feat(ui): UI :detach command

Problem:
Cannot detach the current UI.

Solution:
- Introduce `:detach`.
- Introduce `Channel.detach`.

Co-authored-by: bfredl <bjorn.linse@gmail.com>

2 files changed, 6 insertions, 3 deletions

diff --git a/src/nvim/api/ui.c b/src/nvim/api/ui.c
index f6f32a73ed..41a09999d0 100644
--- a/src/nvim/api/ui.c
+++ b/src/nvim/api/ui.c
@@ -189,6 +189,7 @@ void nvim_ui_attach(uint64_t channel_id, Integer width, Integer height, Dict opt
   ui->wildmenu_active = false;
 
   pmap_put(uint64_t)(&connected_uis, channel_id, ui);
+  current_ui = channel_id;
   ui_attach_impl(ui, channel_id);
 
   may_trigger_vim_suspend_resume(false);
@@ -214,6 +215,7 @@ void nvim_ui_set_focus(uint64_t channel_id, Boolean gained, Error *error)
   }
 
   if (gained) {
+    current_ui = channel_id;
     may_trigger_vim_suspend_resume(false);
   }
 
diff --git a/src/nvim/api/vim.c b/src/nvim/api/vim.c
index c103a56032..02aa73d98d 100644
--- a/src/nvim/api/vim.c
+++ b/src/nvim/api/vim.c
@@ -359,11 +359,11 @@ void nvim_feedkeys(String keys, String mode, Boolean escape_ks)
 /// @param keys to be typed
 /// @return Number of bytes actually written (can be fewer than
 ///         requested if the buffer becomes full).
-Integer nvim_input(String keys)
+Integer nvim_input(uint64_t channel_id, String keys)
   FUNC_API_SINCE(1) FUNC_API_FAST
 {
   may_trigger_vim_suspend_resume(false);
-  return (Integer)input_enqueue(keys);
+  return (Integer)input_enqueue(channel_id, keys);
 }
 
 /// Send mouse event from GUI.
@@ -1485,7 +1485,8 @@ Array nvim_get_api_info(uint64_t channel_id, Arena *arena)
   return rv;
 }
 
-/// Self-identifies the client. Sets the `client` object returned by |nvim_get_chan_info()|.
+/// Self-identifies the client, and sets optional flags on the channel. Defines the `client` object
+/// returned by |nvim_get_chan_info()|.
 ///
 /// Clients should call this just after connecting, to provide hints for debugging and
 /// orchestration. (Note: Something is better than nothing! Fields are optional, but at least set