Support 'TARGETS' in clipboard selections on MS-Windows

* src/w32select.c (Fw32_selection_targets): New function.

* lisp/term/w32-win.el (w32--get-selection): Call
'w32-selection-targets' to obtain the list of data formats
available in the clipboard.

1 files changed, 108 insertions, 0 deletions

diff --git a/src/w32select.c b/src/w32select.c
index a38a42ca050..1754534c3d3 100644
--- a/src/w32select.c
+++ b/src/w32select.c
@@ -1052,6 +1052,113 @@ frame's display, or the first available X display.  */)
   return Qnil;
 }
 
+/* Support enumerating available clipboard selection formats.  */
+
+DEFUN ("w32-selection-targets", Fw32_selection_targets, Sw32_selection_targets,
+       0, 2, 0,
+       doc: /* Return a vector of data formats available in the specified SELECTION.
+SELECTION should be the name of the selection in question, typically
+one of the symbols `PRIMARY', `SECONDARY', or `CLIPBOARD'.
+The symbol nil is the same as `PRIMARY', and t is the same as `SECONDARY'.
+
+TERMINAL should be a terminal object or a frame specifying the X
+server to query.  If omitted or nil, that stands for the selected
+frame's display, or the first available X display.
+
+This function currently ignores TERMINAL, and only returns non-nil
+for `CLIPBOARD'.  The return value is a vector of symbols, each symbol
+representing a data format that is currently available in the clipboard.  */)
+  (Lisp_Object selection, Lisp_Object terminal)
+{
+  /* Xlib-like names for standard Windows clipboard data formats.
+     They are in upper-case to mimic xselect.c.  A couple of the names
+     were changed to be more like their X counterparts.  */
+  static const char *stdfmt_name[] = {
+    "UNDEFINED",
+    "STRING",
+    "BITMAP",
+    "METAFILE",
+    "SYMLINK",
+    "DIF",
+    "TIFF",
+    "OEM_STRING",
+    "DIB",
+    "PALETTE",
+    "PENDATA",
+    "RIFF",
+    "WAVE",
+    "UTF8_STRING",
+    "ENHMETAFILE",
+    "FILE_NAMES", /* DND */
+    "LOCALE", /* not used */
+    "DIBV5"
+  };
+  CHECK_SYMBOL (selection);
+
+  /* Return nil for PRIMARY and SECONDARY selections; for CLIPBOARD, check
+     if the clipboard currently has valid text format contents.  */
+
+  if (EQ (selection, QCLIPBOARD))
+    {
+      Lisp_Object val = Qnil;
+
+      setup_config ();
+
+      if (OpenClipboard (NULL))
+        {
+          UINT format = 0;
+
+          /* Count how many formats are available.  We ignore the
+             CF_LOCALE format, and don't put it into the vector we
+             return, because CF_LOCALE is automatically created by
+             Windows for any text in the clipboard, so its presence in
+             the value will simply confuse.  */
+          int fmtcount = 0;
+          while ((format = EnumClipboardFormats (format)))
+            if (format != CF_LOCALE)
+              fmtcount++;
+
+          if (fmtcount > 0)
+            {
+              int i;
+
+              /* We generate a vector because that's what xselect.c
+                 does in this case.  */
+              val = Fmake_vector (make_number (fmtcount), Qnil);
+              /* Note: when stepping with GDB through this code, the
+                 loop below terminates immediately because
+                 EnumClipboardFormats for some reason returns with
+                 "Thread does not have a clipboard open" error.  */
+              for (i = 0, format = 0;
+                   (format = EnumClipboardFormats (format)) != 0; )
+                {
+                  const char *name;
+
+                  if (format == CF_LOCALE)
+                    continue;
+                  else if (format < CF_MAX)
+                    name = stdfmt_name[format];
+                  else
+                    {
+                      char fmt_name[256];
+
+                      if (!GetClipboardFormatName (format, fmt_name,
+                                                   sizeof (fmt_name)))
+                        continue;
+                      name = fmt_name;
+                    }
+                  ASET (val, i, intern (name));
+                  i++;
+                }
+            }
+          CloseClipboard ();
+        }
+      return val;
+    }
+  /* For PRIMARY and SECONDARY we cons the values in w32--get-selection.  */
+  return Qnil;
+}
+
 /* One-time init.  Called in the un-dumped Emacs, but not in the
    dumped version.  */
 
@@ -1061,6 +1168,7 @@ syms_of_w32select (void)
   defsubr (&Sw32_set_clipboard_data);
   defsubr (&Sw32_get_clipboard_data);
   defsubr (&Sw32_selection_exists_p);
+  defsubr (&Sw32_selection_targets);
 
   DEFVAR_LISP ("selection-coding-system", Vselection_coding_system,
                doc: /* Coding system for communicating with other programs.