[Qt-interest] Licensing

[Finley Lee]

It is also difficult to use Qt in a plug-in for a Windows application.  I'm talking about plug-ins for applications like web browsers and image editors, not Qt plug-ins.

If you want to use a shared build of Qt in this situation, you can put your DLLs in one of three places:

* Install them in the path.  This may be the best choice but you have to make sure your DLL names won't conflict with other builds of Qt.  I believe the 'infix' config option can help with this.  If the path changes your application can break.  Also, if you have lots of plug-ins using different versions of Qt, you'll end up with a confusing jumble of files.

* Install in \Windows\System32 or \Windows\System.  I believe Microsoft recommends against this, but it could work.  The same concerns as putting the Qt DLLs in the path apply.

* Install next to the host application's binary.  This isn't a good choice because there may be multiple host application that use the same plug-in.  Also, it seems like an unsafe practice to put any files at all in another vendors application directory.  Your application can break if the user installs a new plug-in host.  

I'd prefer to be able to install the Qt DLLs in the same folder as the plug-in, but without SxS I'm not sure how this could work.  I ended up buying a commercial license in order to link to Qt statically.

--
Finley Lee
Alien Skin Software


-----Original Message-----
From: qt-interest-bounces at trolltech.com [mailto:qt-interest-bounces at trolltech.com] On Behalf Of Jason H
Sent: Thursday, June 03, 2010 4:46 PM
To: Thiago Macieira; qt-interest at trolltech.com
Subject: Re: [Qt-interest] Licensing

There is one place where the .DLLs are not always possible.

That is as a Windows Service using the QtService solution. Those DLLs need to be in the system PATH or the system directories. If you have multiple services using Qt, and they need specific versions you can find yourself in DLL hell. The only way is to statically link Qt in. There may be a way to use the SxS/Manifest file stuff in VS2005+ to fix it, but I don't know how at this time. 




----- Original Message ----
From: Thiago Macieira <thiago at kde.org>
To: qt-interest at trolltech.com
Sent: Thu, June 3, 2010 9:57:51 AM
Subject: Re: [Qt-interest] Licensing

Em Quinta-feira 03 Junho 2010, às 14:44:55, Scott Aron Bloom escreveu:
> My basic view is this, when Nokia made this decision to go LGPL, they
> must have had an expectation in mind of how closed source developers
> would use the license, a preferred way if you will.  My plea, is just
> document that preferred way, and let us developers follow it.

In order of preference, we'd like:

1) that you release the sources
2) link dynamically

That doesn't mean they're the only available options to you. But we clearly 
prefer that you link dynamically. Then we have nice libQtCore.so or 
QtCore4.dll files around in your app :-)

-- 
Thiago Macieira - thiago (AT) macieira.info - thiago (AT) kde.org
  Senior Product Manager - Nokia, Qt Development Frameworks
      PGP/GPG: 0x6EF45358; fingerprint:
      E067 918B B660 DBD1 105C  966C 33F5 F005 6EF4 5358



      


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