perf: registers freeze nvim when they contain large content

lua/which-key/config.lua

@@ -39,7 +39,20 @@ local defaults = {
   end,
   plugins = {
     marks = true, -- shows a list of your marks on ' and `
-    registers = true, -- shows your registers on " in NORMAL or <C-r> in INSERT mode
+    registers = {
+      enabled = true, -- shows your registers on " in NORMAL or <C-r> in INSERT mode
+      -- Format function for register values. Accepts a string and returns a formatted string.
+      -- Useful for truncating long register contents to prevent UI freezing.
+      -- The default truncates at 100 characters to balance readability and performance.
+      ---@type fun(value: string): string
+      format = function(value)
+        local max_len = 100 -- Truncate after 100 characters to prevent UI freezing
+        if #value > max_len then
+          return value:sub(1, max_len) .. "…"
+        end
+        return value
+      end,
+    },
     -- the presets plugin, adds help for a bunch of default keybindings in Neovim
     -- No actual key bindings are created
     spelling = {

lua/which-key/plugins/registers.lua

@@ -37,12 +37,29 @@ M.replace = {
   ["\r"] = "",
 }
 
+-- Cache the format function to avoid repeated lookups
+local format_fn = nil
+local format_fn_initialized = false
+
+local function get_format_fn()
+  if not format_fn_initialized then
+    local Config = require("which-key.config")
+    if type(Config.plugins.registers) == "table" and type(Config.plugins.registers.format) == "function" then
+      format_fn = Config.plugins.registers.format
+    end
+    format_fn_initialized = true
+  end
+  return format_fn
+end
+
 function M.expand()
   local items = {} ---@type wk.Plugin.item[]
 
   local is_osc52 = vim.g.clipboard and vim.g.clipboard.name == "OSC 52"
   local has_clipboard = vim.g.loaded_clipboard_provider == 2
 
+  local format_func = get_format_fn()
+
   for i = 1, #M.registers, 1 do
     local key = M.registers:sub(i, i)
     local value = ""
@@ -57,6 +74,10 @@ function M.expand()
       for k, v in pairs(M.replace) do
         value = value:gsub(k, v) --[[@as string]]
       end
+      -- Apply format function if configured
+      if format_func then
+        value = format_func(value)
+      end
       table.insert(items, { key = key, desc = labels[key] or "", value = value })
     end
   end