[gimp] libgimp: add gimp_plug_in_info_set_callbacks().

[Jehan <jehanp src gnome org>]

commit febc1a843d23566e86696d9996d166d21a1524c8
Author: Jehan <jehan girinstud io>
Date:   Thu Jul 25 15:17:33 2019 +0200

    libgimp: add gimp_plug_in_info_set_callbacks().
    
    This is an alternative way to set up a plug-in callbacks, apart from
    setting directly the PlugInInfo struct properties.
    The reason is that setting directly the Gimp*Proc properties crashes the
    plug-in, when done through the Python GI binding.
    
    It is most likely a bug in Pygobject, unless we need the proper
    annotation (which I haven't found yet). See:
    https://gitlab.gnome.org/GNOME/pygobject/issues/24#note_564968
    
    Setting these callbacks from the C code works fine though, hence this
    new API. It is to be noted that the '(scope async)' is the most
    important part in this function annotations. Without these annotations,
    the function pointers become invalid at the end of the set_callbacks()
    call, hence the plug-in crashes when they are actually called.
    
    Unfortunally I am also notified by ebassi that using (scope) at all (any
    of the 3 possible values) is just wrong. An API change will be
    necessary. For the time being, I leave this like this, for the sake of
    testing further, but we'll need to improve things.

 libgimp/gimp.c | 24 ++++++++++++++++++++++++
 libgimp/gimp.h |  6 ++++++
 2 files changed, 30 insertions(+)
---
diff --git a/libgimp/gimp.c b/libgimp/gimp.c
index 375f405706..025485db08 100644
--- a/libgimp/gimp.c
+++ b/libgimp/gimp.c
@@ -256,6 +256,30 @@ static GimpPDBStatusType  pdb_error_status   = GIMP_PDB_SUCCESS;
 static gchar             *pdb_error_message  = NULL;
 
 
+/**
+ * gimp_plug_in_info_set_callbacks:
+ * @info: the PLUG_IN_INFO structure
+ * @init_proc:  (closure) (scope async) (nullable): the init procedure
+ * @quit_proc:  (closure) (scope async) (nullable): the quit procedure
+ * @query_proc: (closure) (scope async) (nullable): the query procedure
+ * @run_proc:   (closure) (scope async) (nullable): the run procedure
+ *
+ * The procedure that must be called with the PLUG_IN_INFO structure to
+ * set the initialization, query, run and quit callbacks.
+ **/
+void
+gimp_plug_in_info_set_callbacks (GimpPlugInInfo *info,
+                                 GimpInitProc    init_proc,
+                                 GimpQuitProc    quit_proc,
+                                 GimpQueryProc   query_proc,
+                                 GimpRunProc     run_proc)
+{
+  info->init_proc  = init_proc;
+  info->quit_proc  = quit_proc;
+  info->query_proc = query_proc;
+  info->run_proc   = run_proc;
+}
+
 /**
  * gimp_main:
  * @info: the PLUG_IN_INFO structure
diff --git a/libgimp/gimp.h b/libgimp/gimp.h
index 13df071e67..346c6814d5 100644
--- a/libgimp/gimp.h
+++ b/libgimp/gimp.h
@@ -234,6 +234,12 @@ struct _GimpParam
 #endif
 
 
+void           gimp_plug_in_info_set_callbacks    (GimpPlugInInfo *info,
+                                                   GimpInitProc    init_proc,
+                                                   GimpQuitProc    quit_proc,
+                                                   GimpQueryProc   query_proc,
+                                                   GimpRunProc     run_proc);
+
 /* The main procedure that must be called with the PLUG_IN_INFO structure
  * and the 'argc' and 'argv' that are passed to "main".
  */