gio: deprecate gioscheduler, soft deprecate GSimpleAsyncResult

Reimplement gioscheduler in terms of GTask, and deprecate the original
gioscheduler methods. Update docs to point people to GTask rather than
gioscheduler and GSimpleAsyncResult, but don't actually formally
deprecate GSimpleAsyncResult yet.

https://bugzilla.gnome.org/show_bug.cgi?id=661767

gio/gioscheduler.c

@@ -24,34 +24,30 @@
 
 #include "gioscheduler.h"
 #include "gcancellable.h"
-
+#include "gtask.h"
 
 /**
  * SECTION:gioscheduler
  * @short_description: I/O Scheduler
  * @include: gio/gio.h
  * 
+ * <note><para>
+ *   As of GLib 2.36, the <literal>g_io_scheduler</literal> methods
+ *   are deprecated in favor of #GThreadPool and #GTask.
+ * </para></note>
+ *
  * Schedules asynchronous I/O operations. #GIOScheduler integrates 
  * into the main event loop (#GMainLoop) and uses threads.
- * 
- * <para id="io-priority"><indexterm><primary>I/O priority</primary></indexterm>
- * Each I/O operation has a priority, and the scheduler uses the priorities
- * to determine the order in which operations are executed. They are 
- * <emphasis>not</emphasis> used to determine system-wide I/O scheduling.
- * Priorities are integers, with lower numbers indicating higher priority. 
- * It is recommended to choose priorities between %G_PRIORITY_LOW and 
- * %G_PRIORITY_HIGH, with %G_PRIORITY_DEFAULT as a default.
- * </para>
  **/
 
 struct _GIOSchedulerJob {
   GList *active_link;
+  GTask *task;
+
   GIOSchedulerJobFunc job_func;
-  GSourceFunc cancel_func; /* Runs under job map lock */
   gpointer data;
   GDestroyNotify destroy_notify;
 
-  gint io_priority;
   GCancellable *cancellable;
   gulong cancellable_id;
   GMainContext *context;
@@ -60,98 +56,29 @@ struct _GIOSchedulerJob {
 G_LOCK_DEFINE_STATIC(active_jobs);
 static GList *active_jobs = NULL;
 
-static GThreadPool *job_thread_pool = NULL;
-
-static void io_job_thread (gpointer data,
-			   gpointer user_data);
-
 static void
 g_io_job_free (GIOSchedulerJob *job)
 {
-  if (job->cancellable)
-    {
-      if (job->cancellable_id)
-	g_cancellable_disconnect (job->cancellable, job->cancellable_id);
-      g_object_unref (job->cancellable);
-    }
-  g_main_context_unref (job->context);
-  g_free (job);
-}
-
-static gint
-g_io_job_compare (gconstpointer a,
-		  gconstpointer b,
-		  gpointer      user_data)
-{
-  const GIOSchedulerJob *aa = a;
-  const GIOSchedulerJob *bb = b;
-
-  /* Cancelled jobs are set prio == -1, so that
-     they are executed as quickly as possible */
-  
-  /* Lower value => higher priority */
-  if (aa->io_priority < bb->io_priority)
-    return -1;
-  if (aa->io_priority == bb->io_priority)
-    return 0;
-  return 1;
-}
-
-static gpointer
-init_scheduler (gpointer arg)
-{
-  if (job_thread_pool == NULL)
-    {
-      /* TODO: thread_pool_new can fail */
-      job_thread_pool = g_thread_pool_new (io_job_thread,
-					   NULL,
-					   10,
-					   FALSE,
-					   NULL);
-      if (job_thread_pool != NULL)
-	{
-	  g_thread_pool_set_sort_function (job_thread_pool,
-					   g_io_job_compare,
-					   NULL);
-	}
-    }
-  return NULL;
-}
-
-static void
-on_job_canceled (GCancellable    *cancellable,
-		 gpointer         user_data)
-{
-  GIOSchedulerJob *job = user_data;
-
-  /* This might be called more than once */
-  job->io_priority = -1;
-
-  if (job_thread_pool != NULL)
-    g_thread_pool_set_sort_function (job_thread_pool,
-				     g_io_job_compare,
-				     NULL);
-}
-
-static void
-job_destroy (gpointer data)
-{
-  GIOSchedulerJob *job = data;
-
   if (job->destroy_notify)
     job->destroy_notify (job->data);
 
   G_LOCK (active_jobs);
   active_jobs = g_list_delete_link (active_jobs, job->active_link);
   G_UNLOCK (active_jobs);
-  g_io_job_free (job);
+
+  if (job->cancellable)
+    g_object_unref (job->cancellable);
+  g_main_context_unref (job->context);
+  g_slice_free (GIOSchedulerJob, job);
 }
 
 static void
-io_job_thread (gpointer data,
-	       gpointer user_data)
+io_job_thread (GTask         *task,
+               gpointer       source_object,
+               gpointer       task_data,
+               GCancellable  *cancellable)
 {
-  GIOSchedulerJob *job = data;
+  GIOSchedulerJob *job = task_data;
   gboolean result;
 
   if (job->cancellable)
@@ -165,8 +92,6 @@ io_job_thread (gpointer data,
 
   if (job->cancellable)
     g_cancellable_pop_current (job->cancellable);
-
-  job_destroy (job);
 }
 
 /**
@@ -174,7 +99,7 @@ io_job_thread (gpointer data,
  * @job_func: a #GIOSchedulerJobFunc.
  * @user_data: data to pass to @job_func
  * @notify: (allow-none): a #GDestroyNotify for @user_data, or %NULL
- * @io_priority: the <link linkend="gioscheduler">I/O priority</link> 
+ * @io_priority: the <link linkend="io-priority">I/O priority</link>
  * of the request.
  * @cancellable: optional #GCancellable object, %NULL to ignore.
  *
@@ -186,6 +111,8 @@ io_job_thread (gpointer data,
  * If @cancellable is not %NULL, it can be used to cancel the I/O job
  * by calling g_cancellable_cancel() or by calling 
  * g_io_scheduler_cancel_all_jobs().
+ *
+ * Deprecated: use #GThreadPool or g_task_run_in_thread()
  **/
 void
 g_io_scheduler_push_job (GIOSchedulerJobFunc  job_func,
@@ -194,23 +121,18 @@ g_io_scheduler_push_job (GIOSchedulerJobFunc  job_func,
 			 gint                 io_priority,
 			 GCancellable        *cancellable)
 {
-  static GOnce once_init = G_ONCE_INIT;
   GIOSchedulerJob *job;
+  GTask *task;
 
   g_return_if_fail (job_func != NULL);
 
-  job = g_new0 (GIOSchedulerJob, 1);
+  job = g_slice_new0 (GIOSchedulerJob);
   job->job_func = job_func;
   job->data = user_data;
   job->destroy_notify = notify;
-  job->io_priority = io_priority;
-    
+
   if (cancellable)
-    {
-      job->cancellable = g_object_ref (cancellable);
-      job->cancellable_id = g_cancellable_connect (job->cancellable, (GCallback)on_job_canceled,
-						   job, NULL);
-    }
+    job->cancellable = g_object_ref (cancellable);
 
   job->context = g_main_context_ref_thread_default ();
 
@@ -219,8 +141,11 @@ g_io_scheduler_push_job (GIOSchedulerJobFunc  job_func,
   job->active_link = active_jobs;
   G_UNLOCK (active_jobs);
 
-  g_once (&once_init, init_scheduler, NULL);
-  g_thread_pool_push (job_thread_pool, job, NULL);
+  task = g_task_new (NULL, cancellable, NULL, NULL);
+  g_task_set_task_data (task, job, (GDestroyNotify)g_io_job_free);
+  g_task_set_priority (task, io_priority);
+  g_task_run_in_thread (task, io_job_thread);
+  g_object_unref (task);
 }
 
 /**
@@ -230,6 +155,10 @@ g_io_scheduler_push_job (GIOSchedulerJobFunc  job_func,
  *
  * A job is cancellable if a #GCancellable was passed into
  * g_io_scheduler_push_job().
+ *
+ * Deprecated: You should never call this function, since you don't
+ * know how other libraries in your program might be making use of
+ * gioscheduler.
  **/
 void
 g_io_scheduler_cancel_all_jobs (void)
@@ -305,6 +234,8 @@ mainloop_proxy_free (MainLoopProxy *proxy)
  * blocking the I/O job).
  *
  * Returns: The return value of @func
+ *
+ * Deprecated: Use g_main_context_invoke().
  **/
 gboolean
 g_io_scheduler_job_send_to_mainloop (GIOSchedulerJob *job,
@@ -361,6 +292,8 @@ g_io_scheduler_job_send_to_mainloop (GIOSchedulerJob *job,
  * on to this function you have to ensure that it is not freed before
  * @func is called, either by passing %NULL as @notify to 
  * g_io_scheduler_push_job() or by using refcounting for @user_data.
+ *
+ * Deprecated: Use g_main_context_invoke().
  **/
 void
 g_io_scheduler_job_send_to_mainloop_async (GIOSchedulerJob *job,