--- stuff\diagram-og.lua	2026-05-30 03:52:48.703616700 +0700
+++ stuff\diagram.lua	2026-05-30 06:45:13.472927700 +0700
@@ -6,6 +6,14 @@
 -- The filter uses the Figure AST element, which was added in pandoc 3.
 PANDOC_VERSION:must_be_at_least '3.0'
 
+warn = warn or function (...)
+  local parts = {}
+  for i = 1, select('#', ...) do
+    parts[#parts+1] = tostring(select(i, ...))
+  end
+  io.stderr:write(table.concat(parts, '') .. '\n')
+end
+
 local version = pandoc.types.Version '1.2.0'
 
 -- Report Lua warnings to stderr if the `warn` function is not plugged into
@@ -148,7 +156,7 @@
 local mermaid = {
   line_comment_start = '%%',
   mime_types = mime_types_set{'pdf', 'png', 'svg'},
-  compile = function (self, code)
+  compile = function (self, code, user_opts)
     local mime_type = self.mime_type or 'image/svg+xml'
     local file_extension = extension_for_mimetype[mime_type]
     return with_temporary_directory("diagram", function (tmpdir)
@@ -156,11 +164,30 @@
         local infile = 'diagram.mmd'
         local outfile = 'diagram.' .. file_extension
         write_file(infile, code)
-        pipe(
-          self.execpath or 'mmdc',
-          {"--pdfFit", "--input", infile, "--output", outfile},
-          ''
-        )
+
+        local args = {"--pdfFit", "--input", infile, "--output", outfile}
+
+        -- Map YAML options to mmdc flags
+        if user_opts then
+          local opt_map = {
+            theme           = '--theme',
+            backgroundColor = '--backgroundColor',
+            width           = '--width',
+            height          = '--height',
+            scale           = '--scale',
+            configFile      = '--configFile',
+            cssFile         = '--cssFile',
+            outputFormat    = '--outputFormat',
+          }
+          for key, flag in pairs(opt_map) do
+            if user_opts[key] then
+              table.insert(args, flag)
+              table.insert(args, stringify(user_opts[key]))
+            end
+          end
+        end
+
+        pipe(self.execpath or 'mmdc', args, '')
         return read_file(outfile), mime_type
       end)
     end)
@@ -223,11 +250,11 @@
           ''
         )
         if not success then
-          warn(string.format(
-                 "The call\n%s\nfailed with error code %s. Output:\n%s",
-                 result.command,
-                 result.error_code,
-                 result.output
+          io.stderr:write(string.format(
+                 "The call\n%s\nfailed with error code %s. Output:\n%s\n",
+                 tostring(result and result.command),
+                 tostring(result and result.error_code),
+                 tostring(result and result.output)
           ))
         end
         return read_file(pdf_file), 'application/pdf'
@@ -385,7 +412,7 @@
 
   -- Sanity check
   if not engine then
-    warn(PANDOC_SCRIPT_FILE, ": No such engine '", name, "'.")
+    io.stderr:write(PANDOC_SCRIPT_FILE .. ": No such engine '" .. name .. "'.\n")
     return nil
   elseif engopts == false then
     -- engine is disabled
@@ -402,7 +429,7 @@
     engopts['mime-type'] or engopts['mime-types']
   )
   if not mime_type then
-    warn(PANDOC_SCRIPT_FILE, ": Cannot use ", name, " with ", format.name)
+    io.stderr:write(PANDOC_SCRIPT_FILE .. ": Cannot use " .. name .. " with " .. format.name .. "\n")
     return nil
   end
 
@@ -600,13 +627,13 @@
       -- Bail if an error occurred; imgdata contains the error message
       -- when that happens.
       if not success then
-        warn(PANDOC_SCRIPT_FILE, ': ', tostring(imgdata))
+        io.stderr:write(PANDOC_SCRIPT_FILE .. ': ' .. tostring(imgdata) .. '\n')
         return nil
       elseif not imgdata then
-        warn(PANDOC_SCRIPT_FILE, ': Diagram engine returned no image data.')
+        io.stderr:write(PANDOC_SCRIPT_FILE .. ': Diagram engine returned no image data.\n')
         return nil
       elseif not imgtype then
-        warn(PANDOC_SCRIPT_FILE, ': Diagram engine did not return a MIME type.')
+        io.stderr:write(PANDOC_SCRIPT_FILE .. ': Diagram engine did not return a MIME type.\n')
         return nil
       end