _ Nut.Display[eName: DB.NameOf[otherEntity], domain: DB.NameOf[DB.DomainOf[otherEntity]], parent: SpawnParent[viewer], 
segment: DB.SegmentOf[otherEntity]] }
  ELSE -- attribute is a string or number
    Message[viewer, "Not an entity-valued field"];
  END;

Reset: PUBLIC PROC[eName, domain: ROPE, seg: DB.Segment, viewer: Viewer] = 
BEGIN
-- Resets contents of editor to its statebefore edits started.
InputFocus.SetInputFocus[]; -- kill the caret
viewer.child _ NIL;
ViewerOps.PaintViewer[viewer, client];
[] _ Nut.Edit[eName: eName, domain: domain, segment: seg, parent: viewer] ;
END;

Edit: PUBLIC PROC[eName, domain: ROPE, seg: DB.Segment, parent: Viewer] = 
BEGIN
-- Invoked when hit the "Edit" button on the default displayer.
-- Should replace the displayer viewer with an editor viewer.
InputFocus.SetInputFocus[];
IF NutOps.IsSystemEntity[eName] THEN BEGIN
[] _ NutViewer.Message[NIL, eName, " is a system entity.  You may not edit it."];
RETURN;
END;
[] _ Nut.Edit[ eName: eName, domain: domain, segment: seg, parent: parent];
END;

END. . .