feat(toc): add config for enabling synchronized cursorline in toc window

lua/neorg/modules/core/qol/toc/module.lua

@@ -55,8 +55,15 @@ module.config.public = {
     -- A function that takes node type as argument and returns true if this
     -- type of node should appear in the Table of Contents
     toc_filter = function(node_type) return node_type:match("^heading") end,
+
+    -- If `true`, `cursurline` will be enabled (highlighted) in the ToC window,
+    -- and the cursor position between ToC and content window will be synchronized.
+    sync_cursorline = true,
 }
 
+local start_lines_of_toc_buf = {}
+local last_row_of_norg_win = {}
+
 module.public = {
     parse_toc_macro = function(buffer)
         local toc, toc_name = false, nil
@@ -153,6 +160,8 @@ module.public = {
 
         local prefix, title
         local extmarks = {}
+        local start_lines = { offset = offset }
+        start_lines_of_toc_buf[ui_buffer] = start_lines
         local toc_filter = module.config.public.toc_filter
 
         local success = module.required["core.integrations.treesitter"].execute_query(
@@ -181,11 +190,15 @@ module.public = {
 
                 if prefix and title then
                     local _, column = title:start()
+
                     table.insert(
                         extmarks,
                         vim.api.nvim_buf_set_extmark(original_buffer, namespace, (prefix:start()), column, {})
                     )
 
+                    local row_0b, _, _, _ = node:range()
+                    table.insert(start_lines, row_0b)
+
                     local prefix_text =
                         module.required["core.integrations.treesitter"].get_node_text(prefix, original_buffer)
                     local title_text =
@@ -246,6 +259,24 @@ local function get_max_virtcol()
     return result
 end
 
+local function upper_bound(array, v)
+    -- assume array is sorted
+    -- find index of first element in array that is > v
+    local l = 1
+    local r = #array
+
+    while l <= r do
+        local m = math.floor((l+r)/2)
+        if v >= array[m] then
+            l = m + 1
+        else
+            r = m - 1
+        end
+    end
+
+    return l
+end
+
 module.on_event = function(event)
     if event.split_type[2] ~= module.name then
         return
@@ -276,6 +307,10 @@ module.on_event = function(event)
 
     vim.api.nvim_win_set_option(window, "scrolloff", 999)
     vim.api.nvim_win_set_option(window, "conceallevel", 0)
+    if module.config.public.sync_cursorline then
+        vim.api.nvim_win_set_option(window, "cursorline", true)
+    end
+
     module.public.update_toc(namespace, toc_title, event.buffer, event.window, buffer, window)
 
     if module.config.public.fit_width then
@@ -336,6 +371,34 @@ module.on_event = function(event)
                 module.public.update_toc(namespace, toc_title, buf, previous_window, buffer, window)
             end,
         })
+
+        if module.config.public.sync_cursorline then
+            vim.api.nvim_create_autocmd({"CursorMoved", "CursorMovedI"}, {
+                -- pattern = "*.norg",
+                buffer = previous_buffer,
+                callback = function(ev)
+                    assert(ev.buf == previous_buffer)
+                    local content_window = vim.fn.bufwinid(ev.buf)
+
+                    if not vim.api.nvim_buf_is_valid(buffer) or not vim.api.nvim_buf_is_loaded(buffer) then
+                        return true
+                    end
+
+                    local current_row_1b = vim.fn.line('.', content_window)
+                    if last_row_of_norg_win[content_window] == current_row_1b then
+                        return
+                    end
+                    last_row_of_norg_win[content_window] = current_row_1b
+
+                    local start_lines = start_lines_of_toc_buf[buffer]
+                    assert(start_lines)
+
+                    local current_toc_item_idx = upper_bound(start_lines, current_row_1b-1) - 1
+                    local current_toc_row = current_toc_item_idx==0 and 1 or current_toc_item_idx + start_lines.offset
+                    vim.api.nvim_win_set_cursor(window, { current_toc_row, 0 })
+                end,
+            })
+        end
     end
 end