From 49544069a2615d9197380a11441aca4eeb02afb3 Mon Sep 17 00:00:00 2001
From: Albert Krewinkel <albert+github@zeitkraut.de>
Date: Sun, 14 Oct 2018 08:20:29 +0200
Subject: [PATCH] Custom writer: give full access to doc in optional Setup
function (#4967)
Custom writers can specify an optional `Setup` function. The function
takes the full Pandoc document as input and should not return any value.
Users can use this function to configure the writer depending on the
given document's content or its metadata.
data/sample.lua: add sample use of Setup function.
The change allows to control the image format used to encode the image
produced from dot code.
Closes #4957
---
data/sample.lua | 37 ++++++++++++++++++++++++++++---
src/Text/Pandoc/Writers/Custom.hs | 17 +++++++++++++-
2 files changed, 50 insertions(+), 4 deletions(-)
diff --git a/data/sample.lua b/data/sample.lua
index e25bf59cb..019ac13f3 100644
--- a/data/sample.lua
+++ b/data/sample.lua
@@ -2,7 +2,8 @@
-- that is very similar to that of pandoc's HTML writer.
-- There is one new feature: code blocks marked with class 'dot'
-- are piped through graphviz and images are included in the HTML
--- output using 'data:' URLs.
+-- output using 'data:' URLs. The image format can be controlled
+-- via the `image_format` metadata field.
--
-- Invoke with: pandoc -t sample.lua
--
@@ -13,6 +14,32 @@
-- syntax errors.
local pipe = pandoc.pipe
+local stringify = (require "pandoc.utils").stringify
+
+local image_format = "png"
+local image_mime_type = "image/png"
+
+-- Get the mime type for a given format.
+local function mime_type(img_format)
+ local formats = {
+ jpeg = "image/jpeg",
+ jpg = "image/jpeg",
+ gif = "image/gif",
+ png = "image/png",
+ svg = "image/svg+xml",
+ }
+ return formats[img_format]
+ or error("unsupported image format `" .. img_format .. "`")
+end
+
+-- Set options from document metadata.
+function Setup(doc)
+ local meta = doc.meta
+ if meta.image_format then
+ image_format = stringify(meta.image_format)
+ image_mime_type = mime_type(image_format)
+ end
+end
-- Character escaping
local function escape(s, in_attribute)
@@ -206,8 +233,8 @@ function CodeBlock(s, attr)
-- If code block has class 'dot', pipe the contents through dot
-- and base64, and include the base64-encoded png as a data: URL.
if attr.class and string.match(' ' .. attr.class .. ' ',' dot ') then
- local png = pipe("base64", {}, pipe("dot", {"-Tpng"}, s))
- return '<img src="data:image/png;base64,' .. png .. '"/>'
+ local img = pipe("base64", {}, pipe("dot", {"-T" .. image_format}, s))
+ return '<img src="data:' .. image_mime_type .. ';base64,' .. img .. '"/>'
-- otherwise treat as code (one could pipe through a highlighter)
else
return "<pre><code" .. attributes(attr) .. ">" .. escape(s) ..
@@ -325,6 +352,10 @@ end
local meta = {}
meta.__index =
function(_, key)
+ -- Setup is optional, don't warn if it's not present.
+ if key == 'Setup' then
+ return
+ end
io.stderr:write(string.format("WARNING: Undefined function '%s'\n",key))
return function() return "" end
end
diff --git a/src/Text/Pandoc/Writers/Custom.hs b/src/Text/Pandoc/Writers/Custom.hs
index 37fec9f0f..a5b0ed169 100644
--- a/src/Text/Pandoc/Writers/Custom.hs
+++ b/src/Text/Pandoc/Writers/Custom.hs
@@ -116,7 +116,7 @@ writeCustom luaFile opts doc@(Pandoc meta _) = do
-- to handle this more gracefully):
when (stat /= Lua.OK) $
Lua.tostring' (-1) >>= throw . PandocLuaException . UTF8.toString
- -- TODO - call hierarchicalize, so we have that info
+ runSetup doc
rendered <- docToCustom opts doc
context <- metaToJSON opts
blockListToCustom
@@ -133,6 +133,21 @@ writeCustom luaFile opts doc@(Pandoc meta _) = do
Left e -> throw (PandocTemplateError e)
Right r -> return (pack r)
+-- | Try to call a setup function. The function, if it exists, is passed the
+-- full pandoc document as parameter. This allows users to setup the writer
+-- depending on the content of the document. Accessing information on the
+-- document hierarchy is possible via the `pandoc.utils.hierarchicalize`
+-- function.
+runSetup :: Pandoc -> Lua ()
+runSetup doc = do
+ Lua.getglobal "Setup"
+ setup <- Lua.ltype Lua.stackTop
+ if setup /= Lua.TypeFunction
+ then Lua.pop 1
+ else do
+ Lua.push doc
+ Lua.call 1 0
+
docToCustom :: WriterOptions -> Pandoc -> Lua String
docToCustom opts (Pandoc (Meta metamap) blocks) = do
body <- blockListToCustom blocks