Add a system of clipboard identifiers.

This lays some groundwork for making PuTTY's cut and paste handling
more flexible in the area of which clipboard(s) it reads and writes,
if more than one is available on the system.

I've introduced a system of list macros which define an enumeration of
integer clipboard ids, some defined centrally in putty.h (at present
just a CLIP_NULL which never has any text in it, because that seems
like the sort of thing that will come in useful for configuring a
given copy or paste UI action to be ignored) and some defined per
platform. All the front end functions that copy and paste take a
clipboard id, and the Terminal structure is now configured at startup
to tell it which clipboard id it should paste from on a mouse click,
and which it should copy from on a selection.

However, I haven't actually added _real_ support for multiple X11
clipboards, in that the Unix front end supports a single CLIP_SYSTEM
regardless of whether it's in OS X or GTK mode. So this is currently a
NFC refactoring which does nothing but prepare the way for real
changes to come.

unix/gtkapp.c

@@ -147,7 +147,7 @@ static void paste_cb(GSimpleAction *action,
                      GVariant      *parameter,
                      gpointer       user_data)
 {
-    request_paste(user_data);
+    paste_menu_action(user_data);
 }
 
 static const GActionEntry win_actions[] = {

unix/gtkwin.c

@@ -1022,7 +1022,7 @@ gint key_event(GtkWidget *widget, GdkEventKey *event, gpointer data)
 #ifdef KEY_EVENT_DIAGNOSTICS
             debug((" - Shift-Insert paste\n"));
 #endif
-	    request_paste(inst);
+	    term_request_paste(inst->term, CLIP_SYSTEM);
 	    return TRUE;
 	}
 
@@ -2532,15 +2532,16 @@ static void clipboard_clear(GtkClipboard *clipboard, gpointer data)
     struct gui_data *inst = cdi->inst;
 
     if (inst->current_cdi == cdi) {
-        term_deselect(inst->term);
+        term_lost_clipboard_ownership(inst->term, CLIP_SYSTEM);
         inst->current_cdi = NULL;
     }
     sfree(cdi->pasteout_data_utf8);
     sfree(cdi);
 }
 
-void write_clip(void *frontend, wchar_t *data, int *attr, truecolour *truecolour,
-                int len, int must_deselect)
+void write_clip(void *frontend, int clipboard,
+                char_t *data, int *attr, truecolour *truecolour, int len,
+                int must_deselect)
 {
     struct gui_data *inst = (struct gui_data *)frontend;
     struct clipboard_data_instance *cdi;
@@ -2609,9 +2610,10 @@ static void clipboard_text_received(GtkClipboard *clipboard,
     sfree(paste);
 }
 
-void request_paste(void *frontend)
+void frontend_request_paste(void *frontend, int clipboard)
 {
     struct gui_data *inst = (struct gui_data *)frontend;
+    assert(clipboard == CLIP_SYSTEM);
     gtk_clipboard_request_text(inst->clipboard, clipboard_text_received, inst);
 }
 
@@ -2667,8 +2669,9 @@ static char *retrieve_cutbuffer(int *nbytes)
 #endif
 }
 
-void write_clip(void *frontend, wchar_t *data, int *attr, truecolour *truecolour,
-                int len, int must_deselect)
+void write_clip(void *frontend, int clipboard,
+                wchar_t *data, int *attr, truecolour *truecolour, int len,
+                int must_deselect)
 {
     struct gui_data *inst = (struct gui_data *)frontend;
     if (inst->pasteout_data)
@@ -2763,7 +2766,7 @@ void write_clip(void *frontend, wchar_t *data, int *attr, truecolour *truecolour
     }
 
     if (must_deselect)
-	term_deselect(inst->term);
+	term_lost_clipboard_ownership(inst->term, clipboard);
 }
 
 static void selection_get(GtkWidget *widget, GtkSelectionData *seldata,
@@ -2790,7 +2793,7 @@ static gint selection_clear(GtkWidget *widget, GdkEventSelection *seldata,
 {
     struct gui_data *inst = (struct gui_data *)data;
 
-    term_deselect(inst->term);
+    term_lost_clipboard_ownership(inst->term, CLIP_SYSTEM);
     if (inst->pasteout_data)
 	sfree(inst->pasteout_data);
     if (inst->pasteout_data_ctext)
@@ -2806,9 +2809,12 @@ static gint selection_clear(GtkWidget *widget, GdkEventSelection *seldata,
     return TRUE;
 }
 
-void request_paste(void *frontend)
+void frontend_request_paste(void *frontend, int clipboard)
 {
     struct gui_data *inst = (struct gui_data *)frontend;
+
+    assert(clipboard == CLIP_SYSTEM);
+
     /*
      * In Unix, pasting is asynchronous: all we can do at the
      * moment is to call gtk_selection_convert(), and when the data
@@ -3007,6 +3013,12 @@ void init_clipboard(struct gui_data *inst)
 
 #endif /* JUST_USE_GTK_CLIPBOARD_UTF8 */
 
+void paste_menu_action(void *frontend)
+{
+    struct gui_data *inst = (struct gui_data *)frontend;
+    term_request_paste(inst->term, CLIP_SYSTEM);
+}
+
 static void set_window_titles(struct gui_data *inst)
 {
     /*
@@ -4048,7 +4060,7 @@ void reset_terminal_menuitem(GtkMenuItem *item, gpointer data)
 void copy_all_menuitem(GtkMenuItem *item, gpointer data)
 {
     struct gui_data *inst = (struct gui_data *)data;
-    term_copyall(inst->term);
+    term_copyall(inst->term, CLIP_SYSTEM);
 }
 
 void special_menuitem(GtkMenuItem *item, gpointer data)
@@ -4922,6 +4934,8 @@ void new_session_window(Conf *conf, const char *geometry_string)
     inst->eventlogstuff = eventlogstuff_new();
 
     inst->term = term_init(inst->conf, &inst->ucsdata, inst);
+    inst->term->mouse_select_clipboard = CLIP_SYSTEM;
+    inst->term->mouse_paste_clipboard = CLIP_SYSTEM;
     inst->logctx = log_init(inst, inst->conf);
     term_provide_logctx(inst->term, inst->logctx);
 

unix/unix.h

@@ -119,6 +119,10 @@ unsigned long getticks(void);
  */
 #define FLAG_STDERR_TTY 0x1000
 
+#define PLATFORM_CLIPBOARDS(X)                      \
+    X(CLIP_SYSTEM, "system clipboard")              \
+    /* end of list */
+
 /* The per-session frontend structure managed by gtkwin.c */
 struct gui_data;
 
@@ -143,6 +147,9 @@ GtkWidget *make_gtk_toplevel_window(void *frontend);
 /* Defined in gtkcomm.c */
 void gtkcomm_setup(void);
 
+/* Defined in gtkwin.c */
+void paste_menu_action(void *frontend);
+
 /* Things pty.c needs from pterm.c */
 const char *get_x_display(void *frontend);
 int font_dimension(void *frontend, int which);/* 0 for width, 1 for height */