[glib] gsource: allow NULL check and prepare functions

[Ryan Lortie <ryanl src gnome org>]

commit 6d25e349988d4c40b066d548383fce3b126a7a43
Author: Ryan Lortie <desrt desrt ca>
Date:   Mon Oct 29 18:26:05 2012 +0100

    gsource: allow NULL check and prepare functions
    
    Allow for NULL GSourceFuncs.check() and .prepare().
    
    For prepare() the source will be taken not to be ready and having an
    infinite timeout.  For check() the source will be taken not to be ready.
    
    https://bugzilla.gnome.org/show_bug.cgi?id=686853

 glib/gmain.c |   54 ++++++++++++++++++++++++++++++++++--------------------
 glib/gmain.h |    8 ++++++--
 2 files changed, 40 insertions(+), 22 deletions(-)
---
diff --git a/glib/gmain.c b/glib/gmain.c
index 217eaf6..071694c 100644
--- a/glib/gmain.c
+++ b/glib/gmain.c
@@ -3045,17 +3045,26 @@ g_main_context_prepare (GMainContext *context,
       if (!(source->flags & G_SOURCE_READY))
 	{
 	  gboolean result;
-	  gboolean (*prepare)  (GSource  *source, 
-				gint     *timeout);
+	  gboolean (* prepare) (GSource  *source,
+                                gint     *timeout);
 
-	  prepare = source->source_funcs->prepare;
-	  context->in_check_or_prepare++;
-	  UNLOCK_CONTEXT (context);
+          prepare = source->source_funcs->prepare;
 
-	  result = (*prepare) (source, &source_timeout);
+          if (prepare)
+            {
+              context->in_check_or_prepare++;
+              UNLOCK_CONTEXT (context);
 
-	  LOCK_CONTEXT (context);
-	  context->in_check_or_prepare--;
+              result = (* prepare) (source, &source_timeout);
+
+              LOCK_CONTEXT (context);
+              context->in_check_or_prepare--;
+            }
+          else
+            {
+              source_timeout = -1;
+              result = FALSE;
+            }
 
 	  if (result)
 	    {
@@ -3227,19 +3236,24 @@ g_main_context_check (GMainContext *context,
 
       if (!(source->flags & G_SOURCE_READY))
 	{
-	  gboolean result;
-	  gboolean (*check) (GSource  *source);
+          gboolean result;
+          gboolean (* check) (GSource *source);
+
+          check = source->source_funcs->check;
+
+          if (check)
+            {
+              context->in_check_or_prepare++;
+              UNLOCK_CONTEXT (context);
+
+              result = (* check) (source);
+
+              LOCK_CONTEXT (context);
+              context->in_check_or_prepare--;
+            }
+          else
+            result = FALSE;
 
-	  check = source->source_funcs->check;
-	  
-	  context->in_check_or_prepare++;
-	  UNLOCK_CONTEXT (context);
-	  
-	  result = (*check) (source);
-	  
-	  LOCK_CONTEXT (context);
-	  context->in_check_or_prepare--;
-	  
 	  if (result)
 	    {
 	      GSource *ready_source = source;
diff --git a/glib/gmain.h b/glib/gmain.h
index 5a6a72a..04cf2f8 100644
--- a/glib/gmain.h
+++ b/glib/gmain.h
@@ -86,11 +86,15 @@ typedef struct _GSourceCallbackFuncs    GSourceCallbackFuncs;
  *     a @timeout_ value which should be the maximum timeout (in milliseconds)
  *     which should be passed to the poll() call. The actual timeout used will
  *     be -1 if all sources returned -1, or it will be the minimum of all the
- *     @timeout_ values returned which were >= 0.
+ *     @timeout_ values returned which were >= 0.  Since 2.36 this may
+ *     be %NULL, in which case the effect is as if the function always
+ *     returns %FALSE with a timeout of -1.
  * @check: Called after all the file descriptors are polled. The source
  *     should return %TRUE if it is ready to be dispatched. Note that some
  *     time may have passed since the previous prepare function was called,
- *     so the source should be checked again here.
+ *     so the source should be checked again here.  Since 2.36 this may
+ *     be %NULL, in which case the effect is as if the function always
+ *     returns %FALSE.
  * @dispatch: Called to dispatch the event source, after it has returned
  *     %TRUE in either its @prepare or its @check function. The @dispatch
  *     function is passed in a callback function and data. The callback