[gnome-flashback] display-config: add a few helpers to clear structs

[Alberts Muktupāvels <muktupavels src gnome org>]

commit 2130831794b079ad1e399ed950fe092eb9bb0b15
Author: Alberts Muktupāvels <alberts muktupavels gmail com>
Date:   Sun Nov 29 21:23:20 2015 +0200

    display-config: add a few helpers to clear structs
    
    These are useful for child classes to unwind cleanly when constructing
    their structures.
    
    Based on mutter commit:
    https://git.gnome.org/browse/mutter/commit/?id=bff75b64be3da88385173520c4f517693f02971c
    
    https://bugzilla.gnome.org/show_bug.cgi?id=756796

 .../libdisplay-config/flashback-monitor-manager.c  |   72 ++++++++++++++------
 1 files changed, 52 insertions(+), 20 deletions(-)
---
diff --git a/gnome-flashback/libdisplay-config/flashback-monitor-manager.c 
b/gnome-flashback/libdisplay-config/flashback-monitor-manager.c
index abdf346..f8155d6 100644
--- a/gnome-flashback/libdisplay-config/flashback-monitor-manager.c
+++ b/gnome-flashback/libdisplay-config/flashback-monitor-manager.c
@@ -1044,45 +1044,75 @@ make_logical_config (FlashbackMonitorManager *manager)
 }
 
 static void
+clear_output (MetaOutput *output)
+{
+  g_free (output->name);
+  g_free (output->vendor);
+  g_free (output->product);
+  g_free (output->serial);
+  g_free (output->modes);
+  g_free (output->possible_crtcs);
+  g_free (output->possible_clones);
+
+  if (output->driver_notify)
+    output->driver_notify (output);
+
+  memset (output, 0, sizeof (*output));
+}
+
+static void
 free_output_array (MetaOutput *old_outputs,
                    int         n_old_outputs)
 {
   int i;
 
   for (i = 0; i < n_old_outputs; i++)
-    {
-      g_free (old_outputs[i].name);
-      g_free (old_outputs[i].vendor);
-      g_free (old_outputs[i].product);
-      g_free (old_outputs[i].serial);
-      g_free (old_outputs[i].modes);
-      g_free (old_outputs[i].possible_crtcs);
-      g_free (old_outputs[i].possible_clones);
-
-      if (old_outputs[i].driver_notify)
-        old_outputs[i].driver_notify (&old_outputs[i]);
-    }
+    clear_output (&old_outputs[i]);
 
   g_free (old_outputs);
 }
 
 static void
+clear_mode (MetaMonitorMode *mode)
+{
+  g_free (mode->name);
+
+  if (mode->driver_notify)
+    mode->driver_notify (mode);
+
+  memset (mode, 0, sizeof (*mode));
+}
+
+static void
 free_mode_array (MetaMonitorMode *old_modes,
                  int              n_old_modes)
 {
   int i;
 
   for (i = 0; i < n_old_modes; i++)
-    {
-      g_free (old_modes[i].name);
-
-      if (old_modes[i].driver_notify)
-        old_modes[i].driver_notify (&old_modes[i]);
-    }
+    clear_mode (&old_modes[i]);
 
   g_free (old_modes);
 }
 
+static void
+clear_crtc (MetaCRTC *crtc)
+{
+  memset (crtc, 0, sizeof (*crtc));
+}
+
+static void
+free_crtc_array (MetaCRTC *old_crtcs,
+                 int       n_old_crtcs)
+{
+  int i;
+
+  for (i = 0; i < n_old_crtcs; i++)
+    clear_crtc (&old_crtcs[i]);
+
+  g_free (old_crtcs);
+}
+
 static guint8 *
 get_edid_property (Display  *dpy,
                    RROutput  output,
@@ -1482,8 +1512,8 @@ flashback_monitor_manager_finalize (GObject *object)
 
   free_output_array (manager->outputs, manager->n_outputs);
   free_mode_array (manager->modes, manager->n_modes);
+  free_crtc_array (manager->crtcs, manager->n_crtcs);
   g_free (manager->monitor_infos);
-  g_free (manager->crtcs);
 
   G_OBJECT_CLASS (flashback_monitor_manager_parent_class)->finalize (object);
 }
@@ -1954,6 +1984,7 @@ flashback_monitor_manager_read_current_config (FlashbackMonitorManager *manager)
   MetaCRTC *old_crtcs;
   MetaMonitorMode *old_modes;
   unsigned int n_old_outputs;
+  unsigned int n_old_crtcs;
   unsigned int n_old_modes;
 
   /* Some implementations of read_current use the existing information
@@ -1964,6 +1995,7 @@ flashback_monitor_manager_read_current_config (FlashbackMonitorManager *manager)
   old_modes = manager->modes;
   n_old_modes = manager->n_modes;
   old_crtcs = manager->crtcs;
+  n_old_crtcs = manager->n_crtcs;
 
   manager->serial++;
 
@@ -1971,7 +2003,7 @@ flashback_monitor_manager_read_current_config (FlashbackMonitorManager *manager)
 
   free_output_array (old_outputs, n_old_outputs);
   free_mode_array (old_modes, n_old_modes);
-  g_free (old_crtcs);
+  free_crtc_array (old_crtcs, n_old_crtcs);
 }
 
 void