From 78b41e542ba484da0df5c886eddfc25d087034ae Mon Sep 17 00:00:00 2001
From: Giovanni Campagna <gcampagn@redhat.com>
Date: Fri, 16 Aug 2013 19:02:57 +0200
Subject: [PATCH] MonitorXrandr: follow the right order in applying the new
 configuration

First disable CRTCs that should be off in the new configuration,
then resize the framebuffer, then enable the new CRTCs.
If we don't do that, and we're making the screen smaller, X complains
with a BadMatch.

https://bugzilla.gnome.org/show_bug.cgi?id=705670
---
 src/core/monitor-xrandr.c | 94 +++++++++++++++++++++++----------------
 1 file changed, 56 insertions(+), 38 deletions(-)

diff --git a/src/core/monitor-xrandr.c b/src/core/monitor-xrandr.c
index 2a04993e4..af51e8621 100644
--- a/src/core/monitor-xrandr.c
+++ b/src/core/monitor-xrandr.c
@@ -660,10 +660,13 @@ meta_monitor_manager_xrandr_apply_configuration (MetaMonitorManager *manager,
 
   meta_display_grab (meta_get_display ());
 
+  /* First compute the new size of the screen (framebuffer) */
   width = 0; height = 0;
   for (i = 0; i < n_crtcs; i++)
     {
       MetaCRTCInfo *crtc_info = crtcs[i];
+      MetaCRTC *crtc = crtc_info->crtc;
+      crtc->dirty = TRUE;
 
       if (crtc_info->mode == NULL)
         continue;
@@ -680,25 +683,19 @@ meta_monitor_manager_xrandr_apply_configuration (MetaMonitorManager *manager,
         }
     }
 
-  g_assert (width > 0 && height > 0);
-  /* The 'physical size' of an X screen is meaningless if that screen
-   * can consist of many monitors. So just pick a size that make the
-   * dpi 96.
-   *
-   * Firefox and Evince apparently believe what X tells them.
-   */
-  width_mm = (width / DPI_FALLBACK) * 25.4 + 0.5;
-  height_mm = (height / DPI_FALLBACK) * 25.4 + 0.5;
-  XRRSetScreenSize (manager_xrandr->xdisplay, DefaultRootWindow (manager_xrandr->xdisplay),
-                    width, height, width_mm, height_mm);
-
+  /* Second disable all newly disabled CRTCs, or CRTCs that in the previous
+     configuration would be outside the new framebuffer (otherwise X complains
+     loudly when resizing)
+     CRTC will be enabled again after resizing the FB
+  */
   for (i = 0; i < n_crtcs; i++)
     {
       MetaCRTCInfo *crtc_info = crtcs[i];
       MetaCRTC *crtc = crtc_info->crtc;
-      crtc->dirty = TRUE;
 
-      if (crtc_info->mode == NULL)
+      if (crtc_info->mode == NULL ||
+          crtc->rect.x + crtc->rect.width > width ||
+          crtc->rect.y + crtc->rect.height > height)
         {
           XRRSetCrtcConfig (manager_xrandr->xdisplay,
                             manager_xrandr->resources,
@@ -709,7 +706,51 @@ meta_monitor_manager_xrandr_apply_configuration (MetaMonitorManager *manager,
                             RR_Rotate_0,
                             NULL, 0);
         }
-      else
+    }
+
+  /* Disable CRTCs not mentioned in the list */
+  for (i = 0; i < manager->n_crtcs; i++)
+    {
+      MetaCRTC *crtc = &manager->crtcs[i];
+
+      if (crtc->dirty)
+        {
+          crtc->dirty = FALSE;
+          continue;
+        }
+      if (crtc->current_mode == NULL)
+        continue;
+
+      XRRSetCrtcConfig (manager_xrandr->xdisplay,
+                        manager_xrandr->resources,
+                        (XID)crtc->crtc_id,
+                        manager_xrandr->time,
+                        0, 0,
+                        None,
+                        RR_Rotate_0,
+                        NULL, 0);
+    }
+
+  g_assert (width > 0 && height > 0);
+  /* The 'physical size' of an X screen is meaningless if that screen
+   * can consist of many monitors. So just pick a size that make the
+   * dpi 96.
+   *
+   * Firefox and Evince apparently believe what X tells them.
+   */
+  width_mm = (width / DPI_FALLBACK) * 25.4 + 0.5;
+  height_mm = (height / DPI_FALLBACK) * 25.4 + 0.5;
+  meta_error_trap_push (meta_get_display ());
+  XRRSetScreenSize (manager_xrandr->xdisplay, DefaultRootWindow (manager_xrandr->xdisplay),
+                    width, height, width_mm, height_mm);
+  meta_error_trap_pop (meta_get_display ());
+
+  for (i = 0; i < n_crtcs; i++)
+    {
+      MetaCRTCInfo *crtc_info = crtcs[i];
+      MetaCRTC *crtc = crtc_info->crtc;
+
+      if (crtc_info->mode != NULL)
         {
           MetaMonitorMode *mode;
           XID *outputs;
@@ -761,29 +802,6 @@ meta_monitor_manager_xrandr_apply_configuration (MetaMonitorManager *manager,
                                       output_info->is_presentation);
     }
 
-  /* Disable CRTCs not mentioned in the list */
-  for (i = 0; i < manager->n_crtcs; i++)
-    {
-      MetaCRTC *crtc = &manager->crtcs[i];
-
-      if (crtc->dirty)
-        {
-          crtc->dirty = FALSE;
-          continue;
-        }
-      if (crtc->current_mode == NULL)
-        continue;
-
-      XRRSetCrtcConfig (manager_xrandr->xdisplay,
-                        manager_xrandr->resources,
-                        (XID)crtc->crtc_id,
-                        manager_xrandr->time,
-                        0, 0,
-                        None,
-                        RR_Rotate_0,
-                        NULL, 0);
-    }
-
   meta_display_ungrab (meta_get_display ());
 }