(x_set_toolkit_scroll_bar_thumb) <USE_MOTIF>: Use a fixed-size

thumb (based on an ad-hoc estimate of 30 chars per line) to avoid
annoying flicker.
(xm_scroll_callback): Get rid of the now unnecessary kludge.
(XTread_socket): Mark it static.

2 files changed, 56 insertions, 62 deletions

diff --git a/src/ChangeLog b/src/ChangeLog
index 54e46245d30..99dda435bc1 100644
--- a/src/ChangeLog
+++ b/src/ChangeLog
@@ -1,5 +1,11 @@
 2002-03-13  Stefan Monnier  <monnier@cs.yale.edu>
 
+        * xterm.c (x_set_toolkit_scroll_bar_thumb) <USE_MOTIF>:
+        Use a fixed-size thumb (based on an ad-hoc estimate of 30 chars per
+        line) to avoid annoying flicker.
+        (xm_scroll_callback): Get rid of the now unnecessary kludge.
+        (XTread_socket): Mark it static.
+
         * xdisp.c (display_mode_element): Fix int/Lisp_Object mixup.
 
 2002-03-13  Kim F. Storm  <storm@cua.dk>
diff --git a/src/xterm.c b/src/xterm.c
index a0f942e44fc..37e41d0f34a 100644
--- a/src/xterm.c
+++ b/src/xterm.c
@@ -8553,31 +8553,10 @@ xm_scroll_callback (widget, client_data, call_data)
         XtVaGetValues (widget, XmNsliderSize, &slider_size, NULL);
         UNBLOCK_INPUT;
 
-        /* At the max position of the scroll bar, do a line-wise
-           movement.  Without doing anything, we would be called with
-           the same cs->value again and again.  If we want to make
-           sure that we can reach the end of the buffer, we have to do
-           something.
-
-           Implementation note: setting bar->dragging always to
-           cs->value gives a smoother movement at the max position.
-           Setting it to nil when doing line-wise movement gives
-           a better slider behavior. */
-        
-        if (cs->value + slider_size == XM_SB_MAX
-            || (dragging_down_p
-                && last_scroll_bar_part == scroll_bar_down_arrow))
-          {
-            part = scroll_bar_down_arrow;
-            bar->dragging = Qnil;
-          }
-        else
-          {
-            whole = XM_SB_RANGE;
-            portion = min (cs->value - XM_SB_MIN, XM_SB_MAX - slider_size);
-            part = scroll_bar_handle;
-            bar->dragging = make_number (cs->value);
-          }
+        whole = XM_SB_RANGE - slider_size;
+        portion = min (cs->value - XM_SB_MIN, whole);
+        part = scroll_bar_handle;
+        bar->dragging = make_number (cs->value);
       }
       break;
       
@@ -8880,7 +8859,27 @@ x_set_toolkit_scroll_bar_thumb (bar, portion, position, whole)
   Widget widget = SCROLL_BAR_X_WIDGET (FRAME_X_DISPLAY (f), bar);
   float top, shown;
 
-  if (whole == 0)
+  BLOCK_INPUT;
+
+#ifdef USE_MOTIF
+
+  /* We use an estimate of 30 chars per line rather than the real
+     `portion' value.  This has the disadvantage that the thumb size
+     is not very representative, but it makes our life a lot easier.
+     Otherwise, we have to constantly adjust the thumb size, which
+     we can't always do quickly enough: while dragging, the size of
+     the thumb might prevent the user from dragging the thumb all the
+     way to the end.  but Motif and some versions of Xaw3d don't allow
+     updating the thumb size while dragging.  Also, even if we can update
+     its size, the update will often happen too late.
+     If you don't believe it, check out revision 1.650 of xterm.c to see
+     what hoops we were going through and the still poor behavior we got.  */
+  portion = XFASTINT (XWINDOW (bar->window)->height) * 30;
+  /* When the thumb is at the bottom, position == whole.
+     So we need to increase `whole' to make space for the thumb.  */
+  whole += portion;
+
+  if (whole <= 0)
     top = 0, shown = 1;
   else
     {
@@ -8888,45 +8887,34 @@ x_set_toolkit_scroll_bar_thumb (bar, portion, position, whole)
       shown = (float) portion / whole;
     }
 
-  BLOCK_INPUT;
-
-#ifdef USE_MOTIF
-  {
-    int size, value;
-
-    /* Slider size.  Must be in the range [1 .. MAX - MIN] where MAX
-       is the scroll bar's maximum and MIN is the scroll bar's minimum
-       value.  */
-    size = shown * XM_SB_RANGE;
-    size = min (size, XM_SB_RANGE);
-    size = max (size, 1);
+  if (NILP (bar->dragging))
+    {
+      int size, value;
 
-    /* Position.  Must be in the range [MIN .. MAX - SLIDER_SIZE].  */
-    value = top * XM_SB_RANGE;
-    value = min (value, XM_SB_MAX - size);
-    value = max (value, XM_SB_MIN);
+      /* Slider size.  Must be in the range [1 .. MAX - MIN] where MAX
+         is the scroll bar's maximum and MIN is the scroll bar's minimum
+         value.  */
+      size = shown * XM_SB_RANGE;
+      size = min (size, XM_SB_RANGE);
+      size = max (size, 1);
 
-    if (NILP (bar->dragging))
+      /* Position.  Must be in the range [MIN .. MAX - SLIDER_SIZE].  */
+      value = top * XM_SB_RANGE;
+      value = min (value, XM_SB_MAX - size);
+      value = max (value, XM_SB_MIN);
+      
       XmScrollBarSetValues (widget, value, size, 0, 0, False);
-    else if (last_scroll_bar_part == scroll_bar_down_arrow)
-      /* This has the negative side effect that the slider value is
-         not what it would be if we scrolled here using line-wise or
-         page-wise movement.  */
-      XmScrollBarSetValues (widget, value, XM_SB_RANGE - value, 0, 0, False);
-    else
-      {
-        /* If currently dragging, only update the slider size.
-           This reduces flicker effects.  */
-        int old_value, old_size, increment, page_increment;
-        
-        XmScrollBarGetValues (widget, &old_value, &old_size,
-                              &increment, &page_increment);
-        XmScrollBarSetValues (widget, old_value,
-                              min (size, XM_SB_RANGE - old_value),
-                              0, 0, False);
-      }
-  }
+    }
 #else /* !USE_MOTIF i.e. use Xaw */
+
+  if (whole == 0)
+    top = 0, shown = 1;
+  else
+    {
+      top = (float) position / whole;
+      shown = (float) portion / whole;
+    }
+
   {
     float old_top, old_shown;
     Dimension height;
@@ -9953,7 +9941,7 @@ static struct x_display_info *next_noop_dpyinfo;
 
    EXPECTED is nonzero if the caller knows input is available.  */
 
-int
+static int
 XTread_socket (sd, bufp, numchars, expected)
      register int sd;
      /* register */ struct input_event *bufp;