-- File:	TDF_Delta.cdl
--      	-------------
-- Author:	DAUTRY Philippe
--		<fid@fox.paris1.matra-dtv.fr>
---Copyright:	 MATRA DATAVISION 1997

---Version:	0.0
---History:	Version	Date		Purpose
--		0.0	Sep  8 1997	Creation


class Delta from TDF inherits TShared from MMgt

	---Purpose: A delta set is available at <aSourceTime>. If
	--          applied, it restores the TDF_Data in the state it
	--          was at <aTargetTime>.

uses

    OStream                  from Standard,
    ExtendedString           from TCollection,
    LabelList                from TDF,
    AttributeDelta           from TDF,
    AttributeDeltaList       from TDF

raises

    OutOfRange from Standard

is


    Create;
	---Purpose: Creates a delta.

    Validity(me : mutable;
    	     aBeginTime   : Integer from Standard;
    	     anEndTime    : Integer from Standard)
    	is protected;
	---Purpose: Validates <me> at <aBeginTime>. If applied, it
	--          restores the TDF_Data in the state it was at
	--          <anEndTime>. Reserved to TDF_Data.

    
    AddAttributeDelta (me : mutable;
    	    	       anAttributeDelta : AttributeDelta from TDF)
    	is protected;
	---Purpose: Adds an AttributeDelta to the list. Reserved to
	--          TDF_Data.

    IsEmpty (me) returns Boolean from Standard;
	---Purpose: Returns true if there is nothing to undo.
	--          
	---C++: inline    

    BeforeOrAfterApply(me; before : Boolean from Standard) is private;

    Apply (me : mutable) is private;
    
    IsApplicable (me; aCurrentTime : Integer from Standard)
    	returns Boolean from Standard;
	---Purpose: Returns true if the Undo action of <me> is
	--          applicable at <aCurrentTime>.
	-- 
	---C++: inline

    BeginTime (me) returns Integer;
	---Purpose: Returns the field <myBeginTime>.
	---C++: inline
    
    EndTime (me) returns Integer;
	---Purpose: Returns the field <myEndTime>.
	---C++: inline    

    Labels(me; aLabelList : in out LabelList from TDF);
	---Purpose: Adds in <aLabelList> the labels of the attribute deltas.
	--          Caution: <aLabelList> is not cleared before use.

    AttributeDeltas (me) returns AttributeDeltaList from TDF;
	---Purpose: Returns the field <myAttDeltaList>.
	---C++: inline    
	---C++: return const &

    Name(me) returns ExtendedString from TCollection;
   	---Purpose: Returns a name associated with this delta.
	---C++: inline   
    
    SetName(me : mutable; theName : ExtendedString from TCollection);
    	---Purpose: Associates a name <theName> with this delta
	---C++: inline


    Dump(me; OS : in out OStream from Standard);

fields

    myBeginTime    : Integer            from Standard;
    myEndTime      : Integer            from Standard;
    myAttDeltaList : AttributeDeltaList from TDF;
    myName         : ExtendedString     from TCollection;
    
friends

    class Data from TDF

end Delta;