backends: Compare gpu/crtc/output configurations before applying

This spares us from visible flickering whenever an unchanged configuration
is reapplied, eg. after lid open. The code in the X11 paths that did the
same comparisons has been removed in favor of the generic checks.

https://bugzilla.gnome.org/show_bug.cgi?id=791879

src/backends/meta-monitor-manager-private.h

@@ -388,4 +388,10 @@ gboolean meta_monitor_has_aspect_as_size (MetaMonitor *monitor);
 char * meta_monitor_manager_get_vendor_name (MetaMonitorManager *manager,
                                              const char         *vendor);
 
+gboolean meta_monitor_manager_get_has_changed (MetaMonitorManager  *manager,
+                                               MetaCrtcInfo       **crtc_infos,
+                                               unsigned int         n_crtc_infos,
+                                               MetaOutputInfo     **output_infos,
+                                               unsigned int         n_output_infos);
+
 #endif /* META_MONITOR_MANAGER_PRIVATE_H */

src/backends/meta-monitor-manager.c

@@ -483,6 +483,158 @@ meta_monitor_manager_ensure_initial_config (MetaMonitorManager *manager)
   META_MONITOR_MANAGER_GET_CLASS (manager)->ensure_initial_config (manager);
 }
 
+static gboolean
+is_crtc_assignment_changed (MetaCrtc      *crtc,
+                            MetaCrtcInfo **crtc_infos,
+                            unsigned int   n_crtc_infos)
+{
+  unsigned int i;
+
+  for (i = 0; i < n_crtc_infos; i++)
+    {
+      MetaCrtcInfo *crtc_info = crtc_infos[i];
+      unsigned int j;
+
+      if (crtc_info->crtc != crtc)
+        continue;
+
+      if (crtc->current_mode != crtc_info->mode)
+        return TRUE;
+
+      if (crtc->rect.x != crtc_info->x)
+        return TRUE;
+
+      if (crtc->rect.y != crtc_info->y)
+        return TRUE;
+
+      if (crtc->transform != crtc_info->transform)
+        return TRUE;
+
+      for (j = 0; j < crtc_info->outputs->len; j++)
+        {
+          MetaOutput *output = ((MetaOutput**) crtc_info->outputs->pdata)[j];
+          MetaCrtc *assigned_crtc;
+
+          assigned_crtc = meta_output_get_assigned_crtc (output);
+          if (assigned_crtc != crtc)
+            return TRUE;
+        }
+
+      return FALSE;
+    }
+
+  return crtc->current_mode != NULL;
+}
+
+static gboolean
+is_output_assignment_changed (MetaOutput      *output,
+                              MetaCrtcInfo   **crtc_infos,
+                              unsigned int     n_crtc_infos,
+                              MetaOutputInfo **output_infos,
+                              unsigned int     n_output_infos)
+{
+  MetaCrtc *assigned_crtc;
+  gboolean output_is_found = FALSE;
+  unsigned int i;
+
+  for (i = 0; i < n_output_infos; i++)
+    {
+      MetaOutputInfo *output_info = output_infos[i];
+
+      if (output_info->output != output)
+        continue;
+
+      if (output->is_primary != output_info->is_primary)
+        return TRUE;
+
+      if (output->is_presentation != output_info->is_presentation)
+        return TRUE;
+
+      if (output->is_underscanning != output_info->is_underscanning)
+        return TRUE;
+
+      output_is_found = TRUE;
+    }
+
+  assigned_crtc = meta_output_get_assigned_crtc (output);
+
+  if (!output_is_found)
+    return assigned_crtc != NULL;
+
+  for (i = 0; i < n_crtc_infos; i++)
+    {
+      MetaCrtcInfo *crtc_info = crtc_infos[i];
+      unsigned int j;
+
+      for (j = 0; j < crtc_info->outputs->len; j++)
+        {
+          MetaOutput *crtc_info_output =
+            ((MetaOutput**) crtc_info->outputs->pdata)[j];
+
+          if (crtc_info_output == output &&
+              crtc_info->crtc == assigned_crtc)
+            return FALSE;
+        }
+    }
+
+  return TRUE;
+}
+
+static gboolean
+is_assignments_changed (MetaMonitorManager *manager,
+                        MetaGpu            *gpu,
+                        MetaCrtcInfo      **crtc_infos,
+                        unsigned int        n_crtc_infos,
+                        MetaOutputInfo    **output_infos,
+                        unsigned int        n_output_infos)
+{
+  GList *l;
+
+  for (l = meta_gpu_get_crtcs (gpu); l; l = l->next)
+    {
+      MetaCrtc *crtc = l->data;
+
+      if (is_crtc_assignment_changed (crtc, crtc_infos, n_crtc_infos))
+        return TRUE;
+    }
+
+  for (l = meta_gpu_get_outputs (gpu); l; l = l->next)
+    {
+      MetaOutput *output = l->data;
+
+      if (is_output_assignment_changed (output,
+                                        crtc_infos,
+                                        n_crtc_infos,
+                                        output_infos,
+                                        n_output_infos))
+        return TRUE;
+    }
+
+  return FALSE;
+}
+
+gboolean
+meta_monitor_manager_get_has_changed (MetaMonitorManager  *manager,
+                                      MetaCrtcInfo       **crtc_infos,
+                                      unsigned int         n_crtc_infos,
+                                      MetaOutputInfo     **output_infos,
+                                      unsigned int         n_output_infos)
+{
+  GList *gpus;
+  GList *l;
+
+  gpus = meta_backend_get_gpus (manager->backend);
+  for (l = gpus; l; l = l->next)
+    {
+      if (is_assignments_changed (manager, l->data,
+                                  crtc_infos, n_crtc_infos,
+                                  output_infos, n_output_infos))
+        return TRUE;
+    }
+
+  return FALSE;
+}
+
 static gboolean
 meta_monitor_manager_apply_monitors_config (MetaMonitorManager      *manager,
                                             MetaMonitorsConfig      *config,

src/backends/native/meta-monitor-manager-kms.c

@@ -77,6 +77,8 @@ struct _MetaMonitorManagerKms
 
   guint hotplug_handler_id;
   guint removed_handler_id;
+
+  guint logical_monitors_invalid : 1;
 };
 
 struct _MetaMonitorManagerKmsClass
@@ -322,6 +324,7 @@ meta_monitor_manager_kms_apply_monitors_config (MetaMonitorManager      *manager
                                                 MetaMonitorsConfigMethod method,
                                                 GError                 **error)
 {
+  MetaMonitorManagerKms *manager_kms = META_MONITOR_MANAGER_KMS (manager);
   GPtrArray *crtc_infos;
   GPtrArray *output_infos;
 
@@ -345,6 +348,26 @@ meta_monitor_manager_kms_apply_monitors_config (MetaMonitorManager      *manager
       return TRUE;
     }
 
+  if (!meta_monitor_manager_get_has_changed (manager,
+                                             (MetaCrtcInfo **) crtc_infos->pdata,
+                                             crtc_infos->len,
+                                             (MetaOutputInfo **) output_infos->pdata,
+                                             output_infos->len))
+    {
+      /* Rebuild logical monitors if invalid, i.e. after
+       * meta_monitor_manager_read_current_state().
+       */
+      if (manager_kms->logical_monitors_invalid)
+        {
+          meta_monitor_manager_rebuild (manager, config);
+          manager_kms->logical_monitors_invalid = FALSE;
+        }
+
+      g_ptr_array_free (crtc_infos, TRUE);
+      g_ptr_array_free (output_infos, TRUE);
+      return TRUE;
+    }
+
   apply_crtc_assignments (manager,
                           (MetaCrtcInfo **) crtc_infos->pdata,
                           crtc_infos->len,
@@ -356,6 +379,7 @@ meta_monitor_manager_kms_apply_monitors_config (MetaMonitorManager      *manager
 
   update_screen_size (manager, config);
   meta_monitor_manager_rebuild (manager, config);
+  manager_kms->logical_monitors_invalid = FALSE;
 
   return TRUE;
 }
@@ -474,6 +498,13 @@ meta_monitor_manager_kms_set_crtc_gamma (MetaMonitorManager *manager,
 static void
 handle_hotplug_event (MetaMonitorManager *manager)
 {
+  MetaMonitorManagerKms *manager_kms = META_MONITOR_MANAGER_KMS (manager);
+
+  /* read_current_state() will rebuild monitors, leaving MetaLogicalMonitors
+   * with stale pointers to those. We will need to rebuild those even though
+   * the configuration might not have actually changed (eg. tty switch).
+   */
+  manager_kms->logical_monitors_invalid = TRUE;
   meta_monitor_manager_read_current_state (manager);
   meta_monitor_manager_on_hotplug (manager);
 }

src/backends/x11/meta-monitor-manager-xrandr.c

@@ -240,103 +240,6 @@ xrandr_set_crtc_config (MetaMonitorManagerXrandr *manager_xrandr,
   return TRUE;
 }
 
-static gboolean
-is_crtc_assignment_changed (MetaCrtc      *crtc,
-                            MetaCrtcInfo **crtc_infos,
-                            unsigned int   n_crtc_infos)
-{
-  unsigned int i;
-
-  for (i = 0; i < n_crtc_infos; i++)
-    {
-      MetaCrtcInfo *crtc_info = crtc_infos[i];
-      unsigned int j;
-
-      if (crtc_info->crtc != crtc)
-        continue;
-
-      if (crtc->current_mode != crtc_info->mode)
-        return TRUE;
-
-      if (crtc->rect.x != crtc_info->x)
-        return TRUE;
-
-      if (crtc->rect.y != crtc_info->y)
-        return TRUE;
-
-      if (crtc->transform != crtc_info->transform)
-        return TRUE;
-
-      for (j = 0; j < crtc_info->outputs->len; j++)
-        {
-          MetaOutput *output = ((MetaOutput**) crtc_info->outputs->pdata)[j];
-          MetaCrtc *assigned_crtc;
-
-          assigned_crtc = meta_output_get_assigned_crtc (output);
-          if (assigned_crtc != crtc)
-            return TRUE;
-        }
-
-      return FALSE;
-    }
-
-  return crtc->current_mode != NULL;
-}
-
-static gboolean
-is_output_assignment_changed (MetaOutput      *output,
-                              MetaCrtcInfo   **crtc_infos,
-                              unsigned int     n_crtc_infos,
-                              MetaOutputInfo **output_infos,
-                              unsigned int     n_output_infos)
-{
-  MetaCrtc *assigned_crtc;
-  gboolean output_is_found = FALSE;
-  unsigned int i;
-
-  for (i = 0; i < n_output_infos; i++)
-    {
-      MetaOutputInfo *output_info = output_infos[i];
-
-      if (output_info->output != output)
-        continue;
-
-      if (output->is_primary != output_info->is_primary)
-        return TRUE;
-
-      if (output->is_presentation != output_info->is_presentation)
-        return TRUE;
-
-      if (output->is_underscanning != output_info->is_underscanning)
-        return TRUE;
-
-      output_is_found = TRUE;
-    }
-
-  assigned_crtc = meta_output_get_assigned_crtc (output);
-
-  if (!output_is_found)
-    return assigned_crtc != NULL;
-
-  for (i = 0; i < n_crtc_infos; i++)
-    {
-      MetaCrtcInfo *crtc_info = crtc_infos[i];
-      unsigned int j;
-
-      for (j = 0; j < crtc_info->outputs->len; j++)
-        {
-          MetaOutput *crtc_info_output =
-            ((MetaOutput**) crtc_info->outputs->pdata)[j];
-
-          if (crtc_info_output == output &&
-              crtc_info->crtc == assigned_crtc)
-            return FALSE;
-        }
-    }
-
-  return TRUE;
-}
-
 static MetaGpu *
 meta_monitor_manager_xrandr_get_gpu (MetaMonitorManagerXrandr *manager_xrandr)
 {
@@ -346,41 +249,6 @@ meta_monitor_manager_xrandr_get_gpu (MetaMonitorManagerXrandr *manager_xrandr)
   return META_GPU (meta_backend_get_gpus (backend)->data);
 }
 
-static gboolean
-is_assignments_changed (MetaMonitorManager *manager,
-                        MetaCrtcInfo      **crtc_infos,
-                        unsigned int        n_crtc_infos,
-                        MetaOutputInfo    **output_infos,
-                        unsigned int        n_output_infos)
-{
-  MetaMonitorManagerXrandr *manager_xrandr =
-    META_MONITOR_MANAGER_XRANDR (manager);
-  MetaGpu *gpu = meta_monitor_manager_xrandr_get_gpu (manager_xrandr);
-  GList *l;
-
-  for (l = meta_gpu_get_crtcs (gpu); l; l = l->next)
-    {
-      MetaCrtc *crtc = l->data;
-
-      if (is_crtc_assignment_changed (crtc, crtc_infos, n_crtc_infos))
-        return TRUE;
-    }
-
-  for (l = meta_gpu_get_outputs (gpu); l; l = l->next)
-    {
-      MetaOutput *output = l->data;
-
-      if (is_output_assignment_changed (output,
-                                        crtc_infos,
-                                        n_crtc_infos,
-                                        output_infos,
-                                        n_output_infos))
-        return TRUE;
-    }
-
-  return FALSE;
-}
-
 static void
 apply_crtc_assignments (MetaMonitorManager *manager,
                         gboolean            save_timestamp,
@@ -651,7 +519,7 @@ meta_monitor_manager_xrandr_apply_monitors_config (MetaMonitorManager      *mana
        * must check that our new assignment actually changes anything, otherwise
        * just update the logical state.
        */
-      if (is_assignments_changed (manager,
+      if (meta_monitor_manager_get_has_changed (manager,
                                                 (MetaCrtcInfo **) crtc_infos->pdata,
                                                 crtc_infos->len,
                                                 (MetaOutputInfo **) output_infos->pdata,