input method: avoid sending IM sent keys to grabs.

IM sends release key events when deactivated, which caused e.g. the
switcher plugin to deactivate early. The plugin has a higher priority
when activating, but lower for subsequent key events.

src/core/seat/keyboard.cpp

@@ -61,7 +61,8 @@ void wf::keyboard_t::setup_listeners()
                 }
             }
 
-            if (seat->priv->keyboard_focus)
+            // don't send IM sent keys to plugin grabs
+            if (seat->priv->keyboard_focus && !(seat->priv->is_grab && is_im_sent))
             {
                 seat->priv->keyboard_focus->keyboard_interaction()
                     .handle_keyboard_key(wf::get_core().seat.get(), *ev);

src/core/seat/seat-impl.hpp

@@ -57,6 +57,7 @@ struct seat_t::impl
 
     void set_keyboard_focus(wf::scene::node_ptr keyboard_focus);
     wf::scene::node_ptr keyboard_focus;
+    bool is_grab = false;
     // Keys sent to the current keyboard focus
     std::multiset<uint32_t> pressed_keys;
     void transfer_grab(wf::scene::node_ptr new_focus);

src/core/seat/seat.cpp

@@ -500,6 +500,7 @@ void wf::seat_t::impl::transfer_grab(wf::scene::node_ptr grab_node)
     }
 
     this->keyboard_focus = grab_node;
+    this->is_grab = true;
     grab_node->keyboard_interaction().handle_keyboard_enter(wf::get_core().seat.get());
 
     wf::keyboard_focus_changed_signal data;
@@ -521,6 +522,7 @@ void wf::seat_t::impl::set_keyboard_focus(wf::scene::node_ptr new_focus)
     }
 
     this->keyboard_focus = new_focus;
+    this->is_grab = false;
     if (new_focus)
     {
         new_focus->keyboard_interaction().handle_keyboard_enter(wf::get_core().seat.get());