master ae8b1b8fd4: Implement `display-monitors-changed-functions' on MS Windows

[Po Lu]

branch: master
commit ae8b1b8fd476b8c6240c1337c0c51763d4879ac9
Author: Po Lu <luangruo@yahoo.com>
Commit: Po Lu <luangruo@yahoo.com>

    Implement `display-monitors-changed-functions' on MS Windows
    
    * src/w32term.c (w32_read_socket): Handle WM_DISPLAYCHANGE by
    sending monitor change events.
---
 src/w32term.c | 23 +++++++++++++++++++++++
 1 file changed, 23 insertions(+)

diff --git a/src/w32term.c b/src/w32term.c
index da7ac37972..373c5b5f78 100644
--- a/src/w32term.c
+++ b/src/w32term.c
@@ -5912,6 +5912,29 @@ w32_read_socket (struct terminal *terminal,
                         (short) HIWORD (msg.msg.lParam)));
            }
 
+         /* According to the MS documentation, this message is sent
+            to each window whenever a monitor is added, removed, or
+            has its resolution change.  Detect duplicate events when
+            there are multiple frames by ensuring only one event is
+            put in the keyboard buffer at any given time.  */
+         {
+           union buffered_input_event *ev;
+
+           ev = (kbd_store_ptr == kbd_buffer
+                 ? kbd_buffer + KBD_BUFFER_SIZE - 1
+                 : kbd_store_ptr - 1);
+
+           if (kbd_store_ptr != kbd_fetch_ptr
+               && ev->ie.kind == MONITORS_CHANGED_EVENT
+               && XTERMINAL (ev->ie.arg) == dpyinfo->terminal)
+             /* Don't store a MONITORS_CHANGED_EVENT if there is
+                already an undelivered event on the queue.  */
+             break;
+
+           inev.kind = MONITORS_CHANGED_EVENT;
+           XSETTERMINAL (inev.arg, dpyinfo->terminal);
+         }
+
          check_visibility = 1;
          break;