Mark Shuttleworth on the future of Ubuntu

Mark Shuttleworth on the future of Ubuntu

Posted Jun 5, 2008 8:52 UTC (Thu) by kripkenstein (subscriber, #43281)
In reply to: Mark Shuttleworth on the future of Ubuntu by and
Parent article: Mark Shuttleworth on the future of Ubuntu

Actually my point was that the existence of Vala is an indication that Gnome at least has deeper ties to Mono and C# than for example to Qt and C++ for some non-technical reason which is not obvious to me.

Actually this implies the opposite to me. The only similarity between Vala and Mono/C# is some of the syntax, and that's it (and while C# is a main source of inspiration for the syntax, so is Java, etc.). Vala doesn't use the Mono VM (or any VM), it doesn't use the .Net class library, and it's syntax is first and foremost meant to implement GObject conveniently. Also, if GNOME really liked Mono, it wouldn't bother with Vala. In fact Vala might seem at first antagonistic to Mono, which is why the Vala FAQ goes to great efforts to clarify that it's goal is not to duel with Mono.

(a) the generated code basically becomes unreadable by mere mortals, so using vala parts in C projects (and vince versa) is much harder than necessary

No, you should *never* need to look at the generated code (just as you don't look at generated assembler by GCC). When integrating Vala and C/GObject, you should have the files describing the API (.vapi, etc.), which describe the GObject overview, and are very clear and human-readable. You would use them. In fact one main goal of Vala, if not *the* goal, is to facilitate such convenient interoperability between Vala and C/GObject, e.g., writing libraries in Vala that are used by C/GObject, etc.

(b) what happens if the underlying C libraries (gtk, say) change their interfaces or even just the semantics? Then the vala to c translator always produces incorrect code which you can only fix by hacking the translator. this problem won't occur if the toolkit is used directly from within the language it is written in.

Well, if the interfaces change a little then the bindings for Vala need to change as well (the same goes for PyGTK). Note that you don't need to change the Vala compiler in this case, just the .vapi files that describe the language bindings. I guess in theory a more 'deep' change to GTK might necessitate changing the compiler - by a 'deep' change I mean one in which the semantics of GObject itself change - however, in that case you'd need to change C/GObject programs using GTK as well.

(d) to my knowledge it is very difficult to use debuggers such as gdb using vala's aproach since you would have to wade through the generated C code (on the other hand real programmers don't need debuggers anyway ;).

I agree with you, this is a very valid concern, it's a disadvantage of the approach. Perhaps in theory you might insert debug information that makes it better, but it'll never be quite as smooth as it should be. (And even debugging in C is cumbersome compared to debugging a VM-ed language like Python or Java.)

On the Qt/C++ side of the fence there has been (semi) automatic memory management by means of the Q*Pointer and various Container classes for an eternity (read: Qt 2.0), it has a nice foreach statement since 4.2 (IIRC), always had a very nice event notification mechanism and so on. Also you can use any C or C++ library out there without too much of a hassle. For all these reasons vala seems to be redundant from a technology perspective to me.

Ok, I am not up-to-date on the specifics of Qt, it seems. It sounds better than I thought. That said, it still isn't a good fit for GNOME, since it doesn't natively support the GObject system in its syntax, which is the whole purpose of Vala. Also, it's licensing is very different from the GNOME approach.

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> Ok, I am not up-to-date on the specifics of Qt, it seems. It sounds better    than I
thought. That said, it still isn't a good fit for GNOME, since it doesn't natively support the
GObject system in its syntax, which is the whole purpose of Vala. Also, it's licensing is very
different from the GNOME approach.

I always thought Gnome was started because Qt/Kde were not considered free enough. given the
fact that Qt is GPL and you're can use basically any other FOSS license in conjunction with Qt
as long as you keep providing the source, I don't get the point about licensing differences. I
think a free desktop should be all about free software and shouldn't worry too much about how
much proprietary developers have to pay for a development license. 

Maybe my original comment was also a bit ambiguous: I didn't argue in favour of Gnome dropping
GTK or anything, I just wanted to point out that for Gnome there is not much difference from
bundling C#/Mono apps from bundling Qt/C++ apps when it comes to technical considerations
(basically both live within their own separate ecosystem).In my opinion gnome should come with
a few Qt apps (also KDE should come with a few gtk apps, but that's a different story) if
these applications  blend sufficiently well into the 'alien' desktop environment... 

> The problem is that you can't use all the FOSS licenses, you depend on 
Nokia agreeing to your using them. For example, last I heard the AGPL 
wasn't permissible

Explicitly listing the AGPL is actually not necessary, since according to 

http://doc.trolltech.com/main-snapshot/license-gpl-except...

Qt is also licensed under GPLv3. In section 13 the GPLv3 states that "you 
have permission to link or combine any covered work with a work licensed 
under version 3 of the GNU Affero General Public License".

> Should Nokia become less cooperative than Trolltech has historically 
been, this might be very problematic.

this is true for any project which requires copyright assignments: 
OpenOffice and MySql come to mind. But they can't revoke the licensing of  
the current version including the GPL exception which means that they 
can't prevent forks. Also, there is still the QtFreeFoundation (or however 
it is was called again) which where is effectively controlled by the KDE 
community (KDE e.v ??) and has the right to release Qt under a BSD license 
if Trolltech "misbehaves". So, I really don't think there is any danger of 
losing the toolkit, not even for proprietary applications.

> I'm not familiar with MySQL, but OpenOffice is LGPL, not GPL;       
furthermore, OpenOffice is an app, not a framework like Qt. For both of       
these reasons I see little or no cause for concern if Sun should change       
OpenOffice's license to some other FOSS license. That is, if I want to       
write a plugin for OpenOffice using the GPL4, I will have no problem.        
       
if you are really this much concerned about not being able to use       
not-yet-existing OSS licenses and about being able to write proprietary    
derivate works without a payment, you really should be using a BSD instead    
of the linux kernel: Even if there  was desire to switch to GPLv3, linux    
is still stuck to the GPL v2 until _every_ contributor agreed on    
relicensing or alternatively every single line of code from authors who    
haven't agreed is removed.     
     
on the other hand you will always be able to use/fork/remix all versions  
of Qt with (A)GPLv(2|3) code and link it to any code which uses one of the       
licenses mentioned in Qt's GPL exception. Also if you want to use your 
code with a newer license you can still dual-license it. 

Actually the Linux kernel is close enough to what I want: I can write userspace apps using any
license and run them on the Linux kernel. It's like the LGPL in that respect. That is, only if
I want to extend the kernel itself do I have license issues - which is the same situation with
GTK+, which is LGPL.

In other words, that the Linux kernel stays GPL2 doesn't matter to me, unless I want to extend
the kernel itself. Same as with GTK (which is also GPL2 last I checked, and again, it doesn't
matter unless I extend GTK itself).

This is the reason I prefer GTK and the Linux kernel's approach to licensing over Qt's (for
libraries/frameworks, at least. For normal apps, other licenses might be better).