terminal: only apply VS15/16 to emoji

Fixes #1482

src/terminal/Terminal.zig

@@ -806,8 +806,12 @@ pub fn print(self: *Terminal, c: u21) !void {
             // If this is an emoji variation selector then we need to modify
             // the cell width accordingly. VS16 makes the character wide and
             // VS15 makes it narrow.
-            //
+            if (c == 0xFE0F or c == 0xFE0E) {
-            // TODO: This should use the emoji-variation-selector.txt UCD file.
+                // This only applies to emoji
+                const prev_props = unicode.getProperties(@intCast(prev.cell.char));
+                const emoji = prev_props.grapheme_boundary_class == .extended_pictographic;
+                if (!emoji) return;
+
                 switch (c) {
                     0xFE0F => wide: {
                         if (prev.cell.attrs.wide) break :wide;
@@ -854,7 +858,8 @@ pub fn print(self: *Terminal, c: u21) !void {
                         break :narrow;
                     },
 
-                else => {},
+                    else => unreachable,
+                }
             }
 
             log.debug("c={x} grapheme attach to x={}", .{ c, prev.x });
@@ -900,6 +905,14 @@ pub fn print(self: *Terminal, c: u21) !void {
             break :prev x - 1;
         };
 
+        // If this is a emoji variation selector, prev must be an emoji
+        if (c == 0xFE0F or c == 0xFE0E) {
+            const prev_cell = row.getCellPtr(prev);
+            const prev_props = unicode.getProperties(@intCast(prev_cell.char));
+            const emoji = prev_props.grapheme_boundary_class == .extended_pictographic;
+            if (!emoji) return;
+        }
+
         try row.attachGrapheme(prev, c);
         return;
     }
@@ -2508,6 +2521,96 @@ test "Terminal: print multicodepoint grapheme, mode 2027" {
     }
 }
 
+test "Terminal: print invalid VS16 non-grapheme" {
+    var t = try init(testing.allocator, 80, 80);
+    defer t.deinit(testing.allocator);
+
+    // https://github.com/mitchellh/ghostty/issues/1482
+    try t.print('x');
+    try t.print(0xFE0F);
+
+    // We should have 2 cells taken up. It is one character but "wide".
+    try testing.expectEqual(@as(usize, 0), t.screen.cursor.y);
+    try testing.expectEqual(@as(usize, 1), t.screen.cursor.x);
+
+    // Assert various properties about our screen to verify
+    // we have all expected cells.
+    const row = t.screen.getRow(.{ .screen = 0 });
+    {
+        const cell = row.getCell(0);
+        try testing.expectEqual(@as(u32, 'x'), cell.char);
+        try testing.expect(!cell.attrs.wide);
+        try testing.expectEqual(@as(usize, 1), row.codepointLen(0));
+    }
+    {
+        const cell = row.getCell(1);
+        try testing.expectEqual(@as(u32, 0), cell.char);
+    }
+}
+
+test "Terminal: print invalid VS16 grapheme" {
+    var t = try init(testing.allocator, 80, 80);
+    defer t.deinit(testing.allocator);
+
+    // Enable grapheme clustering
+    t.modes.set(.grapheme_cluster, true);
+
+    // https://github.com/mitchellh/ghostty/issues/1482
+    try t.print('x');
+    try t.print(0xFE0F);
+
+    // We should have 2 cells taken up. It is one character but "wide".
+    try testing.expectEqual(@as(usize, 0), t.screen.cursor.y);
+    try testing.expectEqual(@as(usize, 1), t.screen.cursor.x);
+
+    // Assert various properties about our screen to verify
+    // we have all expected cells.
+    const row = t.screen.getRow(.{ .screen = 0 });
+    {
+        const cell = row.getCell(0);
+        try testing.expectEqual(@as(u32, 'x'), cell.char);
+        try testing.expect(!cell.attrs.wide);
+        try testing.expectEqual(@as(usize, 1), row.codepointLen(0));
+    }
+    {
+        const cell = row.getCell(1);
+        try testing.expectEqual(@as(u32, 0), cell.char);
+    }
+}
+
+test "Terminal: print invalid VS16 with second char" {
+    var t = try init(testing.allocator, 80, 80);
+    defer t.deinit(testing.allocator);
+
+    // Enable grapheme clustering
+    t.modes.set(.grapheme_cluster, true);
+
+    // https://github.com/mitchellh/ghostty/issues/1482
+    try t.print('x');
+    try t.print(0xFE0F);
+    try t.print('y');
+
+    // We should have 2 cells taken up. It is one character but "wide".
+    try testing.expectEqual(@as(usize, 0), t.screen.cursor.y);
+    try testing.expectEqual(@as(usize, 2), t.screen.cursor.x);
+
+    // Assert various properties about our screen to verify
+    // we have all expected cells.
+    const row = t.screen.getRow(.{ .screen = 0 });
+    {
+        const cell = row.getCell(0);
+        try testing.expectEqual(@as(u32, 'x'), cell.char);
+        try testing.expect(!cell.attrs.wide);
+        try testing.expectEqual(@as(usize, 1), row.codepointLen(0));
+    }
+    {
+        const cell = row.getCell(1);
+        try testing.expectEqual(@as(u32, 'y'), cell.char);
+        try testing.expect(!cell.attrs.wide);
+        try testing.expectEqual(@as(usize, 1), row.codepointLen(0));
+    }
+}
+
 test "Terminal: soft wrap" {
     var t = try init(testing.allocator, 3, 80);
     defer t.deinit(testing.allocator);

src/unicode/main.zig

@@ -4,6 +4,7 @@ const grapheme = @import("grapheme.zig");
 const props = @import("props.zig");
 pub const table = props.table;
 pub const Properties = props.Properties;
+pub const getProperties = props.get;
 pub const graphemeBreak = grapheme.graphemeBreak;
 pub const GraphemeBreakState = grapheme.BreakState;