FSC_DROPLIST Name
FSC_DROPLIST Purpose
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. Author
FANNING SOFTWARE CONSULTING
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/
Category
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
None.
Dependencies
Requires ERROR_MESSAGE from the Coyote Library..
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.
PUBLIC OBJECT METHODS:
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
Example
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.