update lua API to 1-based indices; add renderer

lua/u/txtobj.lua

@@ -0,0 +1,45 @@
+local Range = require 'u.range'
+
+local M = {}
+
+local ESC = vim.api.nvim_replace_termcodes('<Esc>', true, false, true)
+
+--- @param key_seq string
+--- @param fn fun(key_seq: string):u.Range|nil
+--- @param opts? { buffer: number|nil }
+function M.define(key_seq, fn, opts)
+  if opts ~= nil and opts.buffer == 0 then opts.buffer = vim.api.nvim_get_current_buf() end
+
+  local function handle_visual()
+    local range = fn(key_seq)
+    if range == nil or range:is_empty() then
+      vim.cmd.normal(ESC)
+      return
+    end
+    range:set_visual_selection()
+  end
+  vim.keymap.set({ 'x' }, key_seq, handle_visual, opts and { buffer = opts.buffer } or nil)
+
+  local function handle_normal()
+    local range = fn(key_seq)
+    if range == nil then return end
+
+    if not range:is_empty() then
+      range:set_visual_selection()
+    else
+      local original_eventignore = vim.go.eventignore
+      vim.go.eventignore = 'all'
+
+      -- insert a single space, so we can select it:
+      local p = range.start
+      p:insert_before ' '
+      vim.go.eventignore = original_eventignore
+
+      -- select the space:
+      Range.new(p, p, 'v'):set_visual_selection()
+    end
+  end
+  vim.keymap.set({ 'o' }, key_seq, handle_normal, opts and { buffer = opts.buffer } or nil)
+end
+
+return M