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  The purpose of this compound widget is to provide an alternative
  to the DROPLIST widget offered in the IDL distribution. What has
  always annoyed me about a droplist is that you can't get the current
  "value" of a droplist easily. This compound widget makes this and
  other tasks much easier.


  David Fanning, Ph.D.
  1645 Sheely Drive
  Fort Collins, CO 80526 USA
  Phone: 970-221-0438
  E-mail: david@idlcoyote.com
  Coyote's Guide to IDL Programming: http://www.idlcoyote.com/


  General programming.

Calling Sequence

  droplistObj = FSC_Droplist(parent, Title='Animals: ", Value=['Dog'. 'Cat', 'Coyote'], Index=2)
  The return value of the FSC_Droplist (droplistObj in this example) is
  an object reference. Interaction with the droplist will occur through
  object methods.

Input Parameters

  parent -- The parent widget ID of the compound widget. Required.

Input Keywords

  Any keyword that is appropriate for the Widget_Droplist function can be used.
  In addition, these keywords are explicitly defined.
  EVENT_FUNC -- Set this keyword to the name of an Event Handler Function.
  EVENT_PRO -- Set this keyword to the name of an Event Handler Procedure.
  FORMAT -- A format specifier for the "format" of the values in the droplist.
  INDEX -- The index number of the current selection.
  SPACES -- A two-element array that indicates the number of blank spaces to be added
            to the the beginning and end of the formatted values. If a single number
            is provided, this number of blank spaces is added to both the beginning
            and the end of the value.
  TITLE -- The title of the droplist widget.
  UNAME -- The user name of the droplist widget. (Only available in IDL 5.2 and higher.)
  UVALUE -- The normal "user value" of the droplist.
  VALUE -- An array of the droplist "selections". May be any data type.

Common Blocks


Event Structure

  An event is returned each time the droplist value is changed. The event structure
  is defined like this:
  event = { FSC_DROPLIST_EVENT, $ ; The name of the event structure.
            ID: 0L, $ ; The ID of the compound widget's top-level base.
            TOP: 0L, $ ; The widget ID of the top-level base of the hierarchy.
            HANDLER: 0L, $ ; The event handler ID. Filled out by IDL.
            INDEX: 0L, $ ; The index number of the current selection.
            SELECTION:Ptr_New() $ ; A pointer to the current selection "value".
            SELF:Obj_New() } ; The object reference of the compound widget.
  GetID -- A function with no arguments that returns the widget identifier
      of the droplist widget.
      droplistID = droplistObj->GetID()
  GetIndex -- A function with no arguments that returns the index
      number of the current droplist selection.
      currentIndex = droplistObj->GetIndex()
  GetSelection -- A function with no arguments that returns the current
      droplist selection.
      currentSelection = droplistObj->GetSelection()
  GetUValue -- A function with no arguments that returns the "user value"
      of the compound widget i.e., the value set with the UVALUE keyword).
      myUValue = droplistObj->GetUValue()
  GetValues -- A function with no arguments that returns the "values" or
      "selections" for the droplist.
      possibleSelections = droplistObj->GetValues()
  Resize -- A procedure that sets the X screen size of the droplist. It is
      defined like this:
      PRO Resize, newSize, ParentSize=parentSize
      The "newSize" keyword is the new X screen size. If this argument is
      missing, the screen X size of the compound widget's parent is used.
      The parentSize keyword is an output keyword that returns the X screen
      size of the compound widget's parent.
      droplistObj->Resize, 400
      Note that not all devices (e.g., X Windows devices) support droplist resizing.
  SetIndex -- A procedure that sets the current droplist selection based on
      the given index. This is equivalent to Widget_Control, droplistID, Set_Droplist_Select=newIndex
      droplistObj->SetIndex, newIndex
  SetSelection -- Whereas a regular droplist widget can only be set by index
      number, this compound widget can also be set by a "selection". The new selection
      can be any data type and corresponds to one of the "values" of the droplist.
      droplistObj->SetSelection, newSelection
  SetValues -- Sets the possible selections of the droplist widget. The CurrentIndex keyword
      will allow the current index of the selection to be changed to:
      newChoices = ['dog', 'cat', 'coyote']
      droplistObj->SetValues, newChoices, CurrentIndex=2


  An example program is provided at the end of the FSC_DROPLIST code. To run it,
  type these commands:
      IDL> .Compile FSC_DROPLIST
      IDL> Example

Modification History

  Written by: David W Fanning, 17 Jan 2000. DWF.
  Added FORMAT and SPACES keywords 28 April 2000. DWF.
  Fixed a small problem with event processing when the EVENT_FUNC keyword
      was used. 29 Dec 2000. DWF.
  Attached the UNAME value to the TLB of the compound widget instead
      of to the droplist widget itself. 11 Jan 2001. DWF.
  Fixed a problem when the droplist was part of a modal widget and used the
      EVENT_PRO keyword. 27 Oct 2003. DWF.
  Added a SetValue method for setting all the values in the droplist at once. 12 Nov 2004. DWF.
  Fixed type on line 346/ 6 Feb 2008. DWF.

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