From f0149722e65a5ccc79a7dfadb3144c7632d1180a Mon Sep 17 00:00:00 2001
From: Mitchell Hashimoto <m@mitchellh.com>
Date: Thu, 5 Sep 2024 14:16:35 -0700
Subject: [PATCH] terminal: add integrity check for unmarked grapheme cell

---
 src/terminal/page.zig | 14 ++++++++++++++
 1 file changed, 14 insertions(+)

diff --git a/src/terminal/page.zig b/src/terminal/page.zig
index 495eb5680..7231550e7 100644
--- a/src/terminal/page.zig
+++ b/src/terminal/page.zig
@@ -289,6 +289,7 @@ pub const Page = struct {
         UnmarkedGraphemeRow,
         MissingGraphemeData,
         InvalidGraphemeCount,
+        UnmarkedGraphemeCell,
         MissingStyle,
         UnmarkedStyleRow,
         MismatchedStyleRef,
@@ -368,6 +369,8 @@ pub const Page = struct {
         var hyperlinks_seen = std.AutoHashMap(hyperlink.Id, usize).init(alloc);
         defer hyperlinks_seen.deinit();
 
+        const grapheme_count = self.graphemeCount();
+
         const rows = self.rows.ptr(self.memory)[0..self.size.rows];
         for (rows, 0..) |*row, y| {
             const graphemes_start = graphemes_seen;
@@ -385,6 +388,17 @@ pub const Page = struct {
                     };
 
                     graphemes_seen += 1;
+                } else if (grapheme_count > 0) {
+                    // It should not have grapheme data if it isn't marked.
+                    // The grapheme_count check above is just an optimization
+                    // to speed up integrity checks.
+                    if (self.lookupGrapheme(cell) != null) {
+                        log.warn(
+                            "page integrity violation y={} x={} cell not marked as grapheme",
+                            .{ y, x },
+                        );
+                        return IntegrityError.UnmarkedGraphemeCell;
+                    }
                 }
 
                 if (cell.style_id != style.default_id) {