fix: draw user cursors upon attaching to buffer

lua/codemp/buffers.lua

@@ -6,6 +6,8 @@ local id_buffer_map = {}
 local buffer_id_map = {}
 ---@type table<string, string>
 local user_buffer_name = {}
+---@type table<string, Cursor>
+local user_cursors = {}
 local ticks = {}
 
 ---@param name string
@@ -200,6 +202,13 @@ local function attach(name, opts)
 			vim.api.nvim_set_option_value('fileformat', 'unix', { buf = buffer })
 			print(" ++ attached to buffer " .. name)
 			require('codemp.window').update()
+
+			for user, cursor in pairs(user_cursors) do
+				if cursor.sel.buffer == name then
+					local user_hl = require('codemp.workspace').map[user]
+					require('codemp.workspace').map[user].mark = utils.cursor.draw(cursor, buffer, user_hl.ns, user_hl.mark, user_hl.hi)
+				end
+			end
 		end)
 	end)
 end
@@ -251,4 +260,5 @@ return {
 	map_rev = buffer_id_map,
 	ticks = ticks,
 	users = user_buffer_name,
+	cursors = user_cursors,
 }

lua/codemp/utils.lua

@@ -71,6 +71,42 @@ local function cursor_position()
 	end
 end
 
+---@param event Cursor
+---@param buf integer
+---@param ns integer
+---@param mark integer
+---@param hi HighlightPair
+---@return integer extmark id
+local function cursor_draw(event, buf, ns, mark, hi)
+	local event_finish_2 = event.sel.end_col -- TODO can't set the tuple field? need to copy out
+	if event.sel.start_row == event.sel.end_row and event.sel.start_col == event.sel.end_col then
+		-- vim can't draw 0-width cursors, so we always expand them to at least 1 width
+		event_finish_2 = event.sel.end_col + 1
+	end
+	return vim.api.nvim_buf_set_extmark(
+		buf,
+		ns,
+		event.sel.start_row,
+		event.sel.start_col,
+		{
+			id = mark,
+			end_row = event.sel.end_row,
+			end_col = event_finish_2,
+			hl_group = hi.bg,
+			virt_text_pos = "right_align",
+			sign_text = string.sub(event.user, 0, 1),
+			sign_hl_group = hi.bg,
+			virt_text_repeat_linebreak = true,
+			priority = 1000,
+			strict = false,
+			virt_text = {
+				{ " " .. event.user .. " ", hi.fg },
+				{ " ", hi.bg },
+			},
+		}
+	)
+end
+
 
 
 --
@@ -194,6 +230,7 @@ end
 return {
 	cursor = {
 		position = cursor_position,
+		draw = cursor_draw,
 	},
 	buffer = {
 		len = buffer_len,

lua/codemp/workspace.lua

@@ -112,35 +112,10 @@ local function register_cursor_handler(controller)
 				end
 				buffers.users[event.user] = event.sel.buffer
 				local buffer_id = buffers.map_rev[event.sel.buffer]
+				buffers.cursors[event.user] = event
 				if buffer_id ~= nil then
-					local hi = user_hl[event.user].hi
-					local event_finish_2 = event.sel.end_col -- TODO can't set the tuple field? need to copy out
-					if event.sel.start_row == event.sel.end_row and event.sel.start_col == event.sel.end_col then
-						-- vim can't draw 0-width cursors, so we always expand them to at least 1 width
-						event_finish_2 = event.sel.end_col + 1
-					end
-					user_hl[event.user].mark = vim.api.nvim_buf_set_extmark(
-						buffer_id,
-						user_hl[event.user].ns,
-						event.sel.start_row,
-						event.sel.start_col,
-						{
-							id = user_hl[event.user].mark,
-							end_row = event.sel.end_row,
-							end_col = event_finish_2,
-							hl_group = hi.bg,
-							virt_text_pos = "right_align",
-							sign_text = string.sub(event.user, 0, 1),
-							sign_hl_group = hi.bg,
-							virt_text_repeat_linebreak = true,
-							priority = 1000,
-							strict = false,
-							virt_text = {
-								{ " " .. event.user .. " ", hi.fg },
-								{ " ", hi.bg },
-							},
-						}
-					)
+					local hl = user_hl[event.user]
+					user_hl[event.user].mark = utils.cursor.draw(event, buffer_id, hl.ns, hl.mark, hl.hi)
 				end
 				if old_buffer ~= event.sel.buffer then
 					require('codemp.window').update() -- redraw user positions