feat(terminal): trigger TermRequest autocommand events (#22159)

This commit implements a new TermRequest autocommand event and has Neovim
emit this event when children of terminal buffers emit an OSC or DCS sequence
libvterm does not handle.

The TermRequest autocommand event has additional data in the
v:termrequest variable.

Co-authored-by: Gregory Anders <greg@gpanders.com>

1 files changed, 55 insertions, 0 deletions

diff --git a/test/functional/terminal/tui_spec.lua b/test/functional/terminal/tui_spec.lua
index f6ee0f9c77..e65e57bc7f 100644
--- a/test/functional/terminal/tui_spec.lua
+++ b/test/functional/terminal/tui_spec.lua
@@ -28,6 +28,7 @@ local new_pipename = helpers.new_pipename
 local spawn_argv = helpers.spawn_argv
 local set_session = helpers.set_session
 local write_file = helpers.write_file
+local eval = helpers.eval
 
 if helpers.skip(is_os('win')) then
   return
@@ -2736,6 +2737,42 @@ describe('TUI', function()
       unchanged = true,
     }
   end)
+
+  it('queries the terminal for truecolor support', function()
+    clear()
+    exec_lua([[
+      vim.api.nvim_create_autocmd('TermRequest', {
+        callback = function(args)
+          local req = args.data
+          local payload = req:match('^\027P%+q([%x;]+)$')
+          if payload then
+            vim.g.xtgettcap = true
+            return true
+          end
+        end,
+      })
+    ]])
+    screen = thelpers.setup_child_nvim({
+      '-u',
+      'NONE',
+      '-i',
+      'NONE',
+    }, {
+      env = {
+        VIMRUNTIME = os.getenv('VIMRUNTIME'),
+
+        -- Force COLORTERM to be unset and use a TERM that does not contain Tc or RGB in terminfo.
+        -- This will force the nested nvim instance to query with XTGETTCAP
+        COLORTERM = '',
+        TERM = 'xterm-256colors',
+      },
+    })
+
+    retry(nil, 1000, function()
+      eq(true, eval("get(g:, 'xtgettcap', v:false)"))
+      eq(1, eval('&termguicolors'))
+    end)
+  end)
 end)
 
 describe('TUI bg color', function()
@@ -2743,6 +2780,18 @@ describe('TUI bg color', function()
 
   local function setup_bg_test()
     clear()
+    exec_lua([[
+      vim.api.nvim_create_autocmd('TermRequest', {
+        callback = function(args)
+          local req = args.data
+          if req == '\027]11;?' then
+            vim.g.oscrequest = true
+            return true
+          end
+        end,
+      })
+    ]])
+
     screen = thelpers.setup_child_nvim({
       '-u',
       'NONE',
@@ -2759,6 +2808,12 @@ describe('TUI bg color', function()
 
   before_each(setup_bg_test)
 
+  it('queries the terminal for background color', function()
+    retry(nil, 1000, function()
+      eq(true, eval("get(g:, 'oscrequest', v:false)"))
+    end)
+  end)
+
   it('triggers OptionSet event on unsplit terminal-response', function()
     screen:expect([[
       {1: }                                                 |