klib: Improve klist.h

- Add `kl_shift_at` macro and backing function. This can be used to shift
  elements at arbitrary positions. `kl_shift` is now defined on top of the new
  macro.
- Change shift/push API, now `kl_push` accepts an object as parameter and
  `kl_shift` returns the object instead of a status. An assertion against
  shifting at the end of a list(or empty lists) was added.
- Add `kl_iter` and `kl_iter_at` macros. `kl_iter_at` is for starting the
  iteration at arbitrary positions.

1 files changed, 3 insertions, 4 deletions

diff --git a/src/nvim/os/event.c b/src/nvim/os/event.c
index 4c3a4581c3..56874b495d 100644
--- a/src/nvim/os/event.c
+++ b/src/nvim/os/event.c
@@ -149,7 +149,7 @@ void event_push(Event event, bool deferred)
   // returns(user hits a key for example). To avoid this scenario, we call
   // uv_stop when a event is enqueued.
   uv_stop(uv_default_loop());
-  *kl_pushp(Event, deferred ? deferred_events : immediate_events) = event;
+  kl_push(Event, deferred ? deferred_events : immediate_events, event);
 }
 
 void event_process(void)
@@ -159,9 +159,8 @@ void event_process(void)
 
 static void process_events_from(klist_t(Event) *queue)
 {
-  Event event;
-
-  while (kl_shift(Event, queue, &event) == 0) {
+  while (!kl_empty(queue)) {
+    Event event = kl_shift(Event, queue);
     event.handler(event);
   }
 }