[gnome-flashback] monitor-normal: prefer modes with same flags as preferred mode

[Alberts Muktupāvels <muktupavels src gnome org>]

commit 3121d921dda17f2a3d560e1a793fcfdbc1a199e0
Author: Jonas Ådahl <jadahl gmail com>
Date:   Wed Oct 18 23:22:01 2017 +0800

    monitor-normal: prefer modes with same flags as preferred mode
    
    When generating GfMonitorMode's, prefer CRTC modes that has the same
    set of flags as the preferred mode. This not only is probably a better
    set of configurable modes, but it'll guarantee that the preferred mode
    is added.
    
    This fixes a crash when the preferred mode was not the first mode with
    the same resolution, refresh rate and set of handled modes.
    
    https://bugzilla.gnome.org/show_bug.cgi?id=789153

 backends/gf-monitor-normal.c  |   28 ++++++++++++++++++++--------
 backends/gf-monitor-private.h |    3 ++-
 backends/gf-monitor-tiled.c   |    4 ++--
 backends/gf-monitor.c         |   15 +++++++++++----
 4 files changed, 35 insertions(+), 15 deletions(-)
---
diff --git a/backends/gf-monitor-normal.c b/backends/gf-monitor-normal.c
index 6377c2d..b2cc170 100644
--- a/backends/gf-monitor-normal.c
+++ b/backends/gf-monitor-normal.c
@@ -36,15 +36,18 @@ generate_modes (GfMonitorNormal *normal)
 {
   GfMonitor *monitor;
   GfOutput *output;
+  GfCrtcModeFlag preferred_mode_flags;
   guint i;
 
   monitor = GF_MONITOR (normal);
   output = gf_monitor_get_main_output (monitor);
+  preferred_mode_flags = output->preferred_mode->flags;
 
   for (i = 0; i < output->n_modes; i++)
     {
       GfCrtcMode *crtc_mode;
       GfMonitorMode *mode;
+      gboolean replace;
 
       crtc_mode = output->modes[i];
 
@@ -60,18 +63,27 @@ generate_modes (GfMonitorNormal *normal)
       mode->crtc_modes[0].output = output;
       mode->crtc_modes[0].crtc_mode = crtc_mode;
 
-      if (gf_monitor_add_mode (monitor, mode))
-        {
-          if (crtc_mode == output->preferred_mode)
-            gf_monitor_set_preferred_mode (monitor, mode);
+      /*
+       * We don't distinguish between all available mode flags, just the ones
+       * that are configurable. We still need to pick some mode though, so
+       * prefer ones that has the same set of flags as the preferred mode;
+       * otherwise take the first one in the list. This guarantees that the
+       * preferred mode is always added.
+       */
+      replace = crtc_mode->flags == preferred_mode_flags;
 
-          if (output->crtc && crtc_mode == output->crtc->current_mode)
-            gf_monitor_set_current_mode (monitor, mode);
-        }
-      else
+      if (!gf_monitor_add_mode (monitor, mode, replace))
         {
+          g_assert (crtc_mode != output->preferred_mode);
           gf_monitor_mode_free (mode);
+          continue;
         }
+
+      if (crtc_mode == output->preferred_mode)
+        gf_monitor_set_preferred_mode (monitor, mode);
+
+      if (output->crtc && crtc_mode == output->crtc->current_mode)
+        gf_monitor_set_current_mode (monitor, mode);
     }
 }
 
diff --git a/backends/gf-monitor-private.h b/backends/gf-monitor-private.h
index 401ffbc..44538db 100644
--- a/backends/gf-monitor-private.h
+++ b/backends/gf-monitor-private.h
@@ -105,7 +105,8 @@ void               gf_monitor_set_preferred_mode         (GfMonitor
 void               gf_monitor_generate_spec              (GfMonitor                  *monitor);
 
 gboolean           gf_monitor_add_mode                   (GfMonitor                  *monitor,
-                                                          GfMonitorMode              *monitor_mode);
+                                                          GfMonitorMode              *monitor_mode,
+                                                          gboolean                    replace);
 
 void               gf_monitor_mode_free                  (GfMonitorMode              *monitor_mode);
 
diff --git a/backends/gf-monitor-tiled.c b/backends/gf-monitor-tiled.c
index ef9d1a3..61334be 100644
--- a/backends/gf-monitor-tiled.c
+++ b/backends/gf-monitor-tiled.c
@@ -268,7 +268,7 @@ generate_tiled_monitor_modes (GfMonitorTiled *tiled)
       mode = l->data;
       tiled_modes = g_list_remove_link (tiled_modes, l);
 
-      if (!gf_monitor_add_mode (monitor, mode))
+      if (!gf_monitor_add_mode (monitor, mode, FALSE))
         {
           gf_monitor_mode_free (mode);
           continue;
@@ -308,7 +308,7 @@ generate_untiled_monitor_modes (GfMonitorTiled *tiled)
       if (!mode)
         continue;
 
-      if (!gf_monitor_add_mode (monitor, mode))
+      if (!gf_monitor_add_mode (monitor, mode, FALSE))
         {
           gf_monitor_mode_free (mode);
           continue;
diff --git a/backends/gf-monitor.c b/backends/gf-monitor.c
index 3426fb4..aef8860 100644
--- a/backends/gf-monitor.c
+++ b/backends/gf-monitor.c
@@ -443,18 +443,25 @@ gf_monitor_generate_spec (GfMonitor *monitor)
 
 gboolean
 gf_monitor_add_mode (GfMonitor     *monitor,
-                     GfMonitorMode *monitor_mode)
+                     GfMonitorMode *monitor_mode,
+                     gboolean       replace)
 {
   GfMonitorPrivate *priv;
+  GfMonitorMode *existing_mode;
 
   priv = gf_monitor_get_instance_private (monitor);
 
-  if (g_hash_table_lookup (priv->mode_ids,
-                           gf_monitor_mode_get_id (monitor_mode)))
+  existing_mode = g_hash_table_lookup (priv->mode_ids,
+                                       gf_monitor_mode_get_id (monitor_mode));
+
+  if (existing_mode && !replace)
     return FALSE;
 
+  if (existing_mode)
+    priv->modes = g_list_remove (priv->modes, existing_mode);
+
   priv->modes = g_list_append (priv->modes, monitor_mode);
-  g_hash_table_insert (priv->mode_ids, monitor_mode->id, monitor_mode);
+  g_hash_table_replace (priv->mode_ids, monitor_mode->id, monitor_mode);
 
   return TRUE;
 }