Give readme headings anchors like GitHub's

A readme's links to its own sections, as in a table of contents, had
nothing on the page to land on.

1 file changed, 36 insertions, 1 deletion

diff --git a/custom/extensions/about-render.lua b/custom/extensions/about-render.luaindex 73b1336..6ee790b 100644--- a/custom/extensions/about-render.lua+++ b/custom/extensions/about-render.lua@@ -32,6 +32,10 @@ local max_depth = 24  local filename, tree_base, tree_query, chunks = "", "", "", {} +-- How often each heading anchor has been handed out. The ids already on the+-- page around the readme start at one, so no heading takes them.+local id_counts = {}+  -- Lua patterns backtrack, so "%s+$" costs the square of a run of spaces in -- the middle of a line. Finding each end directly stays linear.@@ -204,6 +208,34 @@ local function shows_something(lines) 	return false end +local function plain_text(nodes, parts)+	for _, node in ipairs(nodes) do+		if node.kind == "text" or node.kind == "code" then+			parts[#parts + 1] = node.text+		elseif node.kids then+			plain_text(node.kids, parts)+		end+	end+	return parts+end++-- Gives a heading the anchor GitHub would, so a readme's links to its own+-- sections work. That is its text in lower case, with punctuation dropped+-- and each space a hyphen, and a count added to a repeat. Bytes past ASCII+-- stay, keeping the letters of other scripts.+local function emit_id(nodes)+	local base = table.concat(plain_text(nodes, {})):lower()+		:gsub("[^%w_%- \128-\255]", ""):gsub(" ", "-")+	if base == "" then+		return+	end+	local count = id_counts[base] or 0+	id_counts[base] = count + 1+	html(" id='")+	html_attr(count > 0 and base .. "-" .. count or base)+	html("'")+end+ local function emit_lines(lines) 	for i, line in ipairs(lines) do 		if i > 1 then@@ -219,7 +251,9 @@ emit_blocks = function(blocks) 	for _, block in ipairs(blocks) do 		local kind = block.kind 		if kind == "heading" then-			html("<h" .. block.level .. ">")+			html("<h" .. block.level)+			emit_id(block.kids)+			html(">") 			emit_inline(block.kids) 			html("</h" .. block.level .. ">") 		elseif kind == "hr" then@@ -778,6 +812,7 @@ function filter_open(name, base, query) 	tree_base = base or "" 	tree_query = query or "" 	chunks = {}+	id_counts = { cgit = 1, header = 1, about = 1 } end  function filter_write(str)
diff --git a/custom/extensions/about-render.lua b/custom/extensions/about-render.lua
index 73b1336..6ee790b 100644
--- a/custom/extensions/about-render.lua
+++ b/custom/extensions/about-render.lua
@@ -32,6 +32,10 @@ local max_depth = 24
 
 local filename, tree_base, tree_query, chunks = "", "", "", {}
 
+-- How often each heading anchor has been handed out. The ids already on the
+-- page around the readme start at one, so no heading takes them.
+local id_counts = {}
+
 
 -- Lua patterns backtrack, so "%s+$" costs the square of a run of spaces in
 -- the middle of a line. Finding each end directly stays linear.
@@ -204,6 +208,34 @@ local function shows_something(lines)
 	return false
 end
 
+local function plain_text(nodes, parts)
+	for _, node in ipairs(nodes) do
+		if node.kind == "text" or node.kind == "code" then
+			parts[#parts + 1] = node.text
+		elseif node.kids then
+			plain_text(node.kids, parts)
+		end
+	end
+	return parts
+end
+
+-- Gives a heading the anchor GitHub would, so a readme's links to its own
+-- sections work. That is its text in lower case, with punctuation dropped
+-- and each space a hyphen, and a count added to a repeat. Bytes past ASCII
+-- stay, keeping the letters of other scripts.
+local function emit_id(nodes)
+	local base = table.concat(plain_text(nodes, {})):lower()
+		:gsub("[^%w_%- \128-\255]", ""):gsub(" ", "-")
+	if base == "" then
+		return
+	end
+	local count = id_counts[base] or 0
+	id_counts[base] = count + 1
+	html(" id='")
+	html_attr(count > 0 and base .. "-" .. count or base)
+	html("'")
+end
+
 local function emit_lines(lines)
 	for i, line in ipairs(lines) do
 		if i > 1 then
@@ -219,7 +251,9 @@ emit_blocks = function(blocks)
 	for _, block in ipairs(blocks) do
 		local kind = block.kind
 		if kind == "heading" then
-			html("<h" .. block.level .. ">")
+			html("<h" .. block.level)
+			emit_id(block.kids)
+			html(">")
 			emit_inline(block.kids)
 			html("</h" .. block.level .. ">")
 		elseif kind == "hr" then
@@ -778,6 +812,7 @@ function filter_open(name, base, query)
 	tree_base = base or ""
 	tree_query = query or ""
 	chunks = {}
+	id_counts = { cgit = 1, header = 1, about = 1 }
 end
 
 function filter_write(str)