terminal/new: pagelist resize to 1 col deletes wide chars

src/terminal/new/PageList.zig

@@ -593,10 +593,6 @@ const ReflowCursor = struct {
         self.y = y;
     }
 
-    fn copyRowMetadata(self: *ReflowCursor, other: *const Row) void {
-        self.page_row.semantic_prompt = other.semantic_prompt;
-    }
-
     fn countTrailingEmptyCells(self: *const ReflowCursor) usize {
         // If the row is wrapped, all empty cells are meaningful.
         if (self.page_row.wrap) return 0;
@@ -614,6 +610,10 @@ const ReflowCursor = struct {
 
         return len;
     }
+
+    fn copyRowMetadata(self: *ReflowCursor, other: *const Row) void {
+        self.page_row.semantic_prompt = other.semantic_prompt;
+    }
 };
 
 /// Reflow the given page into the new capacity. The new capacity can have
@@ -728,6 +728,30 @@ fn reflowPage(
                     dst_cursor.copyRowMetadata(src_cursor.page_row);
                 }
 
+                // A rare edge case. If we're resizing down to 1 column
+                // and the source is a non-narrow character, we reset the
+                // cell to a narrow blank and we skip to the next cell.
+                if (cap.cols == 1 and src_cursor.page_cell.wide != .narrow) {
+                    switch (src_cursor.page_cell.wide) {
+                        .narrow => unreachable,
+
+                        // Wide char, we delete it, reset it to narrow,
+                        // and skip forward.
+                        .wide => {
+                            dst_cursor.page_cell.content.codepoint = 0;
+                            dst_cursor.page_cell.wide = .narrow;
+                            src_cursor.cursorForward();
+                            continue;
+                        },
+
+                        // Skip spacer tails since we should've already
+                        // handled them in the previous cell.
+                        .spacer_tail => {},
+
+                        // TODO: test?
+                        .spacer_head => {},
+                    }
+                } else {
                     switch (src_cursor.page_cell.content_tag) {
                         // These are guaranteed to have no styling data and no
                         // graphemes, a fast path.
@@ -776,6 +800,7 @@ fn reflowPage(
                         dst_md.ref += 1;
                         dst_cursor.page_cell.style_id = dst_md.id;
                     }
+                }
 
                 // If our original cursor was on this page, this x/y then
                 // we need to update to the new location.
@@ -3787,3 +3812,48 @@ test "PageList resize reflow less cols copy style" {
         }
     }
 }
+
+test "PageList resize reflow less cols to eliminate a wide char" {
+    const testing = std.testing;
+    const alloc = testing.allocator;
+
+    var s = try init(alloc, 2, 1, 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.cell.* = .{
+                .content_tag = .codepoint,
+                .content = .{ .codepoint = '😀' },
+                .wide = .wide,
+            };
+        }
+        {
+            const rac = page.getRowAndCell(1, 0);
+            rac.cell.* = .{
+                .content_tag = .codepoint,
+                .content = .{ .codepoint = ' ' },
+                .wide = .spacer_tail,
+            };
+        }
+    }
+
+    // Resize
+    try s.resize(.{ .cols = 1, .reflow = true });
+    try testing.expectEqual(@as(usize, 1), s.cols);
+    try testing.expectEqual(@as(usize, 1), 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, 0), rac.cell.content.codepoint);
+            try testing.expectEqual(pagepkg.Cell.Wide.narrow, rac.cell.wide);
+        }
+    }
+}