feat(defaults): enable 'termguicolors' by default when supported by terminal

Enable 'termguicolors' automatically when Nvim can detect that truecolor
is supported by the host terminal.

If $COLORTERM is set to "truecolor" or "24bit", or the terminal's
terminfo entry contains capabilities for Tc, RGB, or setrgbf and
setrgbb, then we assume that the terminal supports truecolor. Otherwise,
the terminal is queried (using both XTGETTCAP and SGR + DECRQSS). If the
terminal's response to these queries (if any) indicates that it supports
truecolor, then 'termguicolors' is enabled.

1 files changed, 42 insertions, 10 deletions

diff --git a/runtime/lua/vim/termcap.lua b/runtime/lua/vim/termcap.lua
index 862cc52149..b88d9ac9ba 100644
--- a/runtime/lua/vim/termcap.lua
+++ b/runtime/lua/vim/termcap.lua
@@ -12,7 +12,10 @@ local M = {}
 --- emulator supports the XTGETTCAP sequence.
 ---
 --- @param caps string|table A terminal capability or list of capabilities to query
---- @param cb function(cap:string, seq:string) Function to call when a response is received
+--- @param cb function(cap:string, found:bool, seq:string?) Callback function which is called for
+---           each capability in {caps}. {found} is set to true if the capability was found or false
+---           otherwise. {seq} is the control sequence for the capability if found, or nil for
+---           boolean capabilities.
 function M.query(caps, cb)
   vim.validate({
     caps = { caps, { 'string', 'table' } },
@@ -23,21 +26,33 @@ function M.query(caps, cb)
     caps = { caps }
   end
 
-  local count = #caps
+  local pending = {} ---@type table<string, boolean>
+  for _, v in ipairs(caps) do
+    pending[v] = true
+  end
+
+  local timer = assert(vim.uv.new_timer())
 
-  vim.api.nvim_create_autocmd('TermResponse', {
+  local id = vim.api.nvim_create_autocmd('TermResponse', {
     callback = function(args)
       local resp = args.data ---@type string
-      local k, v = resp:match('^\027P1%+r(%x+)=(%x+)$')
-      if k and v then
+      local k, rest = resp:match('^\027P1%+r(%x+)(.*)$')
+      if k and rest then
         local cap = vim.text.hexdecode(k)
-        local seq =
-          vim.text.hexdecode(v):gsub('\\E', '\027'):gsub('%%p%d', ''):gsub('\\(%d+)', string.char)
+        local seq ---@type string?
+        if rest:match('^=%x+$') then
+          seq = vim.text
+            .hexdecode(rest:sub(2))
+            :gsub('\\E', '\027')
+            :gsub('%%p%d', '')
+            :gsub('\\(%d+)', string.char)
+        end
+
+        cb(cap, true, seq)
 
-        cb(cap, seq)
+        pending[cap] = nil
 
-        count = count - 1
-        if count == 0 then
+        if next(pending) == nil then
           return true
         end
       end
@@ -57,6 +72,23 @@ function M.query(caps, cb)
   end
 
   io.stdout:write(query)
+
+  timer:start(1000, 0, function()
+    -- Delete the autocommand if no response was received
+    vim.schedule(function()
+      -- Suppress error if autocommand has already been deleted
+      pcall(vim.api.nvim_del_autocmd, id)
+
+      -- Call the callback for all capabilities that were not found
+      for k in pairs(pending) do
+        cb(k, false, nil)
+      end
+    end)
+
+    if not timer:is_closing() then
+      timer:close()
+    end
+  end)
 end
 
 return M