terminal: clear spacer heads on growing cols w/o reflow

src/terminal/PageList.zig

@@ -4826,6 +4826,78 @@ test "PageList resize (no reflow) more cols" {
     }
 }
 
+test "PageList resize (no reflow) more cols with spacer head" {
+    const testing = std.testing;
+    const alloc = testing.allocator;
+
+    var s = try init(alloc, 2, 3, 0);
+    defer s.deinit();
+    {
+        try testing.expect(s.pages.first == s.pages.last);
+        const page = &s.pages.first.?.data;
+
+        {
+            const rac = page.getRowAndCell(0, 0);
+            rac.row.wrap = true;
+            rac.cell.* = .{
+                .content_tag = .codepoint,
+                .content = .{ .codepoint = 'x' },
+            };
+        }
+        {
+            const rac = page.getRowAndCell(1, 0);
+            rac.cell.* = .{
+                .content_tag = .codepoint,
+                .content = .{ .codepoint = ' ' },
+                .wide = .spacer_head,
+            };
+        }
+        {
+            const rac = page.getRowAndCell(0, 1);
+            rac.cell.* = .{
+                .content_tag = .codepoint,
+                .content = .{ .codepoint = '😀' },
+                .wide = .wide,
+            };
+        }
+        {
+            const rac = page.getRowAndCell(1, 1);
+            rac.cell.* = .{
+                .content_tag = .codepoint,
+                .content = .{ .codepoint = ' ' },
+                .wide = .spacer_tail,
+            };
+        }
+    }
+
+    // Resize
+    try s.resize(.{ .cols = 3, .reflow = false });
+    try testing.expectEqual(@as(usize, 3), s.cols);
+    try testing.expectEqual(@as(usize, 3), s.totalRows());
+
+    {
+        try testing.expect(s.pages.first == s.pages.last);
+        const page = &s.pages.first.?.data;
+
+        {
+            const rac = page.getRowAndCell(0, 0);
+            try testing.expectEqual(@as(u21, 'x'), rac.cell.content.codepoint);
+            try testing.expectEqual(pagepkg.Cell.Wide.narrow, rac.cell.wide);
+            // try testing.expect(!rac.row.wrap);
+        }
+        {
+            const rac = page.getRowAndCell(1, 0);
+            try testing.expectEqual(@as(u21, ' '), rac.cell.content.codepoint);
+            try testing.expectEqual(pagepkg.Cell.Wide.narrow, rac.cell.wide);
+        }
+        {
+            const rac = page.getRowAndCell(2, 0);
+            try testing.expectEqual(@as(u21, 0), rac.cell.content.codepoint);
+            try testing.expectEqual(pagepkg.Cell.Wide.narrow, rac.cell.wide);
+        }
+    }
+}
+
 // This test is a bit convoluted so I want to explain: what we are trying
 // to verify here is that when we increase cols such that our rows per page
 // shrinks, we don't fragment our rows across many pages because this ends

src/terminal/page.zig

@@ -494,26 +494,34 @@ pub const Page = struct {
         // If we have no managed memory in the row, we can just copy.
         if (!dst_row.grapheme and !dst_row.styled) {
             fastmem.copy(Cell, cells, other_cells);
-            return;
+        } else {
+            // We have managed memory, so we have to do a slower copy to
+            // get all of that right.
+            for (cells, other_cells) |*dst_cell, *src_cell| {
+                dst_cell.* = src_cell.*;
+                if (src_cell.hasGrapheme()) {
+                    // To prevent integrity checks flipping
+                    if (comptime std.debug.runtime_safety) dst_cell.style_id = style.default_id;
+
+                    dst_cell.content_tag = .codepoint; // required for appendGrapheme
+                    const cps = other.lookupGrapheme(src_cell).?;
+                    for (cps) |cp| try self.appendGrapheme(dst_row, dst_cell, cp);
+                }
+                if (src_cell.style_id != style.default_id) {
+                    const other_style = other.styles.lookupId(other.memory, src_cell.style_id).?.*;
+                    const md = try self.styles.upsert(self.memory, other_style);
+                    md.ref += 1;
+                    dst_cell.style_id = md.id;
+                }
+            }
         }
 
-        // We have managed memory, so we have to do a slower copy to
+        // If we are growing columns, then we need to ensure spacer heads
-        // get all of that right.
+        // are cleared.
-        for (cells, other_cells) |*dst_cell, *src_cell| {
+        if (self.size.cols > other.size.cols) {
-            dst_cell.* = src_cell.*;
+            const last = &cells[other.size.cols - 1];
-            if (src_cell.hasGrapheme()) {
+            if (last.wide == .spacer_head) {
-                // To prevent integrity checks flipping
+                last.wide = .narrow;
-                if (comptime std.debug.runtime_safety) dst_cell.style_id = style.default_id;
-
-                dst_cell.content_tag = .codepoint; // required for appendGrapheme
-                const cps = other.lookupGrapheme(src_cell).?;
-                for (cps) |cp| try self.appendGrapheme(dst_row, dst_cell, cp);
-            }
-            if (src_cell.style_id != style.default_id) {
-                const other_style = other.styles.lookupId(other.memory, src_cell.style_id).?.*;
-                const md = try self.styles.upsert(self.memory, other_style);
-                md.ref += 1;
-                dst_cell.style_id = md.id;
             }
         }