Q68123: 7.10 "Subscript Out of Range," WindowDo with No Open Windows

Article: Q68123
Product(s): See article
Version(s): 7.00 7.10
Operating System(s): MS-DOS
Keyword(s): ENDUSER | SR# S901228-57 | mspl13_basic
Last Modified: 17-JAN-1991

If a WindowDo statement is executed before any windows are opened, a
"Subscript out of range" error will occur. This article explains why
the error happens and gives two ways of correcting the error.

This information applies to the User Interface (UI) ToolBox provided
with Microsoft BASIC Professional Development System (PDS) versions
7.00 and 7.10 for MS-DOS.

The problem is caused by WindowInit incorrectly initializing the
variable GloStorage.currMenu to -1 instead of 0 (zero). WindowDo
checks to see if currMenu is 0 (zero) to determine if there are no
open windows, and WindowDo generates the error when it tries to access
window number -1.

To work around this problem, do one of the following:

1. Open a window and then immediately close it. This will set currMenu
   back to 0 (zero). For example:

      WindowInit
      WindowOpen 1,6,5,12,25,0,7,0,7,15,FALSE,FALSE,FALSE,FALSE,0,""
      WindowClose 1
      WindowDo 0,0

2. To correct the problem permanently, modify WINDOW.BAS:

   a. Load the WINDOW.BAS module into QBX.EXE.

   b. Push F2 to view the subprograms and then move to WindowInit.

   c. Locate the line that reads "GloStorage.currMenu = -1", and change
      it to "GloStorage.currMenu = 0".

   d. Save the new copy of WINDOW.BAS. Then follow the instructions at
      the beginning of GENERAL.BAS to create a new LINK library (.LIB)
      and Quick library (.QLB).

Code Sample
-----------

When the following program is run in the QBX.EXE environment, it will
generate a "Subscript out of range in Quick library module: WINDOW"
error.

' QBX must be started with "QBX /L UITBEFR" to load the UI ToolBox
' Quick library

'$INCLUDE: 'general.bi'
'$INCLUDE: 'mouse.bi'
'$INCLUDE: 'menu.bi'
'$INCLUDE: 'window.bi'
COMMON SHARED /uitools/ GloMenu           AS MenuMiscType
COMMON SHARED /uitools/ GloTitle()        AS MenuTitleType
COMMON SHARED /uitools/ GloItem()         AS MenuItemType
COMMON SHARED /uitools/ GloWindow()       AS windowType
COMMON SHARED /uitools/ GloButton()       AS buttonType
COMMON SHARED /uitools/ GloEdit()         AS EditFieldType
COMMON SHARED /uitools/ GloStorage        AS WindowStorageType
COMMON SHARED /uitools/ GloWindowStack()  AS INTEGER
COMMON SHARED /uitools/ GloBuffer$()
DIM GloTitle(MAXMENU)           AS MenuTitleType
DIM GloItem(MAXMENU, MAXITEM)   AS MenuItemType
DIM GloWindow(MAXWINDOW)        AS windowType
DIM GloButton(MAXBUTTON)        AS buttonType
DIM GloEdit(MAXEDITFIELD)       AS EditFieldType
DIM GloWindowStack(MAXWINDOW)   AS INTEGER
DIM GloBuffer$(MAXWINDOW + 1, 2)
WindowInit
WindowDo 0,0
END

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