Bizarre cursor behavior (OpenInsight 32-bit Specific) [Revelation On-Line Wiki]

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==== Bizarre cursor behavior (OpenInsight 32-bit Specific) ====
=== At 21 AUG 2003 12:28:15PM Gerald Lovel wrote: ===
 
{{tag>"OpenInsight 32-bit Specific"}}
 
<QUOTE>
I have an MDI frame with child windows A and B. Window A browses cursor 1 showing records from table A. Window B browses cursor 2 showing records from table B.



From window A, I wish to use the active cursor temporarily in some other process, say a viewer popup. So I make a temporary copy of the cursor with the following code:



	TempCursor=0

	ClearSelect TempCursor

	Select.Seek( Seek$Top, Cursor, 0, Flag )

	Swap.Cursor( Cursor, TempCursor, Swap$Copy )

	... (temporary process follows)



Where, Cursor=1, Seek$Top=0, and Swap$Copy=2. When the temporary process finishes, I continue to browse cursor 1 in window A without problems.



Next I change focus to window B, where cursor 2 is active, and the correct list is being browsed. Again, I call my temporary process code, where this time cursor=2.



After which, I discover that Window B is browsing keys from cursor 1, table A. Woah, Nelly! What happened here?



(Questions or comments about the Select.Seek and SwapCursor routines are welcome.)



Gerald

glovel@wares.cc
</QUOTE>
----

=== At 24 AUG 2003 03:06PM Gerald Lovel wrote:  ===

<QUOTE>Did some more testing on this. Started windows A and B. Performed a select into cursor 0 in window A, and used SWAP.CURSOR to copy the results into cursor 1. Switched to window B. Cleared cursor 0, performed a select into cursor 0, and used SWAP.CURSOR to copy the results into cursor 2.



I can tell you that window A, browsing cursor 1, loses its list when any other process clears or uses cursor 0. Therefore SWAP.CURSOR is moving the pointers around in @CURSORS, but the internals where the key list resides is still associated with cursor 0. If SWAP.CURSOR could really move a cursor pointer and its list from 0 to another cursor, it would be very nice.



Many commands work with cursor 0 only. This is actually a good thing, because cursor 0 always terminates when BASIC exits. So if you need a temporary cursor for a command or a BASIC routine, you can be assured that cursor 0 is available (until BASIC becomes multithreaded?). But once a select or list operation which is limited to cursor 0 returns a cursor, there needs to be a way to pass that cursor on to a persistent process such as a window. Making a cursor persistent means transferring ALL its information into the new cursor, not just SOME of the pointers.



Of course, I can use my CURSOR2LIST routine to make a key list from from the cursor (ugh). Somehow my enthusiasm for this solution is limited. Any reason why SWAP.CURSOR can't be made to work?



Gerald

</QUOTE>


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