feat(clipboard): enable OSC 52 clipboard provider by default (#26064)

Use the XTGETTCAP sequence to determine if the host terminal supports
the OSC 52 sequence and, if it does, enable the OSC 52 clipboard
provider by default.

This is only done automatically when all of the following are true:

  1. Nvim is running in the TUI
  2. 'clipboard' is not set to unnamed or unnamedplus
  3. g:clipboard is unset
  4. Nvim is running in an SSH connection ($SSH_TTY is set)
  5. Nvim is not running inside tmux ($TMUX is unset)

runtime/lua/vim/ui/clipboard/osc52.lua

@@ -1,60 +1,75 @@
 local M = {}
 
-function M.copy(lines)
-  local s = table.concat(lines, '\n')
-  io.stdout:write(string.format('\027]52;;%s\027\\', vim.base64.encode(s)))
+--- Return the OSC 52 escape sequence
+---
+--- @param clipboard string The clipboard to read from or write to
+--- @param contents string The Base64 encoded contents to write to the clipboard, or '?' to read
+---                        from the clipboard
+local function osc52(clipboard, contents)
+  return string.format('\027]52;%s;%s\027\\', clipboard, contents)
 end
 
-function M.paste()
-  local contents = nil
-  local id = vim.api.nvim_create_autocmd('TermResponse', {
-    callback = function(args)
-      local resp = args.data ---@type string
-      local encoded = resp:match('\027%]52;%w?;([A-Za-z0-9+/=]*)')
-      if encoded then
-        contents = vim.base64.decode(encoded)
-        return true
-      end
-    end,
-  })
+function M.copy(reg)
+  local clipboard = reg == '+' and 'c' or 's'
+  return function(lines)
+    local s = table.concat(lines, '\n')
+    io.stdout:write(osc52(clipboard, vim.base64.encode(s)))
+  end
+end
 
-  io.stdout:write('\027]52;;?\027\\')
+function M.paste(reg)
+  local clipboard = reg == '+' and 'c' or 's'
+  return function()
+    local contents = nil
+    local id = vim.api.nvim_create_autocmd('TermResponse', {
+      callback = function(args)
+        local resp = args.data ---@type string
+        local encoded = resp:match('\027%]52;%w?;([A-Za-z0-9+/=]*)')
+        if encoded then
+          contents = vim.base64.decode(encoded)
+          return true
+        end
+      end,
+    })
 
-  local ok, res
+    io.stdout:write(osc52(clipboard, '?'))
 
-  -- Wait 1s first for terminals that respond quickly
-  ok, res = vim.wait(1000, function()
-    return contents ~= nil
-  end)
+    local ok, res
 
-  if res == -1 then
-    -- If no response was received after 1s, print a message and keep waiting
-    vim.api.nvim_echo(
-      { { 'Waiting for OSC 52 response from the terminal. Press Ctrl-C to interrupt...' } },
-      false,
-      {}
-    )
-    ok, res = vim.wait(9000, function()
+    -- Wait 1s first for terminals that respond quickly
+    ok, res = vim.wait(1000, function()
       return contents ~= nil
     end)
-  end
 
-  if not ok then
-    vim.api.nvim_del_autocmd(id)
     if res == -1 then
-      vim.notify(
-        'Timed out waiting for a clipboard response from the terminal',
-        vim.log.levels.WARN
+      -- If no response was received after 1s, print a message and keep waiting
+      vim.api.nvim_echo(
+        { { 'Waiting for OSC 52 response from the terminal. Press Ctrl-C to interrupt...' } },
+        false,
+        {}
       )
-    elseif res == -2 then
-      -- Clear message area
-      vim.api.nvim_echo({ { '' } }, false, {})
+      ok, res = vim.wait(9000, function()
+        return contents ~= nil
+      end)
     end
-    return 0
-  end
 
-  -- If we get here, contents should be non-nil
-  return vim.split(assert(contents), '\n')
+    if not ok then
+      vim.api.nvim_del_autocmd(id)
+      if res == -1 then
+        vim.notify(
+          'Timed out waiting for a clipboard response from the terminal',
+          vim.log.levels.WARN
+        )
+      elseif res == -2 then
+        -- Clear message area
+        vim.api.nvim_echo({ { '' } }, false, {})
+      end
+      return 0
+    end
+
+    -- If we get here, contents should be non-nil
+    return vim.split(assert(contents), '\n')
+  end
 end
 
 return M