Respect inhibit-double-buffering on non-toolkit scroll bars

* src/xfns.c (x_set_inhibit_double_buffering): Force scroll bars
to be re-created on builds without toolkit scroll bars.

* src/xterm.c (x_scroll_bar_create): Don't initialize back
buffer if double buffering is disabled for the frame.

2 files changed, 15 insertions, 2 deletions

diff --git a/src/xfns.c b/src/xfns.c
index 65218b3fc07..e288f797fbd 100644
--- a/src/xfns.c
+++ b/src/xfns.c
@@ -818,7 +818,19 @@ x_set_inhibit_double_buffering (struct frame *f,
          and after any potential change.  One of the calls will end up
          being a no-op.  */
       if (want_double_buffering != was_double_buffered)
-        font_drop_xrender_surfaces (f);
+        {
+          font_drop_xrender_surfaces (f);
+
+          /* Scroll bars decide whether or not to use a back buffer
+             based on the value of this frame parameter, so destroy
+             all scroll bars.  */
+#ifndef USE_TOOLKIT_SCROLL_BARS
+          if (FRAME_TERMINAL (f)->condemn_scroll_bars_hook)
+            FRAME_TERMINAL (f)->condemn_scroll_bars_hook (f);
+          if (FRAME_TERMINAL (f)->judge_scroll_bars_hook)
+            FRAME_TERMINAL (f)->judge_scroll_bars_hook (f);
+#endif
+        }
       if (FRAME_X_DOUBLE_BUFFERED_P (f) && !want_double_buffering)
         tear_down_x_back_buffer (f);
       else if (!FRAME_X_DOUBLE_BUFFERED_P (f) && want_double_buffering)
diff --git a/src/xterm.c b/src/xterm.c
index 1d68d4e9393..8642345549c 100644
--- a/src/xterm.c
+++ b/src/xterm.c
@@ -8583,7 +8583,8 @@ x_scroll_bar_create (struct window *w, int top, int left,
                              /* Attributes.  */
                             mask, &a);
 #ifdef HAVE_XDBE
-    if (FRAME_DISPLAY_INFO (f)->supports_xdbe)
+    if (FRAME_DISPLAY_INFO (f)->supports_xdbe
+        && FRAME_X_DOUBLE_BUFFERED_P (f))
       {
         x_catch_errors (FRAME_X_DISPLAY (f));
         drawable = XdbeAllocateBackBufferName (FRAME_X_DISPLAY (f),