frames: Keep information about the ongoing grab operation, and retry if needed.

When a passive touch grab is rejected over the frame, management is punted to
the frame itself, and pointer events emulated, but the attempt to transfer the
grab from the GDK connection to the Clutter one fails with AlreadyGrabbed, and
will fail until the Clutter connection receives the XI_TouchEnd resulting from
XIRejectTouch, gotten after the XI_ButtonPress on the GDK connection.

In order to bypass this shortcoming, store the current grab operation on the
frame as long as the button is pressed, so it is retried once on the next
motion event happening during frame dragging, that will have a recent enough
timestamp to succeed. If no grabbing succeeded, the current grab operation
data will be reset on GDK_BUTTON_RELEASE.

src/ui/frames.c

@@ -1136,6 +1136,64 @@ meta_frame_right_click_event(MetaUIFrame     *frame,
   return meta_frame_titlebar_event (frame, event, action);
 }
 
+static gboolean
+meta_frames_try_grab_op (MetaFrames  *frames,
+                         MetaUIFrame *frame,
+                         MetaGrabOp   op,
+                         gdouble      grab_x,
+                         gdouble      grab_y,
+                         guint32      time)
+{
+  Display *display;
+  gboolean ret;
+
+  display = GDK_DISPLAY_XDISPLAY (gdk_display_get_default ());
+  ret = meta_core_begin_grab_op (display,
+                                 frame->xwindow,
+                                 op,
+                                 FALSE,
+                                 TRUE,
+                                 frame->grab_button,
+                                 0,
+                                 time,
+                                 grab_x, grab_y);
+  if (!ret)
+    {
+      frames->current_grab_op = op;
+      frames->grab_frame = frame;
+      frames->grab_x = grab_x;
+      frames->grab_y = grab_y;
+    }
+
+  return ret;
+}
+
+static gboolean
+meta_frames_retry_grab_op (MetaFrames *frames,
+                           guint       time)
+{
+  Display *display;
+  MetaGrabOp op;
+
+  if (frames->current_grab_op == META_GRAB_OP_NONE)
+    return TRUE;
+
+  op = frames->current_grab_op;
+  frames->current_grab_op = META_GRAB_OP_NONE;
+  display = GDK_DISPLAY_XDISPLAY (gdk_display_get_default ());
+
+  return meta_core_begin_grab_op (display,
+                                  frames->grab_frame->xwindow,
+                                  op,
+                                  FALSE,
+                                  TRUE,
+                                  frames->grab_frame->grab_button,
+                                  0,
+                                  time,
+                                  frames->grab_x,
+                                  frames->grab_y);
+}
+
 static gboolean
 meta_frames_button_press_event (GtkWidget      *widget,
                                 GdkEventButton *event)
@@ -1190,6 +1248,8 @@ meta_frames_button_press_event (GtkWidget      *widget,
   if (meta_core_get_grab_op (display) != META_GRAB_OP_NONE)
     return FALSE; /* already up to something */
 
+  frame->grab_button = event->button;
+
   if (event->button == 1 &&
       (control == META_FRAME_CONTROL_MAXIMIZE ||
        control == META_FRAME_CONTROL_UNMAXIMIZE ||
@@ -1293,16 +1353,9 @@ meta_frames_button_press_event (GtkWidget      *widget,
           break;
         }
 
-      meta_core_begin_grab_op (display,
+      meta_frames_try_grab_op (frames, frame, op,
-                               frame->xwindow,
+                               event->x_root, event->y_root,
-                               op,
+                               event->time);
-                               TRUE,
-                               TRUE,
-                               event->button,
-                               0,
-                               event->time,
-                               event->x_root,
-                               event->y_root);
     }
   else if (control == META_FRAME_CONTROL_TITLE &&
            event->button == 1)
@@ -1315,16 +1368,10 @@ meta_frames_button_press_event (GtkWidget      *widget,
 
       if (flags & META_FRAME_ALLOWS_MOVE)
         {
-          meta_core_begin_grab_op (display,
+          meta_frames_try_grab_op (frames, frame,
-                                   frame->xwindow,
                                    META_GRAB_OP_MOVING,
-                                   TRUE,
+                                   event->x_root, event->y_root,
-                                   TRUE,
+                                   event->time);
-                                   event->button,
-                                   0,
-                                   event->time,
-                                   event->x_root,
-                                   event->y_root);
         }
     }
   else if (event->button == 2)
@@ -1349,6 +1396,7 @@ meta_frames_button_release_event    (GtkWidget           *widget,
 
   frames = META_FRAMES (widget);
   display = GDK_DISPLAY_XDISPLAY (gdk_display_get_default ());
+  frames->current_grab_op = META_GRAB_OP_NONE;
 
   frame = meta_frames_lookup_window (frames, GDK_WINDOW_XID (event->window));
   if (frame == NULL)
@@ -1560,6 +1608,10 @@ meta_frames_motion_notify_event     (GtkWidget           *widget,
       meta_frames_update_prelit_control (frames, frame, control);
     }
 
+  if ((event->state & GDK_BUTTON1_MASK) &&
+      frames->current_grab_op != META_GRAB_OP_NONE)
+    meta_frames_retry_grab_op (frames, event->time);
+
   return TRUE;
 }
 

src/ui/frames.h

@@ -100,6 +100,12 @@ struct _MetaFrames
   GtkStyleContext *normal_style;
   GHashTable *style_variants;
 
+  MetaGrabOp current_grab_op;
+  MetaUIFrame *grab_frame;
+  guint grab_button;
+  gdouble grab_x;
+  gdouble grab_y;
+
   Window grab_xwindow;
 };
 

src/ui/ui.c

@@ -205,6 +205,12 @@ maybe_redirect_mouse_event (XEvent *xevent)
       gevent = gdk_event_new (GDK_MOTION_NOTIFY);
       gevent->motion.type = GDK_MOTION_NOTIFY;
       gevent->motion.window = g_object_ref (gdk_window);
+      gevent->motion.time = xev_d->time;
+      gevent->motion.x_root = xev_d->root_x;
+      gevent->motion.y_root = xev_d->root_y;
+
+      if (XIMaskIsSet (xev_d->buttons.mask, 1))
+        gevent->motion.state |= GDK_BUTTON1_MASK;
       break;
     case XI_Enter:
     case XI_Leave: