From d4dde314ffbc97cb3431e8803e8fb46ce36c2274 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Daniel=20Ekl=C3=B6f?= <daniel@ekloef.se>
Date: Sun, 28 Dec 2025 13:44:36 +0100
Subject: [PATCH] Use Primary Device Attributes to detect OSC-52 support

Up until recently, there were no reliable way to detect if a terminal
supported OSC-52 or not.
A number or terminal emulators decided to remedy this by including '52'
in their primary DA response.  In short, the presence of 52 in the DA
response means the terminal supports *writing* to the clipboard.
Reading the clipboard is _usually_ supported, but not guaranteed.
It should be noted that Emacs uses both the 'c' and 'p' parameters in
OSC-52, to copy to either PRIMARY, or CLIPBOARD, while the specification
only requires the terminal to implement 'c'.  If a terminal doesn't
support 'p', the OSC-52 request will be silently ignored.
* lisp/term/xterm.el (xterm--init, xterm--primary-da-handler):
Query primary device attributes for OSC-52 support.  (Bug#80083)

Copyright-paperwork-exempt: yes
---
 lisp/term/xterm.el | 30 ++++++++++++++++++++++--------
 1 file changed, 22 insertions(+), 8 deletions(-)

diff --git a/lisp/term/xterm.el b/lisp/term/xterm.el
index f173508d777..3300c2d83cc 100644
--- a/lisp/term/xterm.el
+++ b/lisp/term/xterm.el
@@ -822,6 +822,16 @@ Return the pasted text as a string."
           ;;(xterm--init-activate-get-selection)
           (xterm--init-activate-set-selection))))))
 
+(defun xterm--primary-da-handler ()
+  ;; The reply should be: \e [ ? NUMBER1 ; ... ; NUMBER_N c
+  (let ((str (xterm--read-string ?c)))
+    (when (member "52" (split-string str ";" t))
+      ;; Many modern terminals include 52 in their primary DA response,
+      ;; to indicate support for *writing* to the OS clipboard. The
+      ;; specification does not guarantee the clipboard can be read. See
+      ;; https://github.com/contour-terminal/vt-extensions/blob/master/clipboard-extension.md
+      (xterm--init-activate-set-selection))))
+
 (defvar xterm-query-timeout 2
   "Seconds to wait for an answer from the terminal.
 Can be nil to mean \"no timeout\".")
@@ -948,14 +958,18 @@ We run the first FUNCTION whose STRING matches the input events."
   (tty-set-up-initial-frame-faces)
 
   (if (eq xterm-extra-capabilities 'check)
-      ;; Try to find out the type of terminal by sending a "Secondary
-      ;; Device Attributes (DA)" query.
-      (xterm--query "\e[>0c"
-                    ;; Some terminals (like macOS's Terminal.app) respond to
-                    ;; this query as if it were a "Primary Device Attributes"
-                    ;; query instead, so we should handle that too.
-                    '(("\e[?" . xterm--version-handler)
-                      ("\e[>" . xterm--version-handler)))
+      (progn
+        ;; Try to find out the type of terminal by sending a "Secondary
+        ;; Device Attributes (DA)" query.
+        (xterm--query "\e[>0c"
+                      ;; Some terminals (like macOS's Terminal.app) respond to
+                      ;; this query as if it were a "Primary Device Attributes"
+                      ;; query instead, so we should handle that too.
+                      '(("\e[?" . xterm--version-handler)
+                        ("\e[>" . xterm--version-handler)))
+        ;; Check primary DA for OSC-52 support
+        (xterm--query "\e[c"
+                      '(("\e[?" . xterm--primary-da-handler))))
 
     (when (memq 'reportBackground xterm-extra-capabilities)
       (xterm--query "\e]11;?\e\\"