Potential need for librsvg API breakage

["Dominic Lachowicz" <domlachowicz gmail com>]

Hi,

So I'm currently faced with a dilemma that's hitting a lot of users,
causing their applications to crash and otherwise behave badly. I'd
appreciate if people might offer any insight they had on the issue.

In the 2.16.x series, librsvg's fundamental "type", the RsvgHandle,
became a subclass of GObject, and is registered via
g_type_register_static(). AFAIK, this relationship isn't exposed in
any way that the public ABI is concerned (i.e. RsvgHandle is just a
anonymous typedef in the header file).

The problem is that librsvg is a library that gets used by a lot of
plugins - I can think of at least 3 places: AbiWord's image loader,
GdkPixbuf's "loader" architecture, and GTK+'s theme engine. Some of
these (GTK+'s theme engine bits come to mind) make heavy use of what
GObject calls "dynamic types" that get loaded/unloaded as necessary,
and the GModule that ultimately called
g_type_register_static(RSVG_TYPE_HANDLE, ...) may get unloaded. Since
there is no way to signal that types need to be unregistered, this
causes subsequent registration of the RsvgHandle type to fail, and
lots of code to go belly-up. This is bad.

Now, I don't intend to pass judgment on the type registration system.
I just want to come up with the best way to fix the problem I'm
encountering. I can think of a few solutions, but I welcome other
ideas and suggestions for implementing my proposals.

1) Make helper-processes that do the heavy lifting. Have the plugins
call those processes via a wire protocol (see also: The Gimp). The
helper-process calls type registration. Problem goes away.
Pros: No API breakage
Cons: A decent amount of work. Performance penalties in at least 2
places (pixbuf loading, theme engine) where performance actually
matters.

2) Break API. Involves changing documentation, removing type
registration, etc. Probably need to tweak libtool bits to suggest
interface breakage.
Pros: No performance hit
Cons: The obvious. Plus, Rsvg makes use of other GObject-based
libraries (libgsf, gnome-vfs) that may still in-turn exhibit problems.

3) Whatever you all come up with

Thanks for your help and understanding,
Dom
--
"I believe in making the world safe for our children, but not our
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