Add fullscreen toggle for neovim

.config/nvim/lua/config/keymaps.lua

@@ -2,6 +2,10 @@
 -- Default keymaps that are always set: https://github.com/LazyVim/LazyVim/blob/main/lua/lazyvim/config/keymaps.lua
 -- Add any additional keymaps here
 
+local max_height = vim.o.lines
+local max_width = vim.o.columns
+local fullscreen_inset = 2
+
 function toggle_background()
   if vim.opt.background:get() == "dark" then
     vim.opt.background = "light"
@@ -10,4 +14,46 @@ function toggle_background()
   end
 end
 
-vim.keymap.set("n", "<F5>", "<cmd>lua toggle_background()<cr>", { desc = "Switch between dark and light themes", noremap = true })
+function ToggleFullscreen()
+  local bufid = vim.api.nvim_get_current_buf()
+  local winid = vim.api.nvim_get_current_win()
+
+  local fullscreen_win = vim.w.fullscreen_win
+  if fullscreen_win then
+    vim.api.nvim_win_close(winid, false)
+    return
+  end
+
+  for _, id in ipairs(vim.api.nvim_list_wins()) do
+    local res
+    res, fullscreen_win = pcall(function()
+      return vim.api.nvim_win_get_var(id, "fullscreen_win")
+    end)
+    if res and fullscreen_win then
+      vim.api.nvim_set_current_win(id)
+      vim.print(true)
+      return
+    end
+  end
+
+  winid = vim.api.nvim_open_win(bufid, true, {
+    relative = "editor",
+    border = "rounded",
+    row = fullscreen_inset,
+    col = fullscreen_inset,
+    width = max_width - fullscreen_inset - fullscreen_inset,
+    height = max_height - fullscreen_inset - fullscreen_inset - 1,
+    title = "Fullscreen (" .. vim.api.nvim_buf_get_name(bufid) .. ")",
+    title_pos = "center",
+  })
+  vim.api.nvim_win_set_var(winid, "fullscreen_win", true)
+end
+
+vim.keymap.set(
+  "n",
+  "<F5>",
+  "<cmd>lua toggle_background()<cr>",
+  { desc = "Switch between dark and light themes", noremap = true }
+)
+
+vim.keymap.set("n", "<leader>m", ToggleFullscreen, { desc = "Maximize window", noremap = true })