2 files changed, 83 insertions, 27 deletions

diff --git a/src/ChangeLog b/src/ChangeLog
index f668b87e4d8..a665944fa97 100644
--- a/src/ChangeLog
+++ b/src/ChangeLog
@@ -1,3 +1,12 @@
+2000-12-09  Miles Bader  <miles@gnu.org>
+
+        * window.c (Fpos_visible_in_window_p): Replace FULLY parameter
+        with PARTIALLY, inverting the sense.
+        (window_scroll_pixel_based): Scroll partially visible lines into
+        place if we hit the beginning or end of the buffer.
+        (displayed_window_lines): Don't include partially visible line at
+        bottom.
+
 2000-12-08  Gerd Moellmann  <gerd@gnu.org>
 
         * keymap.c (current_minor_maps): Use malloc.  Prevent a leak.
diff --git a/src/window.c b/src/window.c
index 708c0475636..3467be7edda 100644
--- a/src/window.c
+++ b/src/window.c
@@ -304,10 +304,11 @@ DEFUN ("pos-visible-in-window-p", Fpos_visible_in_window_p,
   Spos_visible_in_window_p, 0, 3, 0,
   "Return t if position POS is currently on the frame in WINDOW.\n\
 Return nil if that position is scrolled vertically out of view.\n\
-If FULLY is non-nil, then only return t when POS is completely visible.\n\
+If a character is only partially visible, nil is returned, unless the\n\
+optional argument PARTIALLY is non-nil.\n\
 POS defaults to point in WINDOW; WINDOW defaults to the selected window.")
-  (pos, window, fully)
-     Lisp_Object pos, window, fully;
+  (pos, window, partially)
+     Lisp_Object pos, window, partially;
 {
   register struct window *w;
   register int posint;
@@ -341,9 +342,9 @@ POS defaults to point in WINDOW; WINDOW defaults to the selected window.")
          that info.  This doesn't work for POSINT == end pos, because
          the window end pos is actually the position _after_ the last
          char in the window.  */
-      if (!NILP (fully))
+      if (NILP (partially))
         {
-          pos_visible_p (w, posint, &fully_p, !NILP (fully));
+          pos_visible_p (w, posint, &fully_p, NILP (partially));
           in_window = fully_p ? Qt : Qnil;
         }
       else
@@ -356,8 +357,8 @@ POS defaults to point in WINDOW; WINDOW defaults to the selected window.")
     in_window = Qnil;
   else
     {
-      if (pos_visible_p (w, posint, &fully_p, !NILP (fully)))
-        in_window = NILP (fully) || fully_p ? Qt : Qnil;
+      if (pos_visible_p (w, posint, &fully_p, NILP (partially)))
+        in_window = !NILP (partially) || fully_p ? Qt : Qnil;
       else
         in_window = Qnil;
     }
@@ -3885,6 +3886,8 @@ window_scroll_pixel_based (window, n, whole, noerror)
   Lisp_Object tem;
   int this_scroll_margin;
   int preserve_y;
+  /* True if we fiddled the window vscroll field without really scrolling.   */
+  int vscrolled = 0;
 
   SET_TEXT_POS_FROM_MARKER (start, w->start);
   
@@ -3944,23 +3947,53 @@ window_scroll_pixel_based (window, n, whole, noerror)
   if ((n > 0 && IT_CHARPOS (it) == ZV)
       || (n < 0 && IT_CHARPOS (it) == CHARPOS (start)))
     {
-      if (noerror)
-        return;
-      else if (IT_CHARPOS (it) == ZV)
-        Fsignal (Qend_of_buffer, Qnil);
+      if (IT_CHARPOS (it) == ZV)
+        {
+          if (it.current_y + it.max_ascent + it.max_descent
+              > it.last_visible_y)
+            /* The last line was only partially visible, make it fully
+               visible.  */
+            w->vscroll = 
+              it.last_visible_y
+              - it.current_y + it.max_ascent + it.max_descent;
+          else if (noerror)
+            return;
+          else
+            Fsignal (Qend_of_buffer, Qnil);
+        }
       else
-        Fsignal (Qbeginning_of_buffer, Qnil);
+        {
+          if (w->vscroll != 0)
+            /* The first line was only partially visible, make it fully
+               visible. */
+            w->vscroll = 0;
+          else if (noerror)
+            return;
+          else
+            Fsignal (Qbeginning_of_buffer, Qnil);
+        }
+
+      /* If control gets here, then we vscrolled.  */
+
+      XBUFFER (w->buffer)->prevent_redisplay_optimizations_p = 1;
+
+      /* Don't try to change the window start below.  */
+      vscrolled = 1;
     }
 
-  /* Set the window start, and set up the window for redisplay.  */
-  set_marker_restricted (w->start, make_number (IT_CHARPOS (it)), w->buffer);
-  w->start_at_line_beg = Fbolp ();
-  w->update_mode_line = Qt;
-  XSETFASTINT (w->last_modified, 0);
-  XSETFASTINT (w->last_overlay_modified, 0);
-  /* Set force_start so that redisplay_window will run the
-     window-scroll-functions.  */
-  w->force_start = Qt;
+  if (! vscrolled)
+    {
+      /* Set the window start, and set up the window for redisplay.  */
+      set_marker_restricted (w->start, make_number (IT_CHARPOS (it)),
+                             w->buffer);
+      w->start_at_line_beg = Fbolp ();
+      w->update_mode_line = Qt;
+      XSETFASTINT (w->last_modified, 0);
+      XSETFASTINT (w->last_overlay_modified, 0);
+      /* Set force_start so that redisplay_window will run the
+         window-scroll-functions.  */
+      w->force_start = Qt;
+    }
   
   it.current_y = it.vpos = 0;
   
@@ -3988,18 +4021,30 @@ window_scroll_pixel_based (window, n, whole, noerror)
         }
       else if (n < 0)
         {
+          int charpos, bytepos;
+
           /* We moved the window start towards BEGV, so PT may be now
              in the scroll margin at the bottom.  */
           move_it_to (&it, PT, -1,
                       it.last_visible_y - this_scroll_margin - 1, -1,
                       MOVE_TO_POS | MOVE_TO_Y);
+
+          /* Save our position, in case it's correct.  */
+          charpos = IT_CHARPOS (it);
+          bytepos = IT_BYTEPOS (it);
       
-          /* Don't put point on a partially visible line at the end.  */
-          if (it.current_y + it.max_ascent + it.max_descent
-              > it.last_visible_y)
-            move_it_by_lines (&it, -1, 0);
-      
-          SET_PT_BOTH (IT_CHARPOS (it), IT_BYTEPOS (it));
+          /* See if point is on a partially visible line at the end.  */
+          move_it_by_lines (&it, 1, 1);
+          if (it.current_y > it.last_visible_y)
+            /* The last line was only partially visible, so back up two
+               lines to make sure we're on a fully visible line.  */
+            {
+              move_it_by_lines (&it, -2, 0);
+              SET_PT_BOTH (IT_CHARPOS (it), IT_BYTEPOS (it));
+            }
+          else
+            /* No, the position we saved is OK, so use it.  */
+            SET_PT_BOTH (charpos, bytepos);
         }
     }
 }
@@ -4437,9 +4482,11 @@ displayed_window_lines (w)
       int lines = (rest + CANON_Y_UNIT (f) - 1) / CANON_Y_UNIT (f);
       it.vpos += lines;
     }
+#if 0
   else if (it.current_y < height && bottom_y > height)
     /* Partially visible line at the bottom.  */
     ++it.vpos;
+#endif
   
   return it.vpos;
 }