From 388ed4984586f96250934a025b1c78915c4cd856 Mon Sep 17 00:00:00 2001

From: =?UTF-8?q?Jonas=20=C3=85dahl?= <jadahl@gmail.com>

Date: Thu, 24 Oct 2019 21:19:36 +0200

Subject: [PATCH 1/2] display: Move finishing of touch sequence to the backend

We need to manipulate an X11 grab when a touch sequence ends; move that

logic to where it belongs - in the X11 backend.

https://gitlab.gnome.org/GNOME/mutter/merge_requests/886

---

 src/backends/meta-backend-private.h     | 16 ++++++++++++

 src/backends/meta-backend.c             | 14 +++++++++++

 src/backends/x11/meta-backend-x11.c     | 23 +++++++++++++++++

 src/core/display.c                      | 33 +++++++++++--------------

 src/core/meta-gesture-tracker-private.h |  7 +-----

 src/core/meta-gesture-tracker.c         |  1 +

 6 files changed, 70 insertions(+), 24 deletions(-)

diff --git a/src/backends/meta-backend-private.h b/src/backends/meta-backend-private.h

index a25275499..7f4a4ea0f 100644

--- a/src/backends/meta-backend-private.h

+++ b/src/backends/meta-backend-private.h

@@ -51,6 +51,14 @@

 #define META_TYPE_BACKEND (meta_backend_get_type ())

 G_DECLARE_DERIVABLE_TYPE (MetaBackend, meta_backend, META, BACKEND, GObject)

+typedef enum _MetaSequenceState

+{

+  META_SEQUENCE_NONE,

+  META_SEQUENCE_ACCEPTED,

+  META_SEQUENCE_REJECTED,

+  META_SEQUENCE_PENDING_END

+} MetaSequenceState;

+

 struct _MetaBackendClass

 {

   GObjectClass parent_class;

@@ -73,6 +81,10 @@ struct _MetaBackendClass

                               int          device_id,

                               uint32_t     timestamp);

+  void (* finish_touch_sequence) (MetaBackend          *backend,

+                                  ClutterEventSequence *sequence,

+                                  MetaSequenceState     state);

+

   void (* warp_pointer) (MetaBackend *backend,

                          int          x,

                          int          y);

@@ -134,6 +146,10 @@ gboolean meta_backend_ungrab_device (MetaBackend *backend,

                                      int          device_id,

                                      uint32_t     timestamp);

+void meta_backend_finish_touch_sequence (MetaBackend          *backend,

+                                         ClutterEventSequence *sequence,

+                                         MetaSequenceState     state);

+

 void meta_backend_warp_pointer (MetaBackend *backend,

                                 int          x,

                                 int          y);

diff --git a/src/backends/meta-backend.c b/src/backends/meta-backend.c

index ce7e385b9..fb4f69fe6 100644

--- a/src/backends/meta-backend.c

+++ b/src/backends/meta-backend.c

@@ -846,6 +846,20 @@ meta_backend_ungrab_device (MetaBackend *backend,

   return META_BACKEND_GET_CLASS (backend)->ungrab_device (backend, device_id, timestamp);

 }

+/**

+ * meta_backend_finish_touch_sequence: (skip)

+ */

+void

+meta_backend_finish_touch_sequence (MetaBackend          *backend,

+                                    ClutterEventSequence *sequence,

+                                    MetaSequenceState     state)

+{

+  if (META_BACKEND_GET_CLASS (backend)->finish_touch_sequence)

+    META_BACKEND_GET_CLASS (backend)->finish_touch_sequence (backend,

+                                                             sequence,

+                                                             state);

+}

+

 /**

  * meta_backend_warp_pointer: (skip)

  */

diff --git a/src/backends/x11/meta-backend-x11.c b/src/backends/x11/meta-backend-x11.c

index 2b131d2d0..2835d47d6 100644

--- a/src/backends/x11/meta-backend-x11.c

+++ b/src/backends/x11/meta-backend-x11.c

@@ -583,6 +583,28 @@ meta_backend_x11_ungrab_device (MetaBackend *backend,

   return (ret == Success);

 }

+static void

+meta_backend_x11_finish_touch_sequence (MetaBackend          *backend,

+                                        ClutterEventSequence *sequence,

+                                        MetaSequenceState     state)

+{

+  MetaBackendX11 *x11 = META_BACKEND_X11 (backend);

+  MetaBackendX11Private *priv = meta_backend_x11_get_instance_private (x11);

+  int event_mode;

+

+  if (state == META_SEQUENCE_ACCEPTED)

+    event_mode = XIAcceptTouch;

+  else if (state == META_SEQUENCE_REJECTED)

+    event_mode = XIRejectTouch;

+  else

+    g_return_if_reached ();

+

+  XIAllowTouchEvents (priv->xdisplay,

+                      META_VIRTUAL_CORE_POINTER_ID,

+                      clutter_x11_event_sequence_get_touch_detail (sequence),

+                      DefaultRootWindow (priv->xdisplay), event_mode);

+}

+

 static void

 meta_backend_x11_warp_pointer (MetaBackend *backend,

                                int          x,

@@ -768,6 +790,7 @@ meta_backend_x11_class_init (MetaBackendX11Class *klass)

   backend_class->post_init = meta_backend_x11_post_init;

   backend_class->grab_device = meta_backend_x11_grab_device;

   backend_class->ungrab_device = meta_backend_x11_ungrab_device;

+  backend_class->finish_touch_sequence = meta_backend_x11_finish_touch_sequence;

   backend_class->warp_pointer = meta_backend_x11_warp_pointer;

   backend_class->get_current_logical_monitor = meta_backend_x11_get_current_logical_monitor;

   backend_class->get_keymap = meta_backend_x11_get_keymap;

diff --git a/src/core/display.c b/src/core/display.c

index e7dd4534b..d4775cec3 100644

--- a/src/core/display.c

+++ b/src/core/display.c

@@ -55,6 +55,7 @@

 #include "backends/x11/meta-backend-x11.h"

 #include "backends/meta-stage-private.h"

 #include "backends/meta-input-settings-private.h"

+#include "backends/meta-backend-private.h"

 #include <clutter/x11/clutter-x11.h>

 #ifdef HAVE_RANDR

@@ -533,27 +534,23 @@ gesture_tracker_state_changed (MetaGestureTracker   *tracker,

                                MetaSequenceState     state,

                                MetaDisplay          *display)

 {

-  if (meta_is_wayland_compositor ())

+  switch (state)

     {

-      if (state == META_SEQUENCE_ACCEPTED)

-        meta_display_cancel_touch (display);

-    }

-  else

-    {

-      MetaBackendX11 *backend = META_BACKEND_X11 (meta_get_backend ());

-      int event_mode;

+    case META_SEQUENCE_NONE:

+    case META_SEQUENCE_PENDING_END:

+      return;

+    case META_SEQUENCE_ACCEPTED:

+      meta_display_cancel_touch (display);

-      if (state == META_SEQUENCE_ACCEPTED)

-        event_mode = XIAcceptTouch;

-      else if (state == META_SEQUENCE_REJECTED)

-        event_mode = XIRejectTouch;

-      else

-        return;

+      /* Intentional fall-through */

+    case META_SEQUENCE_REJECTED:

+      {

+        MetaBackend *backend;

-      XIAllowTouchEvents (meta_backend_x11_get_xdisplay (backend),

-                          META_VIRTUAL_CORE_POINTER_ID,

-                          clutter_x11_event_sequence_get_touch_detail (sequence),

-                          DefaultRootWindow (display->xdisplay), event_mode);

+        backend = meta_get_backend ();

+        meta_backend_finish_touch_sequence (backend, sequence, state);

+        break;

+      }

     }

 }

diff --git a/src/core/meta-gesture-tracker-private.h b/src/core/meta-gesture-tracker-private.h

index 0e39af27f..b4fb02a1e 100644

--- a/src/core/meta-gesture-tracker-private.h

+++ b/src/core/meta-gesture-tracker-private.h

@@ -38,12 +38,7 @@

 typedef struct _MetaGestureTracker MetaGestureTracker;

 typedef struct _MetaGestureTrackerClass MetaGestureTrackerClass;

-typedef enum {

-  META_SEQUENCE_NONE,

-  META_SEQUENCE_ACCEPTED,

-  META_SEQUENCE_REJECTED,

-  META_SEQUENCE_PENDING_END

-} MetaSequenceState;

+typedef enum _MetaSequenceState MetaSequenceState;

 struct _MetaGestureTracker

 {

diff --git a/src/core/meta-gesture-tracker.c b/src/core/meta-gesture-tracker.c

index e3b702f56..1313aad6d 100644

--- a/src/core/meta-gesture-tracker.c

+++ b/src/core/meta-gesture-tracker.c

@@ -31,6 +31,7 @@

 #include "config.h"

 #include "meta-gesture-tracker-private.h"

 #include "meta-surface-actor.h"

+#include "meta-backend-private.h"

 #define DISTANCE_THRESHOLD 30

-- 

2.23.0

From 75cf52ac533675ecf5d3542e9fba2937a56bfefd Mon Sep 17 00:00:00 2001

From: =?UTF-8?q?Jonas=20=C3=85dahl?= <jadahl@gmail.com>

Date: Fri, 25 Oct 2019 10:06:55 +0200

Subject: [PATCH 2/2] x11: Limit touch replay pointer events to when replaying

When a touch sequence was rejected, the emulated pointer events would be

replayed with old timestamps. This caused issues with grabs as they

would be ignored due to being too old. This was mitigated by making sure

device event timestamps never travelled back in time by tampering with

any event that had a timestamp seemingly in the past.

This failed when the most recent timestamp that had been received were

much older than the timestamp of the new event. This could for example

happen when a session was left not interacted with for 40+ days or so;

when interacted with again, as any new timestamp would according to

XSERVER_TIME_IS_BEFORE() still be in the past compared to the "most

recent" one. The effect is that we'd always use the `latest_evtime` for

all new device events without ever updating it.

The end result of this was that passive grabs would become active when

interacted with, but would then newer be released, as the timestamps to

XIAllowEvents() would out of date, resulting in the desktop effectively

freezing, as the Shell would have an active pointer grab.

To avoid the situation where we get stuck with an old `latest_evtime`

timestamp, limit the tampering with device event timestamp to 1) only

pointer events, and 2) only during the replay sequence. The second part

is implemented by sending an asynchronous message via the X server after

rejecting a touch sequence, only potentially tampering with the device

event timestamps until the reply. This should avoid the stuck timestamp

as in those situations, we'll always have a relatively up to date

`latest_evtime` meaning XSERVER_TIME_IS_BEFORE() will not get confused.

https://gitlab.gnome.org/GNOME/mutter/merge_requests/886

---

 src/backends/x11/meta-backend-x11.c | 71 +++++++++++++++++++++++------

 1 file changed, 58 insertions(+), 13 deletions(-)

diff --git a/src/backends/x11/meta-backend-x11.c b/src/backends/x11/meta-backend-x11.c

index 2835d47d6..3f8645e93 100644

--- a/src/backends/x11/meta-backend-x11.c

+++ b/src/backends/x11/meta-backend-x11.c

@@ -60,6 +60,10 @@ struct _MetaBackendX11Private

   XSyncAlarm user_active_alarm;

   XSyncCounter counter;

+  int current_touch_replay_sync_serial;

+  int pending_touch_replay_sync_serial;

+  Atom touch_replay_sync_atom;

+

   int xinput_opcode;

   int xinput_event_base;

   int xinput_error_base;

@@ -168,6 +172,26 @@ meta_backend_x11_translate_device_event (MetaBackendX11 *x11,

   backend_x11_class->translate_device_event (x11, device_event);

 }

+static void

+maybe_translate_touch_replay_pointer_event (MetaBackendX11 *x11,

+                                            XIDeviceEvent  *device_event)

+{

+  MetaBackendX11Private *priv = meta_backend_x11_get_instance_private (x11);

+

+  if (!device_event->send_event &&

+      device_event->time != CurrentTime &&

+      priv->current_touch_replay_sync_serial !=

+      priv->pending_touch_replay_sync_serial &&

+      XSERVER_TIME_IS_BEFORE (device_event->time, priv->latest_evtime))

+    {

+      /* Emulated pointer events received after XIRejectTouch is received

+       * on a passive touch grab will contain older timestamps, update those

+       * so we dont get InvalidTime at grabs.

+       */

+      device_event->time = priv->latest_evtime;

+    }

+}

+

 static void

 translate_device_event (MetaBackendX11 *x11,

                         XIDeviceEvent  *device_event)

@@ -177,19 +201,7 @@ translate_device_event (MetaBackendX11 *x11,

   meta_backend_x11_translate_device_event (x11, device_event);

   if (!device_event->send_event && device_event->time != CurrentTime)

-    {

-      if (XSERVER_TIME_IS_BEFORE (device_event->time, priv->latest_evtime))

-        {

-          /* Emulated pointer events received after XIRejectTouch is received

-           * on a passive touch grab will contain older timestamps, update those

-           * so we dont get InvalidTime at grabs.

-           */

-          device_event->time = priv->latest_evtime;

-        }

-

-      /* Update the internal latest evtime, for any possible later use */

-      priv->latest_evtime = device_event->time;

-    }

+    priv->latest_evtime = device_event->time;

 }

 static void

@@ -254,6 +266,9 @@ maybe_spoof_event_as_stage_event (MetaBackendX11 *x11,

     case XI_Motion:

     case XI_ButtonPress:

     case XI_ButtonRelease:

+      maybe_translate_touch_replay_pointer_event (x11,

+                                                  (XIDeviceEvent *) input_event);

+      /* Intentional fall-through */

     case XI_KeyPress:

     case XI_KeyRelease:

     case XI_TouchBegin:

@@ -321,6 +336,17 @@ handle_host_xevent (MetaBackend *backend,

   MetaBackendX11Private *priv = meta_backend_x11_get_instance_private (x11);

   gboolean bypass_clutter = FALSE;

+  switch (event->type)

+    {

+    case ClientMessage:

+      if (event->xclient.window == meta_backend_x11_get_xwindow (x11) &&

+          event->xclient.message_type == priv->touch_replay_sync_atom)

+        priv->current_touch_replay_sync_serial = event->xclient.data.l[0];

+      break;

+    default:

+      break;

+    }

+

   XGetEventData (priv->xdisplay, &event->xcookie);

   {

@@ -528,6 +554,10 @@ meta_backend_x11_post_init (MetaBackend *backend)

   monitor_manager = meta_backend_get_monitor_manager (backend);

   g_signal_connect (monitor_manager, "monitors-changed-internal",

                     G_CALLBACK (on_monitors_changed), backend);

+

+  priv->touch_replay_sync_atom = XInternAtom (priv->xdisplay,

+                                              "_MUTTER_TOUCH_SEQUENCE_SYNC",

+                                              False);

 }

 static ClutterBackend *

@@ -603,6 +633,21 @@ meta_backend_x11_finish_touch_sequence (MetaBackend          *backend,

                       META_VIRTUAL_CORE_POINTER_ID,

                       clutter_x11_event_sequence_get_touch_detail (sequence),

                       DefaultRootWindow (priv->xdisplay), event_mode);

+

+  if (state == META_SEQUENCE_REJECTED)

+    {

+      XClientMessageEvent ev;

+

+      ev = (XClientMessageEvent) {

+          .type = ClientMessage,

+            .window = meta_backend_x11_get_xwindow (x11),

+            .message_type = priv->touch_replay_sync_atom,

+            .format = 32,

+            .data.l[0] = ++priv->pending_touch_replay_sync_serial,

+      };

+      XSendEvent (priv->xdisplay, meta_backend_x11_get_xwindow (x11),

+                  False, 0, (XEvent *) &ev;;

+    }

 }

 static void

-- 

2.23.0