api: nvim_get_mode()

Asynchronous API functions are served immediately, which means pending
input could change the state of Nvim shortly after an async API function
result is returned.

nvim_get_mode() is different:
  - If RPCs are known to be blocked, it responds immediately (without
    flushing the input/event queue)
  - else it is handled just-in-time before waiting for input, after
    pending input was processed. This makes the result more reliable
    (but not perfect).

Internally this is handled as a special case, but _semantically_ nothing
has changed: API users never know when input flushes, so this internal
special-case doesn't violate that. As far as API users are concerned,
nvim_get_mode() is just another asynchronous API function.

In all cases nvim_get_mode() never blocks for more than the time it
takes to flush the input/event queue (~µs).

Note: This doesn't address #6166; nvim_get_mode() will provoke #6166 if
e.g. `d` is operator-pending.

Closes #6159

1 files changed, 0 insertions, 3 deletions

diff --git a/src/nvim/tui/tui.c b/src/nvim/tui/tui.c
index 21abc19c47..356221f7ce 100644
--- a/src/nvim/tui/tui.c
+++ b/src/nvim/tui/tui.c
@@ -74,9 +74,6 @@ typedef struct {
   bool out_isatty;
   SignalWatcher winch_handle, cont_handle;
   bool cont_received;
-  // Event scheduled by the ui bridge. Since the main thread suspends until
-  // the event is handled, it is fine to use a single field instead of a queue
-  Event scheduled_event;
   UGrid grid;
   kvec_t(Rect) invalid_regions;
   int out_fd;