(XTset_vertical_scroll_bar): Improve handling of scroll

bars with fractional column width.  If scroll bar separates two
windows, move it towards the window it belongs to.  Only update
the padding area below the scroll bar widget when necessary,
i.e. when scroll bar widget is created, moved, or resized.

1 files changed, 15 insertions, 8 deletions

diff --git a/src/xterm.c b/src/xterm.c
index acbb30ef21b..97e21d1f255 100644
--- a/src/xterm.c
+++ b/src/xterm.c
@@ -5046,9 +5046,15 @@ XTset_vertical_scroll_bar (w, portion, whole, position)
   /* Compute the left edge of the scroll bar.  */
 #ifdef USE_TOOLKIT_SCROLL_BARS
   if (WINDOW_HAS_VERTICAL_SCROLL_BAR_ON_RIGHT (w))
-    sb_left = left + width - sb_width - (width - sb_width) / 2;
+    sb_left = (left +
+               (WINDOW_RIGHTMOST_P (w)
+                ? width - sb_width - (width - sb_width) / 2
+                : 0));
   else
-    sb_left = left + (width - sb_width) / 2;
+    sb_left = (left +
+               (WINDOW_LEFTMOST_P (w)
+                ? (width - sb_width) / 2
+                : width - sb_width));
 #else
   if (WINDOW_HAS_VERTICAL_SCROLL_BAR_ON_RIGHT (w))
     sb_left = left + width - sb_width;
@@ -5101,19 +5107,20 @@ XTset_vertical_scroll_bar (w, portion, whole, position)
                                  width);
 #else /* not USE_GTK */
 
-      /* Since toolkit scroll bars are smaller than the space reserved
-         for them on the frame, we have to clear "under" them.  */
-      if (width > 0 && height > 0)
-        x_clear_area (FRAME_X_DISPLAY (f), FRAME_X_WINDOW (f),
-                          left, top, width, height, False);
       /* Move/size the scroll bar widget.  */
       if (mask)
+        {
+          /* Since toolkit scroll bars are smaller than the space reserved
+             for them on the frame, we have to clear "under" them.  */
+          if (width > 0 && height > 0)
+            x_clear_area (FRAME_X_DISPLAY (f), FRAME_X_WINDOW (f),
+                          left, top, width, height, False);
           XtConfigureWidget (SCROLL_BAR_X_WIDGET (FRAME_X_DISPLAY (f), bar),
                              sb_left + VERTICAL_SCROLL_BAR_WIDTH_TRIM,
                              top,
                              sb_width - VERTICAL_SCROLL_BAR_WIDTH_TRIM * 2,
                              max (height, 1), 0);
-
+        }
 #endif /* not USE_GTK */
 #else /* not USE_TOOLKIT_SCROLL_BARS */