For Google Summer of Code 2025, I worked on GNOME Crosswords. GNOME Crosswords is a project that consists of two apps:

• Crosswords, a crossword player
• Crossword Editor, a crossword editor.

Links

Here are links to everything that I worked on.

Merge requests

Merge requests related to the word suggestion algorithm:

1. Improve word suggestion algorithm
2. Add word-list-tests-utils.c
3. Refactor clue-matches-tests.c by using a fixture
4. Use better test assert macros
5. Add macro to reduce boilerplate code in clue-matches-tests.c
6. Add a macro to simplify the test_clue_matches calls
7. Add more tests to clue-matches-tests.c
8. Use string parameter in macro function
9. Add performance tests to clue-matches-tests.c
10. Make phase 3 of word_list_find_intersection() optional
11. Improve print functions for WordArray and WordSet

Other merge requests:

Over the past few weeks, I’ve been working on improving some test code that I had written.

Refactoring time!

My first order of business was to refactor the test code. There was a lot of boilerplate, which made it difficult to add new tests, and also created visual clutter.

For example, have a look at this test case:

static void
test_egg_ipuz (void)
{
  g_autoptr (WordList) word_list = NULL;
  IpuzGrid *grid;
  g_autofree IpuzClue *clue = NULL;
  g_autoptr (WordArray) clue_matches = NULL;

  word_list = get_broda_word_list ();
  grid = create_grid (EGG_IPUZ_FILE_PATH);
  clue = get_clue (grid, IPUZ_CLUE_DIRECTION_ACROSS, 2);
  clue_matches = word_list_find_clue_matches (word_list, clue, grid);

  g_assert_cmpint (word_array_len (clue_matches), ==, 3);
  g_assert_cmpstr (word_list_get_indexed_word (word_list,
                                word_array_index (clue_matches, 0)),
                   ==,
                   "EGGS");
  g_assert_cmpstr (
    word_list_get_indexed_word (word_list,
                                word_array_index (clue_matches, 1)),
    ==,
    "EGGO");
  g_assert_cmpstr (
    word_list_get_indexed_word (word_list,
                                word_array_index (clue_matches, 2)),
    ==,
    "EGGY");
}

That’s an awful lot of code just to say:

In the past few weeks, I’ve been working on the MR for my lookahead algorithm. And now, it’s finally merged! There’s still some more work to be done—particularly around the testing code—but the core change is finished, and is live.

Suboptimal code?

While working on my MR, I noticed that one of my functions, word_set_remove_unique (), could be optimized. Here is the function:

void
word_set_remove_unique (WordSet *word_set1, WordSet *word_set2)
{
  g_hash_table_foreach_steal (word_set1, word_not_in_set, word_set2);
}

/* Helper function */
static gboolean word_not_in_set (gpointer key,
                                 gpointer value,
                                 gpointer user_data)
{
  WordIndex *word_index = (WordIndex *) key;
  WordSet *word_set = (WordSet *) user_data;
  return !g_hash_table_contains (word_set, word_index);
}

word_set_remove_unique () takes two sets and removes any elements in the first set that don’t exist in the second set. So essentially, it performs a set intersection, in-place, on the first set.

In the last two weeks, I’ve been working on my lookahead-based word suggestion algorithm. And it’s finally functional! There’s still a lot more work to be done, but it’s great to see that the original problem I set out to solve is now solved by my new algorithm.

Without my changes

Here’s what the upstream Crosswords Editor looks like, with a problematic grid:

The editor suggests words like WORD and WORM, for the 4-Across slot. But none of the suggestions are valid, because the grid is actually unfillable. This means that there are no possible word suggestions for the grid.

In the last two weeks, I investigated some bugs, tested some fonts, and started working on a design doc.

Bugs

I found two more UI-related bugs (1, 2). These are in addition to the ones I mentioned in my last blog post—and they’re all related. They have to do with GTK and sidebars and resizing.

I looked into them briefly, but in the end, my mentor decided that the bugs are complicated enough that he should handle them himself. His fix was to replace all the .ui files with Blueprint files, and then make changes from there to squash all the bugs. The port to Blueprint also makes it much easier to edit the UI in the future.

In the last two weeks, I did three things:

• Fixed a rebus bug.
• Combined the two suggested words lists into one.
• Found some more bugs.

The rebus bug

A rebus cell is a cell that contains more than one letter in it. These aren’t too common in crossword puzzles, but they do appear occasionally—and especially so in harder puzzles.

Our word suggestions lists were not working for slots with rebus cells. More specifically, if the cursor was on a cell that’s within letters in rebus - 1 cells to the right of a rebus cell, then an assertion would fail, and the word suggestions list would be empty.

In the last two weeks, I’ve been trying to fix a strange bug that causes the word suggestions list to have the wrong order sometimes.

For example, suppose you have an empty 3x3 grid. Now suppose that you move your cursor to each of the cells of the 1-Across slot (labelled α, β, and γ).

+---+---+---+
| α | β | γ |
+---+---+---+
|   |   |   |
+---+---+---+
|   |   |   |
+---+---+---+

You should expect the word suggestions list for 1-Across to stay the same, regardless of which cell your cursor is on. After all, all three cells have the same information: that the 1-Across slot is empty, and the intersecting vertical slot of whatever cell we’re on (1-Down, 2-Down, or 3-Down) is also empty.

Today marks the end of the community bonding period, and the start of the coding period, of GSoC.

In the last two weeks, I’ve been looking into other crossword editors that are on the market, in order to see what features they have that we should implement.

I found the process enlightening. It was interesting to try so many different versions of the same product. The UIs differ quite dramatically, the same feature may be implemented differently in each editor, and some features only exist in a few or even a single editor.

I will be contributing to GNOME Crosswords, as part of the Google Summer of Code 2025 program. My project adds construction aids to the Crosswords editor. These aids provide hints, warnings, and data that help the user create better crossword puzzles.

I have three mentors:

• Jonathan Blandford
• Federico Mena Quintero
• Tanmay Patil

GNOME Crosswords

The GNOME Crosswords project consists of two applications:

• The Crosswords player, which lets you play crossword puzzles.
• The Crosswords editor, which lets you create crossword puzzles.

My project focuses on the Crosswords editor.