Add a hook run upon monitor configuration changes

* doc/lispref/frames.texi (Multiple Terminals): Document new
hook `display-monitors-changed-functions'.
* etc/NEWS: Announce new abnormal hook.

* src/keyboard.c (kbd_buffer_get_event): Handle
MONITORS_CHANGED_EVENT.
(syms_of_keyboard): New hook and defsyms.
* src/termhooks.h (enum event_kind): Add new event
`MONITORS_CHANGED_EVENT'.

* src/xterm.c (handle_one_xevent): Handle RRNotify and
RRScreenChangeNotify events.
(x_term_init): Select for RRScreenChange, RRCrtcChange and
RROutputChange.
* src/xterm.h (struct x_display_info): Improve RandR version
detection.

1 files changed, 23 insertions, 0 deletions

diff --git a/src/keyboard.c b/src/keyboard.c
index 481633f92fe..a2322f1b49d 100644
--- a/src/keyboard.c
+++ b/src/keyboard.c
@@ -4058,6 +4058,18 @@ kbd_buffer_get_event (KBOARD **kbp,
         }
 #endif
 
+      case MONITORS_CHANGED_EVENT:
+        {
+          kbd_fetch_ptr = next_kbd_event (event);
+          input_pending = readable_events (0);
+
+          CALLN (Frun_hook_with_args,
+                 Qdisplay_monitors_changed_functions,
+                 event->ie.arg);
+
+          break;
+        }
+
 #ifdef HAVE_EXT_MENU_BAR
       case MENU_BAR_ACTIVATE_EVENT:
         {
@@ -12609,6 +12621,8 @@ See also `pre-command-hook'.  */);
   DEFSYM (Qtouchscreen_end, "touchscreen-end");
   DEFSYM (Qtouchscreen_update, "touchscreen-update");
   DEFSYM (Qpinch, "pinch");
+  DEFSYM (Qdisplay_monitors_changed_functions,
+          "display-monitors-changed-functions");
 
   DEFSYM (Qcoding, "coding");
 
@@ -12953,6 +12967,15 @@ Otherwise, a wheel event will be sent every time the mouse wheel is
 moved.  */);
   mwheel_coalesce_scroll_events = true;
 
+  DEFVAR_LISP ("display-monitors-changed-functions", Vdisplay_monitors_changed_functions,
+    doc: /* Abnormal hook run when the monitor configuration changes.
+This can happen if a monitor is rotated, moved, plugged in or removed
+from a multi-monitor setup, if the primary monitor changes, or if the
+resolution of a monitor changes.  The hook should accept a single
+argument, which is the terminal on which the monitor configuration
+changed.  */);
+  Vdisplay_monitors_changed_functions = Qnil;
+
   pdumper_do_now_and_after_load (syms_of_keyboard_for_pdumper);
 }