[PATCH xserver 2/4 v5] xwayland: add a server sync before repeating keys

[Olivier Fourdan]

Key repeat is handled by the X server, but input events need to be
processed and forwarded by the Wayland compositor first.

Make sure the Wayland compositor is actually processing events, to
avoid repeating keys in Xwayland while the Wayland compositor cannot
deal with input events for whatever reason, thus not dispatching key
release events, leading to repeated keys while the user has already
released the key.

Bugzilla: https://bugzilla.gnome.org/show_bug.cgi?id=762618
Signed-off-by: Olivier Fourdan <ofourdan at redhat.com>
---
 v2: A slightly less hack-y-ish version of the patch
     Use xwl_seat to store the pending sync, set up callback fpr keyboard
     in seat_handle_capabilities() and add a call to _dispatch_pending()
     in the callback function to make sure we didn't miss a reply
 v3: Small clean-up,
     Remove the call to wl_display_dispatch_pending() that we added
     in v2 as we shall do it in two other separate patches to follow.
 v4: Use a list to store the devices pending a compositor sync per
     xwl_seat, add the check repeat handler to xwl_seat->keyboard as
     well, as per Daniel's last review.
 v5: Remove device from pending sync on keyboard removal as well, to be
     on the safe side.

 hw/xwayland/xwayland-input.c | 74 +++++++++++++++++++++++++++++++++++++++++++-
 hw/xwayland/xwayland.h       |  2 ++
 2 files changed, 75 insertions(+), 1 deletion(-)

diff --git a/hw/xwayland/xwayland-input.c b/hw/xwayland/xwayland-input.c
index cbc1bf2..5c979f5 100644
--- a/hw/xwayland/xwayland-input.c
+++ b/hw/xwayland/xwayland-input.c
@@ -41,6 +41,11 @@
         (miPointerPtr)dixLookupPrivate(&(dev)->devPrivates, miPointerPrivKey): \
         (miPointerPtr)dixLookupPrivate(&(GetMaster(dev, MASTER_POINTER))->devPrivates, miPointerPrivKey))
 
+struct sync_pending {
+    struct xorg_list l;
+    DeviceIntPtr pending_dev;
+};
+
 static void
 xwl_pointer_control(DeviceIntPtr device, PtrCtrl *ctrl)
 {
@@ -527,6 +532,59 @@ keyboard_handle_modifiers(void *data, struct wl_keyboard *keyboard,
 }
 
 static void
+remove_sync_pending(DeviceIntPtr dev)
+{
+    struct xwl_seat *xwl_seat = dev->public.devicePrivate;
+    struct sync_pending *p, *npd;
+
+    xorg_list_for_each_entry_safe(p, npd, &xwl_seat->sync_pending, l)
+        if (p->pending_dev == dev) {
+            xorg_list_del(&xwl_seat->sync_pending);
+            free (p);
+            return;
+        }
+}
+
+static void
+sync_callback(void *data, struct wl_callback *callback, uint32_t serial)
+{
+    DeviceIntPtr dev = (DeviceIntPtr) data;
+
+    remove_sync_pending(dev);
+    wl_callback_destroy(callback);
+}
+
+static const struct wl_callback_listener sync_listener = {
+   sync_callback
+};
+
+static Bool
+keyboard_check_repeat (DeviceIntPtr dev, XkbSrvInfoPtr xkbi, unsigned key)
+{
+    struct xwl_seat *xwl_seat = dev->public.devicePrivate;
+    struct xwl_screen *xwl_screen = xwl_seat->xwl_screen;
+    struct wl_callback *callback;
+    struct sync_pending *p;
+
+    xorg_list_for_each_entry(p, &xwl_seat->sync_pending, l)
+        if (p->pending_dev == dev) {
+            ErrorF("Key repeat discarded, Wayland compositor doesn't "
+                   "seem to be processing events fast enough!\n");
+
+            return FALSE;
+        }
+
+    p = xnfalloc(sizeof(struct sync_pending));
+    p->pending_dev = dev;
+    callback = wl_display_sync (xwl_screen->display);
+    xorg_list_add(&p->l, &xwl_seat->sync_pending);
+
+    wl_callback_add_listener(callback, &sync_listener, dev);
+
+    return TRUE;
+}
+
+static void
 keyboard_handle_repeat_info (void *data, struct wl_keyboard *keyboard,
                              int32_t rate, int32_t delay)
 {
@@ -716,6 +774,7 @@ seat_handle_capabilities(void *data, struct wl_seat *seat,
                          enum wl_seat_capability caps)
 {
     struct xwl_seat *xwl_seat = data;
+    DeviceIntPtr master;
 
     if (caps & WL_SEAT_CAPABILITY_POINTER && xwl_seat->wl_pointer == NULL) {
         xwl_seat->wl_pointer = wl_seat_get_pointer(seat);
@@ -748,12 +807,18 @@ seat_handle_capabilities(void *data, struct wl_seat *seat,
             ActivateDevice(xwl_seat->keyboard, TRUE);
         }
         EnableDevice(xwl_seat->keyboard, TRUE);
+        xwl_seat->keyboard->key->xkbInfo->checkRepeat = keyboard_check_repeat;
+        master = GetMaster(xwl_seat->keyboard, MASTER_KEYBOARD);
+        if (master)
+            master->key->xkbInfo->checkRepeat = keyboard_check_repeat;
     } else if (!(caps & WL_SEAT_CAPABILITY_KEYBOARD) && xwl_seat->wl_keyboard) {
         wl_keyboard_release(xwl_seat->wl_keyboard);
         xwl_seat->wl_keyboard = NULL;
 
-        if (xwl_seat->keyboard)
+        if (xwl_seat->keyboard) {
+            remove_sync_pending(xwl_seat->keyboard);
             DisableDevice(xwl_seat->keyboard, TRUE);
+        }
     }
 
     if (caps & WL_SEAT_CAPABILITY_TOUCH && xwl_seat->wl_touch == NULL) {
@@ -814,12 +879,14 @@ create_input_device(struct xwl_screen *xwl_screen, uint32_t id, uint32_t version
     wl_array_init(&xwl_seat->keys);
 
     xorg_list_init(&xwl_seat->touches);
+    xorg_list_init(&xwl_seat->sync_pending);
 }
 
 void
 xwl_seat_destroy(struct xwl_seat *xwl_seat)
 {
     struct xwl_touch *xwl_touch, *next_xwl_touch;
+    struct sync_pending *p, *npd;
 
     xorg_list_for_each_entry_safe(xwl_touch, next_xwl_touch,
                                   &xwl_seat->touches, link_touch) {
@@ -827,6 +894,11 @@ xwl_seat_destroy(struct xwl_seat *xwl_seat)
         free(xwl_touch);
     }
 
+    xorg_list_for_each_entry_safe(p, npd, &xwl_seat->sync_pending, l) {
+        xorg_list_del(&xwl_seat->sync_pending);
+        free (p);
+    }
+
     wl_seat_destroy(xwl_seat->seat);
     wl_surface_destroy(xwl_seat->cursor);
     if (xwl_seat->cursor_frame_cb)
diff --git a/hw/xwayland/xwayland.h b/hw/xwayland/xwayland.h
index 67b30cb..5c053d9 100644
--- a/hw/xwayland/xwayland.h
+++ b/hw/xwayland/xwayland.h
@@ -138,6 +138,8 @@ struct xwl_seat {
     size_t keymap_size;
     char *keymap;
     struct wl_surface *keyboard_focus;
+
+    struct xorg_list sync_pending;
 };
 
 struct xwl_output {
-- 
2.7.4