Make process_text() optional

Not all key processors support text injection (HID keyboard does not
support it).

Instead of providing a dummy op function, set it to NULL and check on
the caller side before calling it.

app/src/hid_keyboard.c

@@ -387,15 +387,6 @@ sc_key_processor_process_key(struct sc_key_processor *kp,
     }
 }
 
-static void
-sc_key_processor_process_text(struct sc_key_processor *kp,
-                              const struct sc_text_event *event) {
-    (void) kp;
-    (void) event;
-
-    // Never forward text input via HID (all the keys are injected separately)
-}
-
 bool
 sc_hid_keyboard_init(struct sc_hid_keyboard *kb, struct sc_aoa *aoa) {
     kb->aoa = aoa;
@@ -415,7 +406,9 @@ sc_hid_keyboard_init(struct sc_hid_keyboard *kb, struct sc_aoa *aoa) {
 
     static const struct sc_key_processor_ops ops = {
         .process_key = sc_key_processor_process_key,
-        .process_text = sc_key_processor_process_text,
+        // Never forward text input via HID (all the keys are injected
+        // separately)
+        .process_text = NULL,
     };
 
     // Clipboard synchronization is requested over the control socket, while HID

app/src/input_manager.c

@@ -384,6 +384,11 @@ rotate_client_right(struct screen *screen) {
 static void
 input_manager_process_text_input(struct input_manager *im,
                                  const SDL_TextInputEvent *event) {
+    if (!im->kp->ops->process_text) {
+        // The key processor does not support text input
+        return;
+    }
+
     if (is_shortcut_mod(im, SDL_GetModState())) {
         // A shortcut must never generate text events
         return;
@@ -620,6 +625,7 @@ input_manager_process_key(struct input_manager *im,
         .mods_state = sc_mods_state_from_sdl(event->keysym.mod),
     };
 
+    assert(im->kp->ops->process_key);
     im->kp->ops->process_key(im->kp, &evt, ack_to_wait);
 }
 

app/src/trait/key_processor.h

@@ -29,17 +29,24 @@ struct sc_key_processor {
 struct sc_key_processor_ops {
 
     /**
-     * Process the keyboard event
+     * Process a keyboard event
      *
      * The `sequence` number (if different from `SC_SEQUENCE_INVALID`) indicates
      * the acknowledgement number to wait for before injecting this event.
      * This allows to ensure that the device clipboard is set before injecting
      * Ctrl+v on the device.
+     *
+     * This function is mandatory.
      */
     void
     (*process_key)(struct sc_key_processor *kp,
                    const struct sc_key_event *event, uint64_t ack_to_wait);
 
+    /**
+     * Process an input text
+     *
+     * This function is optional.
+     */
     void
     (*process_text)(struct sc_key_processor *kp,
                     const struct sc_text_event *event);