New way to modify nested uno structs in LibreOffice BASIC

[Andrew Douglas Pitonyak]

On 07/04/2012 03:23 PM, Noel Power wrote:
> with 
> http://cgit.freedesktop.org/libreoffice/core/commit/?id=1720641bf36306fc296635925e571556ced8a302 
> a long standing wrinkle with modifying nested structs in basic should 
> be eliminated
>
> before this change the following macro snippet would not work.
>
>    Dim b0 as new "com.sun.star.table.TableBorder"
>    MsgBox b0.HorizontalLine.OuterLineWidth 'HorizontalLine member is 
> itself a "com.sun.star.table.BorderLine" struct
>    b0.HorizontalLine.OuterLineWidth = 9
>    'the following line unexpectedly displays '0' because 
> 'b0.HorizontalLine' returns a new but temporary copy of 
> "com.sun.star.table.BorderLine"
>    MsgBox b0.HorizontalLine.OuterLineWidth
>
> the unfortunate non obvious workaround to modify the contents of 
> 'b0.HorizontalLine.OuterLineWidth' is....
>    a) create a new "com.sun.star.table.BorderLine" instance
>    b) clone it with the contents of 'b0.HorizontalLine'
>    c) modify the 'OuterLineWidth' member of the new 
> "com.sun.star.table.BorderLine" instance
>    d) set the value b0.HorizontalLine' with the newly modified 
> "com.sun.star.table.BorderLine" instance
>
> Although I have test this pretty well [*]  ( and fixed lots of issues 
> already before committing ) changes to the basic runtime are always 
> perilous ;-) so.. please please be on the lookout for any strange 
> behaviour regarding handling of uno structs in basic
>
> Noel
>
> [*] have to admit I only tested one level of indirection. I didn't 
> find a suitable structure that contains a structure that contains a 
> structure to test, if you know of one off hand let me know :-) Also I 
> have yet to write some unit tests for this ( but will do )
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>

The behavior change scares me a bit. I seem to remember some time back 
that there was a reason for this behavior, but I was given that 
information many years back..... I discussed it in Berlin

http://www.pitonyak.org/oooconf/OOoConf_2004_Macro_Presentation.sxi

Do you intend to change UNO so that structures return as a reference 
(very dangerous, don't do it), or only when used in basic as 
object.structure.property? This may be workable / safe, but may break 
some existing code (although I can't think of any code that it would break).


I feel silly asking this, since if you know how to change the behavior, 
then you likely know more about this than I (I don't know how to change 
the behavior).

-- 
Andrew Pitonyak
My Macro Document: http://www.pitonyak.org/AndrewMacro.odt
Info:  http://www.pitonyak.org/oo.php