From 2ef204e6071b985d5b8e5d1c25ca0b0abf5f9d31 Mon Sep 17 00:00:00 2001 From: "Owen W. Taylor" Date: Wed, 15 Jul 2015 12:38:38 -0400 Subject: [PATCH 1/2] GdkDisplayX11: Properly translate server timestamps from _NET_WM_FRAME_* messages When using frame times from _NET_WM_FRAME_DRAWN and _NET_WM_FRAME_TIMINGS, we were treating them as local monotonic times, but they are actually extended-precision versions of the server time, and need to be translated to monotonic times in the case where the X server and client aren't running on the same system. This fixes rendering stalls when using X over a remote ssh connection. https://bugzilla.gnome.org/show_bug.cgi?id=741800 --- gdk/x11/gdkdisplay-x11.c | 43 ++++++++++++++++++++++++++++++++++++++++++- gdk/x11/gdkdisplay-x11.h | 6 ++++++ 2 files changed, 48 insertions(+), 1 deletion(-) diff --git a/gdk/x11/gdkdisplay-x11.c b/gdk/x11/gdkdisplay-x11.c index 4fe7524..2fe2cd4 100644 --- a/gdk/x11/gdkdisplay-x11.c +++ b/gdk/x11/gdkdisplay-x11.c @@ -1096,6 +1096,47 @@ find_frame_timings (GdkFrameClock *clock, return NULL; } +/* _NET_WM_FRAME_DRAWN and _NET_WM_FRAME_TIMINGS messages represent time + * as a "high resolution server time" - this is the server time interpolated + * to microsecond resolution. The advantage of this time representation + * is that if X server is running on the same computer as a client, and + * the Xserver uses 'clock_gettime(CLOCK_MONOTONIC, ...)' for the server + * time, the client can detect this, and all such clients will share a + * a time representation with high accuracy. If there is not a common + * time source, then the time synchronization will be less accurate. + */ +gint64 +server_time_to_monotonic_time (GdkX11Display *display_x11, + gint64 server_time) +{ + if (display_x11->server_time_query_time == 0 || + (!display_x11->server_time_is_monotonic_time && + server_time > display_x11->server_time_query_time + 10*1000*1000)) /* 10 seconds */ + { + gint64 current_server_time = gdk_x11_get_server_time (display_x11->leader_gdk_window); + gint64 current_server_time_usec = (gint64)current_server_time * 1000; + gint64 current_monotonic_time = g_get_monotonic_time (); + display_x11->server_time_query_time = current_monotonic_time; + + /* If the server time is within a second of the monotonic time, + * we assume that they are identical. This seems like a big margin, + * but we want to be as robust as possible even if the system + * is under load and our processing of the server response is + * delayed. + */ + if (current_server_time_usec > current_monotonic_time - 1000*1000 && + current_server_time_usec < current_monotonic_time + 1000*1000) + display_x11->server_time_is_monotonic_time = TRUE; + + display_x11->server_time_offset = current_server_time_usec - current_monotonic_time; + } + + if (display_x11->server_time_is_monotonic_time) + return server_time; + else + return server_time - display_x11->server_time_offset; +} + GdkFilterReturn _gdk_wm_protocols_filter (GdkXEvent *xev, GdkEvent *event, @@ -1128,7 +1169,7 @@ _gdk_wm_protocols_filter (GdkXEvent *xev, guint32 d3 = xevent->xclient.data.l[3]; guint64 serial = ((guint64)d1 << 32) | d0; - gint64 frame_drawn_time = ((guint64)d3 << 32) | d2; + gint64 frame_drawn_time = server_time_to_monotonic_time (GDK_X11_DISPLAY (display), ((guint64)d3 << 32) | d2); gint64 refresh_interval, presentation_time; GdkFrameClock *clock = gdk_window_get_frame_clock (win); diff --git a/gdk/x11/gdkdisplay-x11.h b/gdk/x11/gdkdisplay-x11.h index 69ba890..d9305dd 100644 --- a/gdk/x11/gdkdisplay-x11.h +++ b/gdk/x11/gdkdisplay-x11.h @@ -124,6 +124,12 @@ struct _GdkX11Display GSList *error_traps; gint wm_moveresize_button; + + /* Translation between X server time and system-local monotonic time */ + gint64 server_time_query_time; + gint64 server_time_offset; + + guint server_time_is_monotonic_time : 1; }; struct _GdkX11DisplayClass -- 2.4.5