Bug 1803, Upcoming breaking changes for 4.10.0-beta1

[Steve Lime]

+1 from me too. The nice thing it's a beta release so there's still time
if we
find we've overstepped a boundary. This is good discussion and I want
to 
thank Tamas for the investigative work and solution (and Umberto for
taking
time from vacation - you're more generous than I!)...

Steve

>>> Daniel Morissette <dmorissette at MAPGEARS.COM> 8/17/2006 4:03:53 PM
>>>
After a bit more thinking and discussion on IRC, I am with Steve and 
also think that all the members that are listed in Steve's email can 
safely be made immutable since it would not make sense to attempt to 
overwrite them anyway. (That's also the way things are in PHP MapScript

and that never stopped us from doing anything).

With respect to imageObj.format, I think it should be made read-only or

hidden since we get an imageObj from methods that create the actual 
image, and changing the outputFormatObj on the image after it's been 
created is just asking for trouble (not to mention the possible object

referencing issues that Tamas is trying to address).

I give my +1 to go ahead with this.

Also please make sure you include a note listing the members that were

made immutable in HISTORY.TXT.

Daniel

Steve Lime wrote:
> Umberto: How do you add classes and layers at runtime? In the context
of
> a layer or a map
> correct? I don't believe that what Tamas is proposing would change
that
> capability at all. 
> 
> If you look at the list:
> 
> classObj.layer
> webObj.map
> legendObj.map
> layerObj.map
> 
> are back references and you don't want folks monkeying around with
> them.
> 
> classObj.label
> legendObj.label
> mapObj.scalebar
> mapObj.legend 
> mapObj.querymap
> mapObj.web
> mapObj.symbolset
> mapObj.labelcache
> mapObj.reference
> 
> Already exist in their parent objects so there is no need to create
new
> ones in place of the
> existing ones. Users should get the reference to the existing
structure
> and modify it in place.
> I'm not sure that given the potential problems that it even makes
sense
> to have constructors
> for these. I assume this is the contentious spot...
> 
> (If there is a glaring need to have, for example, an unattached 
> labelObj laying around then 
> couldn't a populateFrom capability be developed for a labelObj, or
> perhaps setLabel() for a
> classObj?)
> 
> classObj.metadata
> fontSetObj.fonts
> mapObj.configoptions
> webObj.metadata
> 
> Are hash tables and Sean created a nice interface for them to use.
> Modifying directly shouldn't
> be allowed. I think this is what was ok'd yesterday.
> 
> Note sure about  imageObj.format...
> 
> I guess I don't see the big deal with this change. My 2 cents. 
> 
> Steve
> 
> 
>>>>Umberto Nicoletti <umberto.nicoletti at GMAIL.COM> 8/17/2006 8:25 AM
>>>>
> 
> On 8/17/06, Daniel Morissette <dmorissette at mapgears.com> wrote:
> 
>>Tamas Szekeres wrote:
>>
>>>>I think you can safely hide the labelPathObj, that should not be
>>>>exposed. I think the others
>>>>should be immutable too (assuming I understand the problem
> 
> correctly),
> 
>>>>the question is how
>>>>many scripts will the change break and should backward
> 
> compatability
> 
>>>>breakage be limited
>>>>to major releases (e.g. 5.0).
>>>>
>>>
>>>Those scripts are *erroneous* !  It would be desirable to force
> 
> the
> 
>>>users to put them into a good shape as soon as possible.
>>>
>>>
>>
>>It seems that I should take position as release manager but
>>unfortunately I do not know or use SWIG MapScript much so I have to
> 
> rely
> 
>>on those who know to make an opinion on whether the current stuff is
>>dangerous enough to warrant breaking a few scripts with 4.10.
>>
>>Based on the understanding I have of the problem from reading this
>>thread and previous discussions, it seems to me that if those
> 
> scripts
> 
>>are doing something that is just waiting to bomb then changing SWIG
>>MapScript in v4.10 to make those object references immutable is not
> 
> a
> 
>>backwards compatibility issue, it is a bugfix and a service we are
>>making to those users by forcing them to fix their scripts... and in
> 
> the
> 
>>end their apps will just be more robust.
>>
> 
> 
> Daniel,
> IMO  we are talking about fixing pieces of code we are not even sure
> they are broken. For instance I have some Java mapscript tests (and
an
> application) running just fine that add layers and classes at run
time
> and that's why I am so reluctant in approving this proposal. Only
once
> we get a test case that reproduces this errors reliably then we can
go
> and change the code.
> 
> Unfortunately I couldn't join the IRC meeting because I am on
vacation
> otherwise I'd have spoken  earlier (I am writing this on the road).
> 
> Regards,
> Umberto
> 
> 
>>The real question that I would throw at the SWIG MapScript experts
> 
> is:
> 
>>"Is the practice of overwriting those object references really
> 
> dangerous
> 
>>or not?"
>>
>>If the answer is yes then I think that solves the question and we
> 
> need
> 
>>to apply the fix and force users to fix their scripts.
>>
>>If there are object references that can safely be overwritten (such
> 
> as
> 
>>colorObj) then my opinion is that we should not touch them in 4.10.
>>
>>Daniel
>>--
>>Daniel Morissette
>>http://www.mapgears.com/ 
>>
> 
> 


-- 
Daniel Morissette
http://www.mapgears.com/