From 1b1b3456bc88a71b932b102d725c5ad29ed408d0 Mon Sep 17 00:00:00 2001
From: Uli Schlachter <psychon@znc.in>
Date: Wed, 3 Oct 2018 14:20:33 +0200
Subject: [PATCH] Convert XGetSelectionOwner to XCB

This also fixes a memory leak: buf was not freed if another composite
manager was already running.

Signed-off-by: Uli Schlachter <psychon@znc.in>
---
 src/compton.c | 10 ++++++++--
 1 file changed, 8 insertions(+), 2 deletions(-)

diff --git a/src/compton.c b/src/compton.c
index c6a8aed..9f131a3 100644
--- a/src/compton.c
+++ b/src/compton.c
@@ -3562,13 +3562,19 @@ register_cm(session_t *ps) {
     snprintf(buf, len, REGISTER_PROP "%d", ps->scr);
     buf[len - 1] = '\0';
     atom = get_atom(ps, buf);
+    free(buf);
 
-    if (XGetSelectionOwner(ps->dpy, atom) != None) {
+    xcb_get_selection_owner_reply_t *reply =
+      xcb_get_selection_owner_reply(c,
+          xcb_get_selection_owner(c, atom), NULL);
+
+    if (reply && reply->owner != XCB_NONE) {
+      free(reply);
       fprintf(stderr, "Another composite manager is already running\n");
       return false;
     }
+    free(reply);
     xcb_set_selection_owner(c, ps->reg_win, atom, 0);
-    free(buf);
   }
 
   return true;