From d2cc8089a6fd31e302b23ac787d84ff5a3257b6c Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Florian=20M=C3=BCllner?= <fmuellner@gnome.org>
Date: Thu, 28 Jan 2016 15:26:33 +0100
Subject: [PATCH] monitor-config: Consider external layout before default
 linear config

In case of no existing configuration, we use a default layout of
aligning attached displays horizontally. This sidesteps any layout
configuration that is done externally, for instance via xorg.conf,
which is not desirable. Instead, base the initial configuration on
the existing layout if it passes some sanity checks before falling
back to the default linear config.
---
 src/backends/meta-monitor-config.c | 76 +++++++++++++++++++++++++++++---------
 1 file changed, 59 insertions(+), 17 deletions(-)

diff --git a/src/backends/meta-monitor-config.c b/src/backends/meta-monitor-config.c
index 21e3126f2..492b0ffe1 100644
--- a/src/backends/meta-monitor-config.c
+++ b/src/backends/meta-monitor-config.c
@@ -1130,6 +1130,23 @@ init_config_from_preferred_mode (MetaOutputConfig *config,
   config->is_presentation = FALSE;
 }
 
+static void
+init_config_from_output (MetaOutputConfig *config,
+                         MetaOutput       *output)
+{
+  config->enabled = (output->crtc != NULL);
+
+  if (!config->enabled)
+    return;
+
+  config->rect = output->crtc->rect;
+  config->refresh_rate = output->crtc->current_mode->refresh_rate;
+  config->transform = output->crtc->transform;
+  config->is_primary = output->is_primary;
+  config->is_presentation = output->is_presentation;
+  config->is_underscanning = output->is_underscanning;
+}
+
 /* This function handles configuring the outputs when the driver provides a
  * suggested layout position for each output. This is done in recent versions
  * of qxl and allows displays to be aligned on the guest in the same order as
@@ -1368,6 +1385,45 @@ extend_stored_config (MetaMonitorConfig *self,
   return FALSE;
 }
 
+static gboolean
+make_initial_config_from_current (MetaMonitorConfig *self,
+                                  MetaOutput        *outputs,
+                                  unsigned           n_outputs,
+                                  int                max_width,
+                                  int                max_height,
+                                  MetaConfiguration *config)
+{
+  GList *region = NULL;
+  unsigned i;
+
+  g_return_val_if_fail (config != NULL, FALSE);
+
+  if (g_hash_table_size (self->configs) > 0)
+    return FALSE;
+
+  g_assert (config->n_outputs == n_outputs);
+
+  for (i = 0; i < n_outputs; i++)
+    {
+      init_config_from_output (&config->outputs[i], &outputs[i]);
+
+      /* Reject the configuration if the suggested positions result in
+       * overlapping displays */
+      if (meta_rectangle_overlaps_with_region (region, &config->outputs[i].rect))
+        {
+          g_warning ("Overlapping outputs, rejecting suggested configuration");
+          g_list_free (region);
+          return FALSE;
+        }
+
+      region = g_list_prepend (region, &config->outputs[i].rect);
+    }
+
+  g_list_free (region);
+
+  return TRUE;
+}
+
 static MetaConfiguration *
 make_default_config (MetaMonitorConfig *self,
                      MetaOutput        *outputs,
@@ -1399,6 +1455,9 @@ make_default_config (MetaMonitorConfig *self,
       extend_stored_config (self, outputs, n_outputs, max_width, max_height, ret))
       goto check_limits;
 
+  if (make_initial_config_from_current (self, outputs, n_outputs, max_width, max_height, ret))
+      goto check_limits;
+
   make_linear_config (self, outputs, n_outputs, max_width, max_height, ret);
 
 check_limits:
@@ -1500,23 +1559,6 @@ meta_monitor_config_make_default (MetaMonitorConfig  *self,
     }
 }
 
-static void
-init_config_from_output (MetaOutputConfig *config,
-                         MetaOutput       *output)
-{
-  config->enabled = (output->crtc != NULL);
-
-  if (!config->enabled)
-    return;
-
-  config->rect = output->crtc->rect;
-  config->refresh_rate = output->crtc->current_mode->refresh_rate;
-  config->transform = output->crtc->transform;
-  config->is_primary = output->is_primary;
-  config->is_presentation = output->is_presentation;
-  config->is_underscanning = output->is_underscanning;
-}
-
 void
 meta_monitor_config_update_current (MetaMonitorConfig  *self,
                                     MetaMonitorManager *manager)
-- 
2.12.0