[Qt-interest] About Plugin Architecture in QT

[Andreas Pakulat]

On 30.04.09 19:46:31, hakiim warrick wrote:
> 
> Hi, thanks a lot, the point i couldnt get is, doesnt it hurt the backward compatibility of the software?
> It comes weird to me that plugins should be built with exactly the same version of Qt that the application is built. Say, we built the main app with Qt 4.5 and released it, what if a 3rd party wants to add a plugin, say a video processing filter, to the app after 1 year? Should he build the plugin with the old 4.5 version?

Well, if the plugin restricts itself to Qt4.5 API and makes sure it
links against the same C runtime as the hosting application on the
platforms where this is needed then its ok to build it against Qt4.6.
The problem is if you're not taking care of that, you might hit a crash
far later in the application, which seems totally unrelated to anything.
Its not like in java where a plugin compiled for 1.6 simply doesn't load
with java 1.5.

> And by the way, do you mean that plugins are executables(in win32 for ex.)? Cant they be added as dlls ?

Usually plugins are dll's, but nothing keeps you from developing a good
IPC framework and using standalone executables as plugins. That approach
would also free you from any linking issues as pointed out above. All
you'd have to make sure is that both the plugin and the hosting
application agree on the available plugin framework API via some version
number.

Andreas

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