ignore zero-width characters for now

src/terminal/Screen.zig

@@ -63,8 +63,7 @@ pub const Cell = struct {
     bg: ?color.RGB = null,
 
     /// On/off attributes that can be set
-    /// TODO: pack it
-    attrs: struct {
+    attrs: packed struct {
         bold: u1 = 0,
         underline: u1 = 0,
         inverse: u1 = 0,
@@ -82,12 +81,22 @@ pub const Cell = struct {
         /// wide character (tail) or following (head).
         wide_spacer_tail: u1 = 0,
         wide_spacer_head: u1 = 0,
+
+        _padding: u1 = 0,
     } = .{},
 
     /// True if the cell should be skipped for drawing
     pub fn empty(self: Cell) bool {
         return self.char == 0;
     }
+
+    test {
+        // We use this test to ensure we always get the right size of the attrs
+        const cell: Cell = .{ .char = 0 };
+        try std.testing.expectEqual(1, @sizeOf(@TypeOf(cell.attrs)));
+
+        log.warn("CELL={}", .{@sizeOf(Cell)});
+    }
 };
 
 pub const RowIterator = struct {

src/terminal/Terminal.zig

@@ -346,7 +346,11 @@ pub fn print(self: *Terminal, c: u21) !void {
     // Determine the width of this character so we can handle
     // non-single-width characters properly.
     const width = utf8proc.charwidth(c);
-    assert(width == 1 or width == 2);
+    assert(width <= 2);
+
+    // For now, we ignore zero-width characters. When we support ligatures,
+    // this will have to change.
+    if (width == 0) return;
 
     // If we're soft-wrapping, then handle that first.
     if (self.screen.cursor.pending_wrap and self.modes.autowrap == 1)