[mutter/gnome-3-34] cursor-tracker: Add API to keep the wayland pointer focus while hidden

[Florian Müllner <fmuellner src gnome org>]

commit cbbffd1db741fa47499d82d2a86f5c6baa2908f4
Author: Jonas Dreßler <verdre v0yd nl>
Date:   Mon Oct 7 14:32:11 2019 +0200

    cursor-tracker: Add API to keep the wayland pointer focus while hidden
    
    Since commit a2a8f0cda we force the focus surface of the
    meta-wayland-pointer to NULL while the pointer is invisible. This
    introduced an issue with the a11y magnifier of the shell, which uses
    `meta_cursor_tracker_set_pointer_visible` to hide the real cursor and
    show its own magnified cursor at the correct position: Because the
    meta-wayland-pointer is still used to communicate with Wayland clients,
    the UI of the windows will not respond to mouse movement anymore as
    soon as the real cursor is hidden.
    
    Fix this issue for now by adding an additional method to the
    cursor-tracker which allows disabling the behavior commit a2a8f0cda
    introduced.
    
    https://gitlab.gnome.org/GNOME/mutter/merge_requests/832

 src/backends/meta-cursor-tracker-private.h |  1 +
 src/backends/meta-cursor-tracker.c         | 39 ++++++++++++++++++++++++++++++
 src/meta/meta-cursor-tracker.h             |  7 ++++++
 src/wayland/meta-wayland-pointer.c         |  9 ++++---
 4 files changed, 53 insertions(+), 3 deletions(-)
---
diff --git a/src/backends/meta-cursor-tracker-private.h b/src/backends/meta-cursor-tracker-private.h
index 29ee94044..0923337fb 100644
--- a/src/backends/meta-cursor-tracker-private.h
+++ b/src/backends/meta-cursor-tracker-private.h
@@ -31,6 +31,7 @@ struct _MetaCursorTracker {
   GObject parent_instance;
 
   gboolean is_showing;
+  gboolean keep_focus_while_hidden;
 
   MetaCursorSprite *effective_cursor; /* May be NULL when hidden */
   MetaCursorSprite *displayed_cursor;
diff --git a/src/backends/meta-cursor-tracker.c b/src/backends/meta-cursor-tracker.c
index 45291e286..346e3faae 100644
--- a/src/backends/meta-cursor-tracker.c
+++ b/src/backends/meta-cursor-tracker.c
@@ -136,6 +136,7 @@ static void
 meta_cursor_tracker_init (MetaCursorTracker *self)
 {
   self->is_showing = TRUE;
+  self->keep_focus_while_hidden = FALSE;
 }
 
 static void
@@ -457,6 +458,44 @@ meta_cursor_tracker_set_pointer_visible (MetaCursorTracker *tracker,
   g_signal_emit (tracker, signals[VISIBILITY_CHANGED], 0);
 }
 
+/**
+ * meta_cursor_tracker_get_keep_focus_while_hidden:
+ * @tracker: a #MetaCursorTracker object.
+ *
+ * Returns: %FALSE if the Wayland focus surface of the pointer will
+ * be forced to NULL while the pointer is hidden, %TRUE otherwise.
+ * This function is only meant to be used by the magnifier of the shell
+ * and will be removed in a future release.
+ */
+gboolean
+meta_cursor_tracker_get_keep_focus_while_hidden (MetaCursorTracker *tracker)
+{
+  return tracker->keep_focus_while_hidden;
+}
+
+/**
+ * meta_cursor_tracker_set_keep_focus_while_hidden:
+ * @tracker: a #MetaCursorTracker object.
+ * @keep_focus: whether to keep the cursor focus while hidden
+ *
+ * If this is set to %TRUE, the Wayland focus surface of the pointer will
+ * not be forced to NULL while the pointer is hidden.
+ * This function is only meant to be used by the magnifier of the shell
+ * and will be removed in a future release.
+ */
+void
+meta_cursor_tracker_set_keep_focus_while_hidden (MetaCursorTracker *tracker,
+                                                 gboolean           keep_focus)
+{
+  if (keep_focus == tracker->keep_focus_while_hidden)
+    return;
+  tracker->keep_focus_while_hidden = keep_focus;
+
+  sync_cursor (tracker);
+
+  g_signal_emit (tracker, signals[VISIBILITY_CHANGED], 0);
+}
+
 MetaCursorSprite *
 meta_cursor_tracker_get_displayed_cursor (MetaCursorTracker *tracker)
 {
diff --git a/src/meta/meta-cursor-tracker.h b/src/meta/meta-cursor-tracker.h
index 2f51115e4..6aef2745d 100644
--- a/src/meta/meta-cursor-tracker.h
+++ b/src/meta/meta-cursor-tracker.h
@@ -62,4 +62,11 @@ META_EXPORT
 void           meta_cursor_tracker_set_pointer_visible (MetaCursorTracker *tracker,
                                                         gboolean           visible);
 
+META_EXPORT
+gboolean       meta_cursor_tracker_get_keep_focus_while_hidden (MetaCursorTracker *tracker);
+
+META_EXPORT
+void           meta_cursor_tracker_set_keep_focus_while_hidden (MetaCursorTracker *tracker,
+                                                                gboolean           keep_focus);
+
 #endif
diff --git a/src/wayland/meta-wayland-pointer.c b/src/wayland/meta-wayland-pointer.c
index 751f6b9b9..b69f43ab3 100644
--- a/src/wayland/meta-wayland-pointer.c
+++ b/src/wayland/meta-wayland-pointer.c
@@ -228,7 +228,8 @@ sync_focus_surface (MetaWaylandPointer *pointer)
   MetaBackend *backend = meta_get_backend ();
   MetaCursorTracker *cursor_tracker = meta_backend_get_cursor_tracker (backend);
 
-  if (!meta_cursor_tracker_get_pointer_visible (cursor_tracker))
+  if (!meta_cursor_tracker_get_pointer_visible (cursor_tracker) &&
+      !meta_cursor_tracker_get_keep_focus_while_hidden (cursor_tracker))
     {
       meta_wayland_pointer_set_focus (pointer, NULL);
       return;
@@ -433,7 +434,8 @@ default_grab_focus (MetaWaylandPointerGrab *grab,
   if (!meta_wayland_seat_has_pointer (seat))
     return;
 
-  if (!meta_cursor_tracker_get_pointer_visible (cursor_tracker))
+  if (!meta_cursor_tracker_get_pointer_visible (cursor_tracker) &&
+      !meta_cursor_tracker_get_keep_focus_while_hidden (cursor_tracker))
     return;
 
   if (pointer->button_count > 0)
@@ -898,7 +900,8 @@ meta_wayland_pointer_set_focus (MetaWaylandPointer *pointer,
   MetaCursorTracker *cursor_tracker = meta_backend_get_cursor_tracker (backend);
 
   g_return_if_fail (meta_cursor_tracker_get_pointer_visible (cursor_tracker) ||
-                   surface == NULL);
+                    meta_cursor_tracker_get_keep_focus_while_hidden (cursor_tracker) ||
+                    surface == NULL);
 
   if (pointer->focus_surface == surface)
     return;