[gnome-settings-daemon] power: Do not attempt to change the brightness of an output that has been disabled

[Richard Hughes <rhughes src gnome org>]

commit 3c84744716963c40a649330d8dee07fd28ad26f6
Author: Richard Hughes <richard hughsie com>
Date:   Mon Sep 3 11:10:04 2012 +0100

    power: Do not attempt to change the brightness of an output that has been disabled
    
    Resolves: https://bugzilla.gnome.org/show_bug.cgi?id=674434

 plugins/power/gsd-power-manager.c |   20 ++++++++++++++++++++
 1 files changed, 20 insertions(+), 0 deletions(-)
---
diff --git a/plugins/power/gsd-power-manager.c b/plugins/power/gsd-power-manager.c
index 6c00823..64009bb 100644
--- a/plugins/power/gsd-power-manager.c
+++ b/plugins/power/gsd-power-manager.c
@@ -2687,11 +2687,21 @@ backlight_step_up (GsdPowerManager *manager, GError **error)
         gint now;
         gint step;
         guint discrete;
+        GnomeRRCrtc *crtc;
 
         /* prefer xbacklight */
         output = get_primary_output (manager);
         if (output != NULL) {
 
+                crtc = gnome_rr_output_get_crtc (output);
+                if (crtc == NULL) {
+                        g_set_error (error,
+                                     GSD_POWER_MANAGER_ERROR,
+                                     GSD_POWER_MANAGER_ERROR_FAILED,
+                                     "no crtc for %s",
+                                     gnome_rr_output_get_name (output));
+                        goto out;
+                }
                 min = gnome_rr_output_get_backlight_min (output);
                 max = gnome_rr_output_get_backlight_max (output);
                 now = gnome_rr_output_get_backlight (output, error);
@@ -2738,11 +2748,21 @@ backlight_step_down (GsdPowerManager *manager, GError **error)
         gint now;
         gint step;
         guint discrete;
+        GnomeRRCrtc *crtc;
 
         /* prefer xbacklight */
         output = get_primary_output (manager);
         if (output != NULL) {
 
+                crtc = gnome_rr_output_get_crtc (output);
+                if (crtc == NULL) {
+                        g_set_error (error,
+                                     GSD_POWER_MANAGER_ERROR,
+                                     GSD_POWER_MANAGER_ERROR_FAILED,
+                                     "no crtc for %s",
+                                     gnome_rr_output_get_name (output));
+                        goto out;
+                }
                 min = gnome_rr_output_get_backlight_min (output);
                 max = gnome_rr_output_get_backlight_max (output);
                 now = gnome_rr_output_get_backlight (output, error);