added w_last_used to struct window_S

runtime/lua/vim/_meta/builtin_types.lua

@@ -60,6 +60,7 @@
 --- @field winid integer
 --- @field winnr integer
 --- @field winrow integer
+--- @field lastused integer
 
 --- @class vim.fn.sign_define.dict
 --- @field text string

src/nvim/buffer_defs.h

@@ -1328,4 +1328,6 @@ struct window_S {
   StlClickDefinition *w_statuscol_click_defs;
   // Size of the w_statuscol_click_defs array
   size_t w_statuscol_click_defs_size;
+
+  time_t w_last_used;  // time when the window was last used
 };

src/nvim/eval/window.c

@@ -332,6 +332,7 @@ static dict_T *get_win_info(win_T *wp, int16_t tpnr, int16_t winnr)
   tv_dict_add_nr(dict, S_LEN("textoff"), win_col_off(wp));
   tv_dict_add_nr(dict, S_LEN("terminal"), bt_terminal(wp->w_buffer));
   tv_dict_add_nr(dict, S_LEN("quickfix"), bt_quickfix(wp->w_buffer));
+  tv_dict_add_nr(dict, S_LEN("lastused"), wp->w_last_used);
   tv_dict_add_nr(dict, S_LEN("loclist"),
                  (bt_quickfix(wp->w_buffer) && wp->w_llist_ref != NULL));
 

src/nvim/window.c

@@ -2435,6 +2435,8 @@ void leaving_window(win_T *const win)
 void entering_window(win_T *const win)
   FUNC_ATTR_NONNULL_ALL
 {
+  win->w_last_used = time(NULL);
+
   // Only matters for a prompt window.
   if (!bt_prompt(win->w_buffer)) {
     return;
@@ -2468,6 +2470,7 @@ void win_init_empty(win_T *wp)
   wp->w_topfill = 0;
   wp->w_botline = 2;
   wp->w_valid = 0;
+  wp->w_last_used = 0;
   wp->w_s = &wp->w_buffer->b_s;
 }
 

test.lua

@@ -0,0 +1,8 @@
+vim.keymap.set("n", "<C-h>", function()
+    local bufnr = vim.api.nvim_get_current_buf()
+    local bufInfo = vim.fn.getbufinfo(bufnr)
+    local winid = bufInfo[1].windows[1]
+    local wininfo = vim.fn.getwininfo(winid)
+    print(wininfo[1].lastused)
+  end,
+  { silent = true, noremap = true })