tui: fix handling of bg response after suspend (#11145)

`tui_terminal_after_startup` gets called right after resuming from
suspending (via `Ctrl-z`) already (not delayed as with the startup
itself), and would set `waiting_for_bg_response` to false then directly.
This results in the terminal response not being processed then anymore,
and leaking into Neovim itself.

This changes it to try 5 times always, which means that it typically
would stop after a few characters of input from the user typically, e.g.
with tmux, which does not send a reply.

While it might be better to have something based on the time (e.g. only
wait for max 1s), this appears to be easier to do.

Fixes regression in 8a4ae3d.

3 files changed, 9 insertions, 10 deletions

diff --git a/src/nvim/tui/input.c b/src/nvim/tui/input.c
index 876f00e03e..844bc0db40 100644
--- a/src/nvim/tui/input.c
+++ b/src/nvim/tui/input.c
@@ -27,7 +27,7 @@ void tinput_init(TermInput *input, Loop *loop)
   input->loop = loop;
   input->paste = 0;
   input->in_fd = 0;
-  input->waiting_for_bg_response = false;
+  input->waiting_for_bg_response = 0;
   input->key_buffer = rbuffer_new(KEY_BUFFER_SIZE);
   uv_mutex_init(&input->key_buffer_mutex);
   uv_cond_init(&input->key_buffer_cond);
@@ -444,7 +444,7 @@ static void set_bg_deferred(void **argv)
 // [1] https://en.wikipedia.org/wiki/Luma_%28video%29
 static bool handle_background_color(TermInput *input)
 {
-  if (!input->waiting_for_bg_response) {
+  if (input->waiting_for_bg_response <= 0) {
     return false;
   }
   size_t count = 0;
@@ -465,9 +465,13 @@ static bool handle_background_color(TermInput *input)
     header_size = 10;
     num_components = 4;
   } else {
+    input->waiting_for_bg_response--;
+    if (input->waiting_for_bg_response == 0) {
+      DLOG("did not get a response for terminal background query");
+    }
     return false;
   }
-  input->waiting_for_bg_response = false;
+  input->waiting_for_bg_response = 0;
   rbuffer_consumed(input->read_stream.buffer, header_size);
   RBUFFER_EACH(input->read_stream.buffer, c, i) {
     count = i + 1;
diff --git a/src/nvim/tui/input.h b/src/nvim/tui/input.h
index 49ae32f00e..77bd6fa132 100644
--- a/src/nvim/tui/input.h
+++ b/src/nvim/tui/input.h
@@ -12,7 +12,7 @@ typedef struct term_input {
   // Phases: -1=all 0=disabled 1=first-chunk 2=continue 3=last-chunk
   int8_t paste;
   bool waiting;
-  bool waiting_for_bg_response;
+  int8_t waiting_for_bg_response;
   TermKey *tk;
 #if TERMKEY_VERSION_MAJOR > 0 || TERMKEY_VERSION_MINOR > 18
   TermKey_Terminfo_Getstr_Hook *tk_ti_hook_fn;  ///< libtermkey terminfo hook
diff --git a/src/nvim/tui/tui.c b/src/nvim/tui/tui.c
index 956d4eb9da..150862bb18 100644
--- a/src/nvim/tui/tui.c
+++ b/src/nvim/tui/tui.c
@@ -296,7 +296,7 @@ static void terminfo_start(UI *ui)
   unibi_out(ui, unibi_keypad_xmit);
   unibi_out(ui, unibi_clear_screen);
   // Ask the terminal to send us the background color.
-  data->input.waiting_for_bg_response = true;
+  data->input.waiting_for_bg_response = 5;
   unibi_out_ext(ui, data->unibi_ext.get_bg);
   // Enable bracketed paste
   unibi_out_ext(ui, data->unibi_ext.enable_bracketed_paste);
@@ -366,11 +366,6 @@ static void tui_terminal_after_startup(UI *ui)
   // 2.3 bug(?) which caused slow drawing during startup.  #7649
   unibi_out_ext(ui, data->unibi_ext.enable_focus_reporting);
   flush_buf(ui);
-
-  if (data->input.waiting_for_bg_response) {
-    DLOG("did not get a response for terminal background query");
-    data->input.waiting_for_bg_response = false;
-  }
 }
 
 static void tui_terminal_stop(UI *ui)