master c96a6a0c9f: Only preserve PRIMARY and CLIPBOARD selection ownership by default

[Po Lu]

branch: master
commit c96a6a0c9fc44be846834ab1d7d8d527dc8dc5e9
Author: Po Lu <luangruo@yahoo.com>
Commit: Po Lu <luangruo@yahoo.com>

    Only preserve PRIMARY and CLIPBOARD selection ownership by default
    
    * lisp/cus-start.el (standard): Update defcustom type.
    * src/xselect.c (x_should_preserve_selection): New function.
    (x_clear_frame_selections): Use it to determine whether or not
    to preserve a selection.
    * src/xterm.c (x_preserve_selections): Fix tail initialization.
    (syms_of_xterm): Update doc string of
    `x-auto-preserve-selections'.
---
 lisp/cus-start.el |  5 ++++-
 src/xselect.c     | 36 ++++++++++++++++++++++++++++++------
 src/xterm.c       | 10 +++++++---
 3 files changed, 41 insertions(+), 10 deletions(-)

diff --git a/lisp/cus-start.el b/lisp/cus-start.el
index df919fd715..0e1cb4589d 100644
--- a/lisp/cus-start.el
+++ b/lisp/cus-start.el
@@ -834,7 +834,10 @@ since it could result in memory overflow and make Emacs 
crash."
              (x-scroll-event-delta-factor mouse float "29.1")
              (x-gtk-use-native-input keyboard boolean "29.1")
              (x-dnd-disable-motif-drag dnd boolean "29.1")
-             (x-auto-preserve-selections x boolean "29.1")
+             (x-auto-preserve-selections x
+                                         (choice (const :tag "Always preserve 
selections" t)
+                                                 (repeat symbol))
+                                         "29.1")
             ;; xselect.c
             (x-select-enable-clipboard-manager killing boolean "24.1")
             ;; xsettings.c
diff --git a/src/xselect.c b/src/xselect.c
index 1750cfb8bd..d6e6d0c30b 100644
--- a/src/xselect.c
+++ b/src/xselect.c
@@ -1084,6 +1084,26 @@ x_handle_selection_event (struct selection_input_event 
*event)
     x_handle_selection_request (event);
 }
 
+static bool
+x_should_preserve_selection (Lisp_Object selection)
+{
+  Lisp_Object tem;
+
+  tem = Vx_auto_preserve_selections;
+
+  if (CONSP (Vx_auto_preserve_selections))
+    {
+      FOR_EACH_TAIL_SAFE (tem)
+       {
+         if (EQ (XCAR (tem), selection))
+           return true;
+       }
+
+      return false;
+    }
+
+  return !NILP (tem);
+}
 
 /* Clear all selections that were made from frame F.
    We do this when about to delete a frame.  */
@@ -1091,7 +1111,7 @@ x_handle_selection_event (struct selection_input_event 
*event)
 void
 x_clear_frame_selections (struct frame *f)
 {
-  Lisp_Object frame, rest, lost;
+  Lisp_Object frame, rest, lost, selection;
   struct x_display_info *dpyinfo = FRAME_DISPLAY_INFO (f);
   struct terminal *t = dpyinfo->terminal;
 
@@ -1102,10 +1122,12 @@ x_clear_frame_selections (struct frame *f)
   while (CONSP (t->Vselection_alist)
         && EQ (frame, XCAR (XCDR (XCDR (XCDR (XCAR (t->Vselection_alist)))))))
     {
-      if (!x_auto_preserve_selections)
+      selection = Fcar (Fcar (t->Vselection_alist));
+
+      if (!x_should_preserve_selection (selection))
        /* Run the `x-lost-selection-functions' abnormal hook.  */
        CALLN (Frun_hook_with_args, Qx_lost_selection_functions,
-              Fcar (Fcar (t->Vselection_alist)));
+              selection);
       else
        lost = Fcons (Fcar (t->Vselection_alist), lost);
 
@@ -1117,9 +1139,11 @@ x_clear_frame_selections (struct frame *f)
     if (CONSP (XCDR (rest))
        && EQ (frame, XCAR (XCDR (XCDR (XCDR (XCAR (XCDR (rest))))))))
       {
-       if (!x_auto_preserve_selections)
+       selection = XCAR (XCAR (XCDR (rest)));
+
+       if (!x_should_preserve_selection (selection))
          CALLN (Frun_hook_with_args, Qx_lost_selection_functions,
-                XCAR (XCAR (XCDR (rest))));
+                selection);
        else
          lost = Fcons (XCAR (XCDR (rest)), lost);
 
@@ -1127,7 +1151,7 @@ x_clear_frame_selections (struct frame *f)
        break;
       }
 
-  if (x_auto_preserve_selections)
+  if (!NILP (lost))
     x_preserve_selections (dpyinfo, lost, frame);
 }
 
diff --git a/src/xterm.c b/src/xterm.c
index 63b625f383..c0a01d0d73 100644
--- a/src/xterm.c
+++ b/src/xterm.c
@@ -28096,6 +28096,7 @@ x_preserve_selections (struct x_display_info *dpyinfo, 
Lisp_Object lost,
        }
 
       nowners = 0;
+      tail = lost;
 
       FOR_EACH_TAIL_SAFE (tail)
        {
@@ -28458,10 +28459,13 @@ executing the protocol request.  Otherwise, errors 
will be silently
 ignored without waiting, which is generally faster.  */);
   x_fast_protocol_requests = false;
 
-  DEFVAR_BOOL ("x-auto-preserve-selections", x_auto_preserve_selections,
+  DEFVAR_LISP ("x-auto-preserve-selections", Vx_auto_preserve_selections,
     doc: /* Whether or not to transfer selection ownership when deleting a 
frame.
 When non-nil, deleting a frame that is currently the owner of a
 selection will cause its ownership to be transferred to another frame
-on the same display.  */);
-  x_auto_preserve_selections = true;
+on the same display.
+
+In addition, when this variable is a list, only preserve the
+selections whose names are contained within.  */);
+  Vx_auto_preserve_selections = list2 (QCLIPBOARD, QPRIMARY);
 }