[Development] binary compatibility promise

[Tony Van Eerd]

> -----Original Message-----
> [mailto:development-bounces+tvaneerd=rim.com at qt-project.org] On Behalf
> Of Ziller Eike
> 
> On 23 Nov 2012, at 11:20, Peter Hartmann <phartmann at rim.com> wrote:
> 
> >> Do you intend to upgrade this version of Qt that's installed on the
> device
> >> without upgrading the applications using it?
> >
> > yes, e.g. device updates and 3rd party apps in the store.
> 
> Well, even for device updates & 3rd party apps, the most sensible thing
> IMO is to provide a "beta period" for the device update to 3rd party
> app developers, so they can test their applications against the new
> versions and possibly update their application in the store.
> I mean there *are* behavior changes in every new version of Qt, also
> patch releases, that's what "bugfixing" is about ;). That might affect
> one or the other application in a negative way, in addition to the one
> or other bug that unfortunately gets introduced.
> 
> Regarding "can you run an application that was compiled against x.y.z
> also with x.y.(z-1)", I think that is simply a question of defining a
> policy. Also for shared Qt versions on devices, it is just a policy
> against which Qt version applications should be compiled to run on the
> wanted number of device installations.
> 

I *think* the plan is:

- there will be a single version of Qt 4.8.x shared by all apps on the device.
- that single version may be upgraded by RIM at some time (ie 4.8.y, doubtfully 4.9.z, not Qt5)
- there would be extensive in-house testing of the upgrade, including testing with a wide array of 3rd party apps
- Apps downloaded from AppWorld would not / could not upgrade the global installed Qt
- (apps can always ship their own "captive" version of Qt if they want, but that tends to just waste space) 

Eventually there should be a 5.x version of Qt, but that would be with a major platform upgrade - breaking BC not just with Qt, but with the BB libs,
and at which time both 4.8.x and 5.x would co-exist on the device (as well as coexisting versions of BB libs).

CAVEAT: I'm not in charge of this, and things can and do always change, but I think that's the general plan

Does that make sense to everyone?
Tony


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