From fc4eb13e8d16167f2104152ca35b7933146542ca Mon Sep 17 00:00:00 2001
From: Elian Doran <contact@eliandoran.me>
Date: Sat, 5 Apr 2025 09:32:08 +0300
Subject: [PATCH] feat(export/markdown): export display math properly

---
 src/services/export/markdown.spec.ts | 8 +++++++-
 src/services/export/markdown.ts      | 5 +++++
 2 files changed, 12 insertions(+), 1 deletion(-)

diff --git a/src/services/export/markdown.spec.ts b/src/services/export/markdown.spec.ts
index 2726481af..24aa77da2 100644
--- a/src/services/export/markdown.spec.ts
+++ b/src/services/export/markdown.spec.ts
@@ -279,10 +279,16 @@ describe("Markdown export", () => {
         expect(markdownExportService.toMarkdown(html)).toBe(expected);
     });
 
-    it("converts inline math expressions to proper Markdown syntax", () => {
+    it("converts inline math expressions into proper Markdown syntax", () => {
         const html = /*html*/`<p>The equation is&nbsp;<span class="math-tex">\(e=mc^{2}\)</span>.</p>`;
         const expected = `The equation is\u00a0$e=mc^{2}$.`;
         expect(markdownExportService.toMarkdown(html)).toBe(expected);
     });
 
+    it("converts display math expressions into proper Markdown syntax", () => {
+        const html = /*html*/`<span class="math-tex">\[\sqrt{x^{2}+1}\]</span>`;
+        const expected = `$$\sqrt{x^{2}+1}$$`;
+        expect(markdownExportService.toMarkdown(html)).toBe(expected);
+    });
+
 });
diff --git a/src/services/export/markdown.ts b/src/services/export/markdown.ts
index cbc480984..731024435 100644
--- a/src/services/export/markdown.ts
+++ b/src/services/export/markdown.ts
@@ -219,6 +219,11 @@ function buildMathFilter(): Rule {
                 return `$${content.substring(1, content.length - 1)}$`;
             }
 
+            // Display math
+            if (content.startsWith("\\[") && content.endsWith("\\]")) {
+                return `$$${content.substring(2, content.length - 2)}$$`;
+            }
+
             // Unknown.
             return content;
         }