Send IPC modifier event on bar_modifier up/down

Detects when a bar modifier key is pressed/released and sends a modifier
IPC event to any listeners (usually swaybars).

This way a swaybar can listen on the modifier event and hide/show the
bar accordingly (not implemented yet)

The modifier event looks like this:

    {
      "change": "pressed", // or released
      "modifier": "Mod4"
    }

2 files changed, 7 insertions, 0 deletions

diff --git a/include/ipc-server.h b/include/ipc-server.h
index 04975093..47026bfd 100644
--- a/include/ipc-server.h
+++ b/include/ipc-server.h
@@ -15,6 +15,12 @@ void ipc_event_barconfig_update(struct bar_config *bar);
  * Send IPC mode event to all listening clients
  */
 void ipc_event_mode(const char *mode);
+/**
+ * Sends an IPC modifier event to all listening clients.  The modifier event
+ * includes a key 'change' with the value of state and a key 'modifier' with
+ * the name of that modifier.
+ */
+void ipc_event_modifier(uint32_t modifier, const char *state);
 const char *swayc_type_string(enum swayc_types type);
 
 #endif
diff --git a/include/ipc.h b/include/ipc.h
index e0b3b736..56593529 100644
--- a/include/ipc.h
+++ b/include/ipc.h
@@ -17,6 +17,7 @@ enum ipc_command_type {
         IPC_EVENT_WINDOW = (1 << 31 | 3),
         IPC_EVENT_BARCONFIG_UPDATE = (1 << 31 | 4),
         IPC_EVENT_BINDING = (1 << 31 | 5),
+        IPC_EVENT_MODIFIER = (1 << 31 | 6),
         IPC_SWAY_GET_PIXELS = 0x81
 };