feat(terminal): follow output by default, toggle with G

Terminal buffers track their latest output by default: leaving
terminal mode or the window, and re-entering the window, jumps to the
bottom (G). Toggle per terminal with G in terminal mode or the
:TerminalFollow command; an active follow shows as +T in the
statusline.

1 files changed, 53 insertions, 4 deletions

diff --git a/init.lua b/init.lua
index 1ba8311..c14246a 100644
--- a/init.lua
+++ b/init.lua
@@ -73,6 +73,38 @@ local function terminal_put_register()
 	vim.api.nvim_put({ value }, "c", true, true)
 end
 
+-- Toggle "follow" mode for the current terminal: while on, leaving terminal mode or the terminal
+-- window jumps to the bottom (G) so the view tracks the latest output. Shown as `+T` in the
+-- statusline (50-color.lua).
+local function toggle_terminal_follow()
+	if vim.bo.buftype ~= "terminal" then
+		vim.notify("TerminalFollow only applies to terminal buffers", vim.log.levels.WARN)
+		return
+	end
+	vim.b.terminal_follow = not vim.b.terminal_follow
+end
+
+-- Enter terminal mode and follow output by default when a terminal opens
+local function terminal_open()
+	vim.b.terminal_follow = true
+	vim.cmd.startinsert()
+end
+
+-- Jump to the bottom (G) when follow mode is on, so the view tracks the latest terminal output
+local function terminal_follow_to_bottom()
+	if vim.b.terminal_follow then
+		vim.cmd.normal({ "G", bang = true })
+	end
+end
+
+-- Keep following after entering a terminal window: defer so a mouse click's cursor placement runs
+-- first, then override it with G
+local function terminal_follow_on_enter()
+	if vim.b.terminal_follow then
+		vim.schedule(terminal_follow_to_bottom)
+	end
+end
+
 -- Kill from the cursor to the end of the command line, akin to Readline's kill-line
 local function cmdline_kill_line()
 	local pos = vim.fn.getcmdpos() -- 1-based byte index of the cursor
@@ -134,6 +166,11 @@ vim.api.nvim_create_user_command(
 	show_buf_diff_orig,
 	{ desc = "Show diff between current buffer and file" }
 )
+vim.api.nvim_create_user_command(
+	"TerminalFollow",
+	toggle_terminal_follow,
+	{ desc = "Toggle following terminal output" }
+)
 
 ------------------------------------------------------------------------------------------------------------------------
 -- Keymaps (there's more in the different plugins)
@@ -187,11 +224,23 @@ vim.keymap.set("t", "<Esc>", "<C-\\><C-n>", { desc = "Exit terminal mode" })
 vim.keymap.set("t", "<M-[>", "<Esc>", { desc = "Send <Esc> to the terminal program" })
 vim.keymap.set("t", "<C-o>", "<C-\\><C-o>", { desc = "Execute one normal-mode command" })
 vim.keymap.set("t", "<C-r>", terminal_put_register, { desc = "Paste register" })
+vim.keymap.set("t", "G", "<Cmd>TerminalFollow<CR>", { desc = "Toggle following terminal output" })
 -- stylua: ignore end
-vim.api.nvim_create_autocmd(
-	"TermOpen",
-	{ pattern = "*", command = "startinsert", desc = "Enter terminal mode" }
-)
+vim.api.nvim_create_autocmd("TermOpen", {
+	desc = "Follow terminal output by default",
+	group = vim.g.dotfiles.augroup,
+	callback = terminal_open,
+})
+vim.api.nvim_create_autocmd({ "TermLeave", "WinLeave" }, {
+	desc = "Follow terminal output",
+	group = vim.g.dotfiles.augroup,
+	callback = terminal_follow_to_bottom,
+})
+vim.api.nvim_create_autocmd("WinEnter", {
+	desc = "Follow terminal output",
+	group = vim.g.dotfiles.augroup,
+	callback = terminal_follow_on_enter,
+})
 
 ------------------------------------------------------------------------------------------------------------------------
 -- Options