From 02baab07033f9db4c1d44e0df8379587ecec2e74 Mon Sep 17 00:00:00 2001
From: Oliver Deja <olideja@web.de>
Date: Mon, 30 Mar 2026 17:37:10 +0000
Subject: [PATCH] x11: displays: Add hotplug event handling

When handling the RRScreenChangeNotify event, auto resize if the
preferred mode was selected and updated.

Fixes: #142
---
 xfsettingsd/displays-x11.c | 51 ++++++++++++++++++++++++++++++++++++++
 1 file changed, 51 insertions(+)

diff --git a/xfsettingsd/displays-x11.c b/xfsettingsd/displays-x11.c
index f96ce6a5..696b17f2 100644
--- a/xfsettingsd/displays-x11.c
+++ b/xfsettingsd/displays-x11.c
@@ -616,6 +616,57 @@ screen_on_event (gpointer data)
         xfconf_channel_set_string (channel, ACTIVE_PROFILE, DEFAULT_SCHEME_NAME);
     }
 
+    /* hotplup event handling: see https://gitlab.xfce.org/xfce/xfce4-settings/-/issues/142 */
+    if (old_outputs->len == helper->outputs->len
+        && helper->resources->timestamp < helper->resources->configTimestamp
+        && edids_changed)
+    {
+        gboolean changed = FALSE;
+
+        for (guint n = 0; n < helper->outputs->len; ++n)
+        {
+            XfceRROutput *output = g_ptr_array_index (helper->outputs, n);
+            XfceRROutput *old_output = g_ptr_array_index (old_outputs, n);
+            XfceRRCrtc *crtc = xfce_displays_helper_x11_find_crtc_by_id (helper, output->info->crtc);
+
+            if (output->id != old_output->id)
+            {
+                xfsettings_dbg (XFSD_DEBUG_DISPLAYS, "Output identifiers or order changed, aborting.");
+                break;
+            }
+
+            if (crtc == NULL)
+                continue;
+
+            /* if the new output has a new preferred mode and the crtc was configured in the previours preferred
+               mode, reconfigure to use the new preferred mode */
+            if (old_output->preferred_mode != output->preferred_mode && old_output->preferred_mode == crtc->mode)
+            {
+                for (gint m = 0; m < helper->resources->nmode; ++m)
+                {
+                    if (output->preferred_mode == helper->resources->modes[m].id)
+                    {
+                        crtc->mode = helper->resources->modes[m].id;
+                        crtc->width = helper->resources->modes[m].width;
+                        crtc->height = helper->resources->modes[m].height;
+                        crtc->changed = TRUE;
+                        xfce_displays_helper_x11_set_outputs (crtc, output);
+
+                        changed |= output->active;
+                        break;
+                    }
+                }
+            }
+        }
+
+        if (changed)
+        {
+            xfce_displays_helper_x11_apply_all (helper);
+            g_ptr_array_unref (old_outputs);
+            return FALSE;
+        }
+    }
+
     if (old_outputs->len > helper->outputs->len || edids_changed)
     {
         gboolean changed = FALSE;
-- 
GitLab