rpc: allow handling of nvim_ui_try_resize at the pager

This makes external UI behave consistenly with TUI w.r.t resizes.
Which will be needed anyway as TUI will use the external UI protocol
soon.

2 files changed, 48 insertions, 2 deletions

diff --git a/src/nvim/event/multiqueue.c b/src/nvim/event/multiqueue.c
index ef9f3f1870..a1b75f66a5 100644
--- a/src/nvim/event/multiqueue.c
+++ b/src/nvim/event/multiqueue.c
@@ -78,6 +78,13 @@ struct multiqueue {
   size_t size;
 };
 
+typedef struct {
+  Event event;
+  bool fired;
+  int refcount;
+} SplitEvent;
+
+
 #ifdef INCLUDE_GENERATED_DECLARATIONS
 # include "event/multiqueue.c.generated.h"
 #endif
@@ -245,3 +252,33 @@ static MultiQueueItem *multiqueue_node_data(QUEUE *q)
 {
   return QUEUE_DATA(q, MultiQueueItem, node);
 }
+
+/// Allow an event to be processed by multiple child queues to the main queue
+///
+/// The handler will be fired once by the _first_ queue that processes the
+/// event. Later processing will do nothing (just memory cleanup).
+///
+/// @param ev the event
+/// @param num number of queues that the split event will be put on
+/// @return an Event that is safe to put onto `num` queues
+Event event_split(Event ev, int num)
+{
+  SplitEvent *data = xmalloc(sizeof(*data));
+  data->event = ev;
+  data->fired = false;
+  data->refcount = num;
+  return event_create(split_event, 1, data);
+}
+static void split_event(void ** argv)
+{
+  SplitEvent *data = argv[0];
+  if (!data->fired) {
+    data->fired = true;
+    if (data->event.handler) {
+      data->event.handler(data->event.argv);
+    }
+  }
+  if ((--data->refcount) == 0) {
+    xfree(data);
+  }
+}
diff --git a/src/nvim/msgpack_rpc/channel.c b/src/nvim/msgpack_rpc/channel.c
index 81c9f1e3f4..19f626c63b 100644
--- a/src/nvim/msgpack_rpc/channel.c
+++ b/src/nvim/msgpack_rpc/channel.c
@@ -31,6 +31,7 @@
 #include "nvim/misc1.h"
 #include "nvim/lib/kvec.h"
 #include "nvim/os/input.h"
+#include "nvim/ui.h"
 
 #if MIN_LOG_LEVEL > DEBUG_LOG_LEVEL
 #define log_client_msg(...)
@@ -355,11 +356,19 @@ static void handle_request(Channel *channel, msgpack_object *request)
       request_event((void **)&evdata);
     }
   } else {
-    multiqueue_put(channel->events, request_event, 1, evdata);
-    DLOG("RPC: scheduled %.*s", method->via.bin.size, method->via.bin.ptr);
+    bool is_resize = handler.fn == handle_nvim_ui_try_resize;
+    if (is_resize) {
+      Event ev = event_split(event_create(request_event, 1, evdata), 2);
+      multiqueue_put_event(channel->events, ev);
+      multiqueue_put_event(resize_events, ev);
+    } else {
+      multiqueue_put(channel->events, request_event, 1, evdata);
+      DLOG("RPC: scheduled %.*s", method->via.bin.size, method->via.bin.ptr);
+    }
   }
 }
 
+
 /// Handles a message, depending on the type:
 ///   - Request: invokes method and writes the response (or error).
 ///   - Notification: invokes method (emits `nvim_error_event` on error).