Implement selection ownership on Haiku

* lisp/term/haiku-win.el (haiku-selection-owner-p): New
declaration.
(gui-backend-selection-owner-p): Implement using newly exposed
primitive.

* src/haiku_select.cc
(count_clipboard, count_primary, count_secondary): New
variables for tracking selection ownership.
(BClipboard_set_system_data):
(BClipboard_set_primary_selection_data):
(BClipboard_set_secondary_selection_data): Set ownership
variables.
(BClipboard_owns_clipboard):
(BClipboard_owns_primary):
(BClipboard_owns_secondary): New functions.

* src/haikuselect.c (Fhaiku_selection_owner_p): New function.
(syms_of_haikuselect): Define new subr.
* src/haikuselect.h: New prototypes.

4 files changed, 70 insertions, 3 deletions

diff --git a/lisp/term/haiku-win.el b/lisp/term/haiku-win.el
index 739ea9fdfce..a5cde929f96 100644
--- a/lisp/term/haiku-win.el
+++ b/lisp/term/haiku-win.el
@@ -50,6 +50,7 @@
 (declare-function haiku-selection-data "haikuselect.c")
 (declare-function haiku-selection-put "haikuselect.c")
 (declare-function haiku-selection-targets "haikuselect.c")
+(declare-function haiku-selection-owner-p "haikuselect.c")
 (declare-function haiku-put-resource "haikufns.c")
 
 (defun haiku--handle-x-command-line-resources (command-line-resources)
@@ -105,9 +106,8 @@ If TYPE is nil, return \"text/plain\"."
                                               &context (window-system haiku))
   (haiku-selection-data selection "text/plain"))
 
-(cl-defmethod gui-backend-selection-owner-p (_
-                                             &context (window-system haiku))
-  t)
+(cl-defmethod gui-backend-selection-owner-p (selection &context (window-system haiku))
+  (haiku-selection-owner-p selection))
 
 (declare-function haiku-read-file-name "haikufns.c")
 
diff --git a/src/haiku_select.cc b/src/haiku_select.cc
index 041e244f3ea..d39000d8bbe 100644
--- a/src/haiku_select.cc
+++ b/src/haiku_select.cc
@@ -29,6 +29,9 @@ along with GNU Emacs.  If not, see <https://www.gnu.org/licenses/>.  */
 static BClipboard *primary = NULL;
 static BClipboard *secondary = NULL;
 static BClipboard *system_clipboard = NULL;
+static unsigned long count_clipboard = 0;
+static unsigned long count_primary = 0;
+static unsigned long count_secondary = 0;
 
 int selection_state_flag;
 
@@ -174,6 +177,7 @@ BClipboard_set_system_data (const char *type, const char *data,
     return;
 
   BClipboard_set_data (system_clipboard, type, data, len, clear);
+  count_clipboard = system_clipboard->SystemCount ();
 }
 
 void
@@ -184,6 +188,7 @@ BClipboard_set_primary_selection_data (const char *type, const char *data,
     return;
 
   BClipboard_set_data (primary, type, data, len, clear);
+  count_primary = primary->SystemCount ();
 }
 
 void
@@ -194,6 +199,7 @@ BClipboard_set_secondary_selection_data (const char *type, const char *data,
     return;
 
   BClipboard_set_data (secondary, type, data, len, clear);
+  count_secondary = secondary->SystemCount ();
 }
 
 void
@@ -220,6 +226,27 @@ BClipboard_secondary_targets (char **buf, int len)
   BClipboard_get_targets (secondary, buf, len);
 }
 
+bool
+BClipboard_owns_clipboard (void)
+{
+  return (count_clipboard
+	  == system_clipboard->SystemCount ());
+}
+
+bool
+BClipboard_owns_primary (void)
+{
+  return (count_primary
+	  == primary->SystemCount ());
+}
+
+bool
+BClipboard_owns_secondary (void)
+{
+  return (count_secondary
+	  == secondary->SystemCount ());
+}
+
 void
 init_haiku_select (void)
 {
diff --git a/src/haikuselect.c b/src/haikuselect.c
index 2e619c69f7a..e65ab827c51 100644
--- a/src/haikuselect.c
+++ b/src/haikuselect.c
@@ -166,6 +166,36 @@ clipboard.  */)
   return Qnil;
 }
 
+DEFUN ("haiku-selection-owner-p", Fhaiku_selection_owner_p, Shaiku_selection_owner_p,
+       0, 1, 0,
+       doc: /* Whether the current Emacs process owns the given SELECTION.
+The arg should be the name of the selection in question, typically one
+of the symbols `PRIMARY', `SECONDARY', or `CLIPBOARD'.  For
+convenience, the symbol nil is the same as `PRIMARY', and t is the
+same as `SECONDARY'.  */)
+  (Lisp_Object selection)
+{
+  bool value;
+
+  if (NILP (selection))
+    selection = QPRIMARY;
+  else if (EQ (selection, Qt))
+    selection = QSECONDARY;
+
+  block_input ();
+  if (EQ (selection, QPRIMARY))
+    value = BClipboard_owns_primary ();
+  else if (EQ (selection, QSECONDARY))
+    value = BClipboard_owns_secondary ();
+  else if (EQ (selection, QCLIPBOARD))
+    value = BClipboard_owns_clipboard ();
+  else
+    value = false;
+  unblock_input ();
+
+  return value ? Qt : Qnil;
+}
+
 void
 syms_of_haikuselect (void)
 {
@@ -179,4 +209,5 @@ syms_of_haikuselect (void)
   defsubr (&Shaiku_selection_data);
   defsubr (&Shaiku_selection_put);
   defsubr (&Shaiku_selection_targets);
+  defsubr (&Shaiku_selection_owner_p);
 }
diff --git a/src/haikuselect.h b/src/haikuselect.h
index 80f33c6ed25..566aae596f6 100644
--- a/src/haikuselect.h
+++ b/src/haikuselect.h
@@ -66,6 +66,15 @@ extern "C"
   extern void
   BClipboard_secondary_targets (char **buf, int len);
 
+  extern bool
+  BClipboard_owns_clipboard (void);
+
+  extern bool
+  BClipboard_owns_primary (void);
+
+  extern bool
+  BClipboard_owns_secondary (void);
+
   /* Free the returned data.  */
   extern void BClipboard_free_data (void *ptr);
 #ifdef __cplusplus