From 3b0687e5571c2091ce582200d2fd7e15222d3efc Mon Sep 17 00:00:00 2001
From: NicolasNewman <nanewman01@gmail.com>
Date: Mon, 22 Apr 2024 17:12:12 -0500
Subject: [PATCH] feat(mathml): added additional config option for forcing
 legacy rendering

---
 packages/mermaid/src/config.type.ts             | 7 +++++++
 packages/mermaid/src/diagrams/common/common.ts  | 5 +++--
 packages/mermaid/src/schemas/config.schema.yaml | 7 +++++++
 3 files changed, 17 insertions(+), 2 deletions(-)

diff --git a/packages/mermaid/src/config.type.ts b/packages/mermaid/src/config.type.ts
index 79f424315..775d49fb5 100644
--- a/packages/mermaid/src/config.type.ts
+++ b/packages/mermaid/src/config.type.ts
@@ -120,6 +120,13 @@ export interface MermaidConfig {
    *
    */
   legacyMathML?: boolean;
+  /**
+   * This option forces Mermaid to rely on KaTeX's own stylesheet for rendering MathML. Due to differences between OS
+   * fonts and browser's MathML implementation, this option is recommended if consistent rendering is important.
+   * If set to true, ignores legacyMathML.
+   *
+   */
+  forceLegacyMathML?: boolean;
   /**
    * This option controls if the generated ids of nodes in the SVG are
    * generated randomly or based on a seed.
diff --git a/packages/mermaid/src/diagrams/common/common.ts b/packages/mermaid/src/diagrams/common/common.ts
index 017b2b091..364dc25ea 100644
--- a/packages/mermaid/src/diagrams/common/common.ts
+++ b/packages/mermaid/src/diagrams/common/common.ts
@@ -337,11 +337,12 @@ export const renderKatex = async (text: string, config: MermaidConfig): Promise<
     return text;
   }
 
-  if (!isMathMLSupported() && !config.legacyMathML) {
+  if (!(isMathMLSupported() || config.legacyMathML || config.forceLegacyMathML)) {
     return text.replace(katexRegex, 'MathML is unsupported in this environment.');
   }
 
   const { default: katex } = await import('katex');
+  const outputMode = (config.forceLegacyMathML) || (!isMathMLSupported() && config.legacyMathML) ? 'htmlAndMathml' : 'mathml';
   return text
     .split(lineBreakRegex)
     .map((line) =>
@@ -357,7 +358,7 @@ export const renderKatex = async (text: string, config: MermaidConfig): Promise<
         .renderToString(c, {
           throwOnError: true,
           displayMode: true,
-          output: isMathMLSupported() ? 'mathml' : 'htmlAndMathml',
+          output: outputMode
         })
         .replace(/\n/g, ' ')
         .replace(/<annotation.*<\/annotation>/g, '')
diff --git a/packages/mermaid/src/schemas/config.schema.yaml b/packages/mermaid/src/schemas/config.schema.yaml
index d1bb8ad1b..68da484e0 100644
--- a/packages/mermaid/src/schemas/config.schema.yaml
+++ b/packages/mermaid/src/schemas/config.schema.yaml
@@ -180,6 +180,13 @@ properties:
       fall back to legacy rendering for KaTeX.
     type: boolean
     default: false
+  forceLegacyMathML:
+    description: |
+      This option forces Mermaid to rely on KaTeX's own stylesheet for rendering MathML. Due to differences between OS 
+      fonts and browser's MathML implementation, this option is recommended if consistent rendering is important.
+      If set to true, ignores legacyMathML.
+    type: boolean
+    default: false
   deterministicIds:
     description: |
       This option controls if the generated ids of nodes in the SVG are