3 files changed, 115 insertions, 26 deletions

diff --git a/src/term.c b/src/term.c
index a5678f3fb7e..5fbfcc46107 100644
--- a/src/term.c
+++ b/src/term.c
@@ -93,12 +93,16 @@ int (*set_terminal_window_hook) ();
 
 int (*read_socket_hook) ();
 
-/* Return the current position of the mouse.  This should clear
-   mouse_moved until the next motion event arrives.  */
+/* Return the current position of the mouse.
+   Set `bar' to point to the scrollbar if the mouse movement started
+   in a scrollbar, or zero if it started elsewhere in the frame.
+   This should clear mouse_moved until the next motion event arrives.  */
 void (*mouse_position_hook) ( /* FRAME_PTR *f,
-                                        Lisp_Object *x,
-                                        Lisp_Object *y,
-                                        unsigned long *time */ );
+                                 struct scrollbar **bar,
+                                 enum scrollbar_part *part,
+                                 Lisp_Object *x,
+                                 Lisp_Object *y,
+                                 unsigned long *time */ );
 
 /* When reading from a minibuffer in a different frame, Emacs wants
    to shift the highlight from the selected frame to the minibuffer's
@@ -107,6 +111,38 @@ void (*mouse_position_hook) ( /* FRAME_PTR *f,
    the highlight.  */
 void (*frame_rehighlight_hook) ( /* FRAME_PTR f */ );
 
+/* Set vertical scollbar BAR to have its upper left corner at (TOP,
+   LEFT), and be LENGTH rows high.  Set its handle to indicate that we
+   are displaying PORTION characters out of a total of WHOLE
+   characters, starting at POSITION.  Return BAR.  If BAR is zero,
+   create a new scrollbar and return a pointer to it.  */
+struct scrollbar *(*set_vertical_scrollbar_hook)
+     ( /* struct scrollbar *BAR,
+          struct window *window,
+          int portion, int whole, int position */ );
+
+/* The following three hooks are used when we're doing a thorough
+   redisplay of the frame.  We don't explicitly know which scrollbars
+   are going to be deleted, because keeping track of when windows go
+   away is a real pain - can you say set-window-configuration?
+   Instead, we just assert at the beginning of redisplay that *all*
+   scrollbars are to be removed, and then save scrollbars from the
+   firey pit when we actually redisplay their window.  */
+
+/* Arrange for all scrollbars on FRAME to be removed at the next call
+   to `*judge_scrollbars_hook'.  A scrollbar may be spared if
+   `*redeem_scrollbar_hook' is applied to it before the judgement.  */
+void (*condemn_scrollbars_hook)( /* FRAME_PTR *FRAME */ );
+
+/* Unmark BAR for deletion in this judgement cycle.  */
+void (*redeem_scrollbar_hook)( /* struct scrollbar *BAR */ );
+
+/* Remove all scrollbars on FRAME that haven't been saved since the
+   last call to `*condemn_scrollbars_hook'.  */
+void (*judge_scrollbars_hook)( /* FRAME_PTR *FRAME */ );
+
+
+
 /* Strings, numbers and flags taken from the termcap entry.  */
 
 char *TS_ins_line;              /* termcap "al" */
@@ -1414,6 +1450,9 @@ It may be necessary to do `unsetenv TERMCAP' as well.\n",
   if (read_socket_hook)         /* Baudrate is somewhat */
                                 /* meaningless in this case */
     baud_rate = 9600;
+
+  FRAME_CAN_HAVE_SCROLLBARS (selected_frame) = 0;
+  FRAME_HAS_VERTICAL_SCROLLBARS (selected_frame) = 0;
 }
 
 /* VARARGS 1 */
diff --git a/src/termhooks.h b/src/termhooks.h
index c7f9d3d0909..63be5709999 100644
--- a/src/termhooks.h
+++ b/src/termhooks.h
@@ -45,9 +45,19 @@ extern int (*set_terminal_window_hook) ();
 
 extern int (*read_socket_hook) ();
 
-/* Return the current position of the mouse.  This should clear
-   mouse_moved until the next motion event arrives.  */
+enum scrollbar_part {
+  scrollbar_above_handle,
+  scrollbar_handle,
+  scrollbar_below_handle
+};
+
+/* Return the current position of the mouse.
+   Set `bar' to point to the scrollbar if the mouse movement started
+   in a scrollbar, or zero if it started elsewhere in the frame.
+   This should clear mouse_moved until the next motion event arrives.  */
 extern void (*mouse_position_hook) ( /* FRAME_PTR *f,
+                                        struct scrollbar **bar,
+                                        enum scrollbar_part *part,
                                         Lisp_Object *x,
                                         Lisp_Object *y,
                                         unsigned long *time */ );
@@ -62,6 +72,39 @@ extern int mouse_moved;
    X, this means that Emacs lies about where the focus is.  */
 extern void (*frame_rehighlight_hook) ( /* void */ );
 
+/* Set vertical scollbar BAR to have its upper left corner at (TOP,
+   LEFT), and be LENGTH rows high.  Set its handle to indicate that we
+   are displaying PORTION characters out of a total of WHOLE
+   characters, starting at POSITION.  Return BAR.  If BAR is zero,
+   create a new scrollbar and return a pointer to it.  */
+extern struct scrollbar *(*set_vertical_scrollbar_hook)
+     ( /* struct scrollbar *BAR,
+          struct window *window,
+          int portion, int whole, int position */ );
+
+
+/* The following three hooks are used when we're doing a thorough
+   redisplay of the frame.  We don't explicitly know which scrollbars
+   are going to be deleted, because keeping track of when windows go
+   away is a real pain - can you say set-window-configuration?
+   Instead, we just assert at the beginning of redisplay that *all*
+   scrollbars are to be removed, and then save scrollbars from the
+   firey pit when we actually redisplay their window.  */
+
+/* Arrange for all scrollbars on FRAME to be removed at the next call
+   to `*judge_scrollbars_hook'.  A scrollbar may be spared if
+   `*redeem_scrollbar_hook' is applied to it before the judgement.  */
+extern void (*condemn_scrollbars_hook)( /* FRAME_PTR *FRAME */ );
+
+/* Unmark BAR for deletion in this judgement cycle.  */
+extern void (*redeem_scrollbar_hook)( /* struct scrollbar *BAR */ );
+
+/* Remove all scrollbars on FRAME that haven't been saved since the
+   last call to `*condemn_scrollbars_hook'.  */
+extern void (*judge_scrollbars_hook)( /* FRAME_PTR *FRAME */ );
+
+
+
 /* If nonzero, send all terminal output characters to this stream also.  */
 extern FILE *termscript;
 
@@ -112,31 +155,32 @@ struct input_event {
                                    click occurred in.
                                    .timestamp gives a timestamp (in
                                    milliseconds) for the click.  */
-    scrollbar_click,            /* .code gives the number of the mouse
-                                   button that was clicked.
+
+    scrollbar_click,            /* .code gives the number of the mouse button
+                                   that was clicked.
+                                   .modifiers holds the state of the modifier
+                                   keys.
                                    .part is a lisp symbol indicating which
-                                   part of the scrollbar got clicked.  This
-                                   indicates whether the scroll bar was
-                                   horizontal or vertical.
-                                   .modifiers gives the state of the
-                                   modifier keys.
-                                   .x gives the distance from the start
-                                   of the scroll bar of the click; .y gives
-                                   the total length of the scroll bar.
-                                   .frame gives the frame the click
-                                   should apply to.
+                                   part of the scrollbar got clicked.
+                                   .scrollbar is a pointer to the scrollbar
+                                   clicked on.  Since redisplay may delete
+                                   scrollbars at any time, you may not assume
+                                   that this scrollbar still exists when you
+                                   dequeue this event.  You have to traverse
+                                   the window tree to make it's in a valid
+                                   window.
+                                   .x gives the distance from the start of the
+                                   scroll bar of the click; .y gives the total
+                                   length of the scroll bar.
+                                   .frame gives the frame the click should
+                                   apply to.
                                    .timestamp gives a timestamp (in
                                    milliseconds) for the click.  */
-#if 0
-    frame_selected,             /* The user has moved the focus to another
-                                   frame.
-                                   .frame is the frame that should become
-                                   selected at the next convenient time.  */
-#endif
   } kind;
   
   Lisp_Object code;
-  Lisp_Object part;
+  enum scrollbar_part part;
+  struct scrollbar *scrollbar;
 
 /* This is obviously wrong, but I'm not sure what else I should do.
    Obviously, this should be a FRAME_PTR.  But that would require that
diff --git a/src/window.h b/src/window.h
index 5bc3e73a912..b05386d978d 100644
--- a/src/window.h
+++ b/src/window.h
@@ -123,6 +123,12 @@ struct window
     Lisp_Object last_modified;
     /* Value of point at that time */
     Lisp_Object last_point;
+    /* Pointer to this window's vertical scrollbar, tagged as an
+       integer.  If this window is newly created and we haven't
+       displayed a scrollbar in it yet, or if the frame doesn't have
+       any scrollbars, this is nil.  */
+    Lisp_Object vertical_scrollbar;
+
 /* The rest are currently not used or only half used */
     /* Frame coords of point at that time */
     Lisp_Object last_point_x;