master ea5a0142ce: Respect inhibit-double-buffering on non-toolkit scroll bars

[Po Lu]

branch: master
commit ea5a0142ced33884a370e9a47f8035f303382ba7
Author: Po Lu <luangruo@yahoo.com>
Commit: Po Lu <luangruo@yahoo.com>

    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.
---
 src/xfns.c  | 14 +++++++++++++-
 src/xterm.c |  3 ++-
 2 files changed, 15 insertions(+), 2 deletions(-)

diff --git a/src/xfns.c b/src/xfns.c
index 65218b3fc0..e288f797fb 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 1d68d4e939..8642345549 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),