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Implementation of Read-Only List Boxes in a Presentation Manager Application

IP.com Disclosure Number: IPCOM000114239D
Original Publication Date: 1994-Nov-01
Included in the Prior Art Database: 2005-Mar-28
Document File: 2 page(s) / 97K

Publishing Venue

IBM

Related People

Johnson, DK: AUTHOR [+4]

Abstract

List boxes are an integral control in most OS/2* Presentation Manager* (PM) applications. Lists allow the user to see all of the available choices for a given item, and to select those that are appropriate for the current situation.

This text was extracted from an ASCII text file.
This is the abbreviated version, containing approximately 52% of the total text.

Implementation of Read-Only List Boxes in a Presentation Manager
Application

      List boxes are an integral control in most OS/2* Presentation
Manager* (PM) applications.  Lists allow the user to see all of the
available choices for a given item, and to select those that are
appropriate for the current situation.

      However, lists should also be able to serve the function of
displaying to the user the current state of the environment, without
allowing the user to change the selections in the list.  These lists
are read-only lists, and should allow full user interaction with the
exception of the user not being able to change which items are
selected in the list.

      The problem exists that PM does not provide a list style of
read-only.  All PM lists either allow the user to change the selected
items, or else are disabled.  Disabled lists do not allow the list to
receive the focus, and thus the user can not get help information
about the list.  Disabled lists are also not scrollable, thus not
allowing the user to see all of the items in the list.

      It therefore becomes the application's responsibility to
implement lists that allow the user all of the navigation techniques
he or she has come to expect, and to receive the focus, without
allowing the user to change the selections.  The list also must have
a different appearance than a standard list to provide the user
visual feedback as to which type of list it is.  This disclosure
describes how an application can implement read-only lists and how
this visual distinction can be supplied.

      The key to converting a standard list to a read-only list is
handling all of the messages that are used to navigate through the
list and select list items.  These keystroke and mouse combinations
have different effects depending on what type of list it is.  Lists
can be single select lists, multiple select lists or extended select
lists.  Each of these follows its own selection and navigation
conventions, as defined by the Common User Access* (CUA) standards.

When a list is converted to be read-only, it should still follow the
same same navigation conventions.  The only change should be that the
actions will not change the selected list items.

      Regardless of the list type, navigation and selection are
always keyed to keystroke input and mouse input.  When the relevant
messages are received, they should do everything they normally do
except change the selected items.  The messages that need to be
handled are:
  o  WM_CHAR These messages communicate the keystroke combinations
      that the user uses to work with th...