Re: Dynamic library loading with lgi

[Rena <hyperhacker@...>]

On Mon, Nov 19, 2012 at 7:11 AM, Pavel Holejsovsky
<pavel.holejsovsky@gmail.com> wrote:
> On 11/19/12 4:59 AM, Rena wrote:
>>
>> I've run into an issue when porting a program from LuaGnome to lgi.
>> This program loads another C library which uses some GDK functions.
>> Since it's a shared library I guess it expects the host program to
>> load the appropriate GDK libraries as well, and LuaGnome would do
>> this, but lgi does not? So the library can't be loaded:
>>
>> lua5.1: error loading module 'display' from file
>> './display/build/display.so':
>>         ./display/build/display.so: undefined symbol: gdk_draw_rgb_image
>>
>> I feel like I fixed this problem once before, by referencing some GDK
>> function in the Lua script before loading the library that depends on
>> it, so that the GDK libraries would be loaded. But I can't find the
>> program that did that now (maybe I dreamed it?), and the result is
>> even stranger than I expected - lgi.Gdk.draw_rgb_image is nil. As is
>> lgi.Gdk.pixbuf_new, on the off chance that one function had been
>> changed. So I'm not sure how you're meant to even use GDK with lgi,
>> let alone load the library so that others can use it?
>>
>
> This is expected, because gdk_draw_rgb_image() is part of GDK2, but left out
> of GDK3 - all rendering was switched to cairo-only in gtk3.  So assuming
> that you have both GDK2 and GDK3 (together with typelibs) installed, you can
> force using GTK2 (and GDK2 too) explicitly by
>
> local Gtk = lgi.require('Gtk', '2.0')
> local Gdk = lgi.Gdk
>
> Note that once you explicitely ask for Gtk-2.0, it is not needed to repeat
> the version request for Gdk-2.0, because Gdk-2.0 is already loaded as a
> dependency of Gtk-2.0
>
> That said, although writing apps targeted to gtk2 is certainly possible, I'd
> recommend to move to gtk3 if possible at all, because it is actively
> maintained (and this is true for both gtk upstream and lgi gtk overrides).
>
> Note that it is not possible to mix gtk2 and gtk3 in one process, so you
> must really decide whether change/recompile another library for gtk3 or
> target your application to gtk2.
>
> hth,
> Pavel
>
>

Aha, I thought the library wouldn't compile at all in that case, but I
guess it compiles OK because GTK2 is still available, but then fails
to load with GTK3... makes sense. I'll see how to go about porting it.
Thanks for the help.

-- 
Sent from my Game Boy.