fix: apply variation selectors to preceding codepoint

src/terminal/Terminal.zig

@@ -377,20 +377,20 @@ pub fn print(self: *Terminal, c: u21) !void {
         // necessarily a grapheme break.
         if (prev.cell.codepoint() == 0) break :grapheme;
 
+        var previous_codepoint: u21 = prev.cell.content.codepoint;
         const grapheme_break = brk: {
             var state: uucode.grapheme.BreakState = .default;
-            var cp1: u21 = prev.cell.content.codepoint;
             if (prev.cell.hasGrapheme()) {
                 const cps = self.screens.active.cursor.page_pin.node.data.lookupGrapheme(prev.cell).?;
                 for (cps) |cp2| {
-                    // log.debug("cp1={x} cp2={x}", .{ cp1, cp2 });
-                    assert(!unicode.graphemeBreak(cp1, cp2, &state));
-                    cp1 = cp2;
+                    // log.debug("cp1={x} cp2={x}", .{ previous_codepoint, cp2 });
+                    assert(!unicode.graphemeBreak(previous_codepoint, cp2, &state));
+                    previous_codepoint = cp2;
                 }
             }
 
-            // log.debug("cp1={x} cp2={x} end", .{ cp1, c });
-            break :brk unicode.graphemeBreak(cp1, c, &state);
+            // log.debug("cp1={x} cp2={x} end", .{ previous_codepoint, c });
+            break :brk unicode.graphemeBreak(previous_codepoint, c, &state);
         };
 
         // If we can NOT break, this means that "c" is part of a grapheme
@@ -402,7 +402,7 @@ pub fn print(self: *Terminal, c: u21) !void {
             // the cell width accordingly. VS16 makes the character wide and
             // VS15 makes it narrow.
             if (c == 0xFE0F or c == 0xFE0E) {
-                const prev_props = unicode.table.get(prev.cell.content.codepoint);
+                const prev_props = unicode.table.get(previous_codepoint);
                 // Check if it is a valid variation sequence in
                 // emoji-variation-sequences.txt, and if not, ignore the char.
                 if (!prev_props.emoji_vs_base) return;
@@ -3318,7 +3318,7 @@ test "Terminal: zero-width character at start" {
     try testing.expect(!t.isDirty(.{ .screen = .{ .x = 0, .y = 0 } }));
 }
 
-// https://github.com/ghostty-org/ghostty/issues/12581
+// https://github.com/ghostty-org/ghostty/pull/12581
 test "Terminal: zero-width character attaches to pending wrap cell" {
     var t = try init(testing.allocator, .{ .cols = 2, .rows = 2 });
     defer t.deinit(testing.allocator);
@@ -3741,6 +3741,27 @@ test "Terminal: invalid VS16 doesn't mark dirty" {
     try testing.expect(!t.isDirty(.{ .screen = .{ .x = 0, .y = 0 } }));
 }
 
+// https://github.com/ghostty-org/ghostty/pull/12596
+test "Terminal: variation selectors apply to preceding codepoint" {
+    var t = try init(testing.allocator, .{ .cols = 5, .rows = 5 });
+    defer t.deinit(testing.allocator);
+
+    // Enable grapheme clustering
+    t.modes.set(.grapheme_cluster, true);
+
+    // Pirate flag: black flag + ZWJ + skull and crossbones + VS16.
+    try t.print(0x1F3F4);
+    try t.print(0x200D);
+    try t.print(0x2620);
+    try t.print(0xFE0F);
+
+    const list_cell = t.screens.active.pages.getCell(.{ .screen = .{ .x = 0, .y = 0 } }).?;
+    const cell = list_cell.cell;
+    try testing.expectEqual(@as(u21, 0x1F3F4), cell.content.codepoint);
+    try testing.expect(cell.hasGrapheme());
+    try testing.expectEqualSlices(u21, &.{ 0x200D, 0x2620, 0xFE0F }, list_cell.node.data.lookupGrapheme(cell).?);
+}
+
 test "Terminal: print multicodepoint grapheme, mode 2027" {
     var t = try init(testing.allocator, .{ .cols = 80, .rows = 80 });
     defer t.deinit(testing.allocator);