fix(ui): re-organize tty fd handling and fix issues

- Use the correct fd to replace stdin on windows (CONIN)
- Don't start the TUI if there are no tty fd (not a regression,
  but makes sense regardless)
- De-mythologize "global input fd". it is just STDIN.

3 files changed, 7 insertions, 17 deletions

diff --git a/src/nvim/os/input.c b/src/nvim/os/input.c
index 5d2ac1e102..51cabfbcbf 100644
--- a/src/nvim/os/input.c
+++ b/src/nvim/os/input.c
@@ -44,7 +44,6 @@ typedef enum {
 static Stream read_stream = { .closed = true };  // Input before UI starts.
 static RBuffer *input_buffer = NULL;
 static bool input_eof = false;
-static int global_fd = -1;
 static bool blocking = false;
 static int cursorhold_time = 0;  ///< time waiting for CursorHold event
 static int cursorhold_tb_change_cnt = 0;  ///< tb_change_cnt when waiting started
@@ -58,25 +57,14 @@ void input_init(void)
   input_buffer = rbuffer_new(INPUT_BUFFER_SIZE + MAX_KEY_CODE_LEN);
 }
 
-void input_global_fd_init(int fd)
-{
-  global_fd = fd;
-}
-
-/// Global TTY (or pipe for "-es") input stream, before UI starts.
-int input_global_fd(void)
-{
-  return global_fd;
-}
-
-void input_start(int fd)
+void input_start(void)
 {
   if (!read_stream.closed) {
     return;
   }
 
-  input_global_fd_init(fd);
-  rstream_init_fd(&main_loop, &read_stream, fd, READ_BUFFER_SIZE);
+  used_stdin = true;
+  rstream_init_fd(&main_loop, &read_stream, STDIN_FILENO, READ_BUFFER_SIZE);
   rstream_start(&read_stream, input_read_cb, NULL);
 }
 
diff --git a/src/nvim/os/input.h b/src/nvim/os/input.h
index 7026781407..6f25efdc7b 100644
--- a/src/nvim/os/input.h
+++ b/src/nvim/os/input.h
@@ -7,6 +7,8 @@
 #include "nvim/api/private/defs.h"
 #include "nvim/event/multiqueue.h"
 
+EXTERN bool used_stdin INIT(= false);
+
 #ifdef INCLUDE_GENERATED_DECLARATIONS
 # include "os/input.h.generated.h"
 #endif
diff --git a/src/nvim/os/os_win_console.c b/src/nvim/os/os_win_console.c
index ec0f03a1dc..18f6e8b37b 100644
--- a/src/nvim/os/os_win_console.c
+++ b/src/nvim/os/os_win_console.c
@@ -14,7 +14,7 @@ static HWND hWnd = NULL;
 static HICON hOrigIconSmall = NULL;
 static HICON hOrigIcon = NULL;
 
-int os_get_conin_fd(void)
+int os_open_conin_fd(void)
 {
   const HANDLE conin_handle = CreateFile("CONIN$",
                                          GENERIC_READ | GENERIC_WRITE,
@@ -30,7 +30,7 @@ int os_get_conin_fd(void)
 void os_replace_stdin_to_conin(void)
 {
   close(STDIN_FILENO);
-  const int conin_fd = os_get_conin_fd();
+  const int conin_fd = os_open_conin_fd();
   assert(conin_fd == STDIN_FILENO);
 }