Mermaid options to configure mmdc

README.md

@@ -231,6 +231,43 @@ diagram:
 ---
 ```
 
+#### Mermaid
+
+The Mermaid engine accepts various options corresponding to
+a subset of the options that the `mmdc` command can take:
+
+- `theme`: passes its value to `--theme`
+- `background-color`: passes its value to `--backgroundColor`
+- `config-file`: passes its value to `--configFile`
+- `css-file`: passes its value to `--cssFile`
+- `scale`: passes its value to `--scale`
+- `puppeteer-config-file`: passes its value to `--puppeteerConfigFile`
+- `icon-packs`: passes its value to `--iconPacks`
+
+For more in-depth information on the meaning and format of every
+option, use `mmdc --help`.
+
+*Note* that for options that need to receive a file (e.g. `config-file`), relative paths can be used.
+However they will be *relative to the working directory used when calling the `pandoc`
+executable*, not to the directory of the file that contains the metadata block.
+
+Example:
+
+``` yaml
+---
+diagram:
+  engine:
+    mermaid:
+      theme: forest
+      background-color: white
+      config-file: mermaidConfig.json
+      css-file: cssFile.css
+      scale: 1
+      puppeteer-config-file: puppeteerConfig.json
+      icon-packs: "@iconify-json/logos"
+---
+```
+
 Security
 --------
 

_extensions/diagram/diagram.lua

@@ -152,17 +152,30 @@ local mermaid = {
     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)
-      return with_working_directory(tmpdir, function ()
-        local infile = 'diagram.mmd'
-        local outfile = 'diagram.' .. file_extension
-        write_file(infile, code)
-        pipe(
-          self.execpath or 'mmdc',
-          {"--pdfFit", "--input", infile, "--output", outfile},
-          ''
-        )
-        return read_file(outfile), mime_type
-      end)
+      local infile = pandoc.path.join({tmpdir, 'diagram.mmd'})
+      local outfile = pandoc.path.join({tmpdir, 'diagram.' .. file_extension})
+      --- Configure options for mmdc based on engine options
+      local args = List{'--pdfFit', '--input', infile, '--output', outfile}
+      if self.opt then
+        local options = {
+          ['theme'] = '--theme',
+          ['background-color'] = '--backgroundColor',
+          ['config-file'] = '--configFile',
+          ['css-file'] = '--cssFile',
+          ['scale'] = '--scale',
+          ['puppeteer-config-file'] = '--puppeteerConfigFile',
+          ['icon-packs'] = '--iconPacks',
+        }
+        for opt, cliopt in pairs(options) do
+          if self.opt[opt] then
+            args:insert(cliopt)
+            args:insert(stringify(self.opt[opt]))
+          end
+        end
+      end
+      write_file(infile, code)
+      pipe(self.execpath or 'mmdc', args, '')
+      return read_file(outfile), mime_type
     end)
   end,
 }

test/mermaidConfig.json

@@ -0,0 +1 @@
+{}

test/puppeteerConfig.json

@@ -0,0 +1 @@
+{}

test/test-mermaid.yaml

@@ -6,5 +6,14 @@ metadata:
   pagetitle: Mermaid diagram
   diagram:
     cache: false
+    engine:
+      mermaid:
+        theme: forest
+        background-color: white
+        config-file: test/mermaidConfig.json
+        css-file: test/cssFile.css
+        scale: 1
+        puppeteer-config-file: test/puppeteerConfig.json
+        icon-packs: "@iconify-json/logos"
 variables:
   document-css: false