master 1c90138651: Improve performance of other_frames and XTfullscreen_hook

[Po Lu]

branch: master
commit 1c9013865183f0ea21218602917b5c16ecef465d
Author: Po Lu <luangruo@yahoo.com>
Commit: Po Lu <luangruo@yahoo.com>

    Improve performance of other_frames and XTfullscreen_hook
    
    * src/frame.c (other_frames):
    * src/xterm.c (XTfullscreen_hook, x_check_fullscreen)
    (x_set_window_size_1): Avoid extraneous calls to x_sync.
---
 src/frame.c | 49 +++++++++++++++++++++++++++++++++++++++++++++++++
 src/xterm.c | 20 +++++++-------------
 2 files changed, 56 insertions(+), 13 deletions(-)

diff --git a/src/frame.c b/src/frame.c
index 05106a6c75..7d902dabd4 100644
--- a/src/frame.c
+++ b/src/frame.c
@@ -1892,12 +1892,61 @@ other_frames (struct frame *f, bool invisible, bool 
force)
 
       if (f != f1)
        {
+         /* The following code is defined out because it is
+            responsible for a performance drop under X connections
+            over a network, and its purpose is unclear.  XSync does
+            not handle events (or call any callbacks defined by
+            Emacs), and as such it should not note any "recent change
+            in visibility".
+
+            When writing new code, please try as hard as possible to
+            avoid calls that require a roundtrip to the X server.
+            When such calls are inevitable, use the XCB library to
+            handle multiple consecutive requests with a data reply in
+            a more asynchronous fashion.  The following code
+            demonstrates why:
+
+              rc = XGetWindowProperty (dpyinfo->display, window, ...
+              status = XGrabKeyboard (dpyinfo->display, ...
+
+            here, `XGetWindowProperty' will wait for a reply from the
+            X server before returning, and thus allowing Emacs to
+            make the XGrabKeyboard request, which in itself also
+            requires waiting a reply.  When XCB is available, this
+            code could be written:
+
+#ifdef HAVE_XCB
+              xcb_get_property_cookie_t cookie1;
+              xcb_get_property_reply_t *reply1;
+              xcb_grab_keyboard_cookie_t cookie2;
+              xcb_grab_keyboard_reply_t *reply2;
+
+              cookie1 = xcb_get_property (dpyinfo->xcb_connection, window, ...
+              cookie2 = xcb_grab_keyboard (dpyinfo->xcb_connection, ...
+              reply1 = xcb_get_property_reply (dpyinfo->xcb_connection,
+                                               cookie1);
+              reply2 = xcb_grab_keyboard_reply (dpyinfo->xcb_connection,
+                                               cookie2);
+#endif
+
+            In this code, the GetProperty and GrabKeyboard requests
+            are made simultaneously, and replies are then obtained
+            from the server at once, avoiding the extraneous
+            roundtrip to the X server after the call to
+            `XGetWindowProperty'.
+
+            However, please keep an alternative implementation
+            available for use when Emacs is built without XCB.  */
+
+#if 0
          /* Verify that we can still talk to the frame's X window, and
             note any recent change in visibility.  */
 #ifdef HAVE_X_WINDOWS
          if (FRAME_WINDOW_P (f1))
            x_sync (f1);
 #endif
+#endif
+
          if (!FRAME_TOOLTIP_P (f1)
              /* Tooltips and child frames count neither for
                 invisibility nor for deletions.  */
diff --git a/src/xterm.c b/src/xterm.c
index c775f19985..37b907ee9d 100644
--- a/src/xterm.c
+++ b/src/xterm.c
@@ -27202,13 +27202,12 @@ do_ewmh_fullscreen (struct frame *f)
 static void
 XTfullscreen_hook (struct frame *f)
 {
-  if (FRAME_VISIBLE_P (f))
-    {
-      block_input ();
-      x_check_fullscreen (f);
-      x_sync (f);
-      unblock_input ();
-    }
+  if (!FRAME_VISIBLE_P (f))
+    return;
+
+  block_input ();
+  x_check_fullscreen (f);
+  unblock_input ();
 }
 
 
@@ -27302,10 +27301,7 @@ x_check_fullscreen (struct frame *f)
       if (FRAME_VISIBLE_P (f))
        x_wait_for_event (f, ConfigureNotify);
       else
-       {
-         change_frame_size (f, width, height, false, true, false);
-         x_sync (f);
-       }
+       change_frame_size (f, width, height, false, true, false);
     }
 
   /* `x_net_wm_state' might have reset the fullscreen frame parameter,
@@ -27519,8 +27515,6 @@ x_set_window_size_1 (struct frame *f, bool 
change_gravity,
       adjust_frame_size (f, FRAME_PIXEL_TO_TEXT_WIDTH (f, width),
                         FRAME_PIXEL_TO_TEXT_HEIGHT (f, height),
                         5, 0, Qx_set_window_size_1);
-
-      x_sync (f);
     }
 }