Hello and welcome back! This is Week 6 of my GSoC journey, and I’m excited to share that I’ve finally completed the Dungeon Master engine!
Fixing the Endianness Problem
As I mentioned in the last blog, using READ_LE_UINT16 and WRITE_LE_UINT16 macros had a deeper issue — loadDungeonFile() reads Big-Endian file data and stores it into _thingData as native-endian uint16s, so on a Big-Endian machine the whole setup breaks regardless of the macro fix.
So I spent the first half of this week replacing those byte offset macros by parsing the file data directly into respective arrays of structs at load time. This involved removing all raw byte-to-struct pointer casting (e.g., (Door *)rawDat) from the codebase and updating the file loading and saving routines to read and write fields one at a time using stream operations like readUint16BE and writeUint16BE.
Uncovering Hidden Bugs
These changes also brought some new freezes and crashes to the surface — bugs that were silently hiding behind the old unsafe code. Raw pointer arithmetic was allowing silent reads and writes to out-of-bounds memory, which switching to Common::Array now catches immediately as crashes or assertions. Unsafe casting was hiding cases where one object type was being read as another, which strict C++ type assertions now catch instantly.
Debugging the Endgame
The endgame sequence had quite a few bugs hiding in it. When you capture the Lord of Chaos and fuse him with The Firestaff, the game unlinks the fluxcage — but in fuseSequence(), curThing was never being reset after that, causing the loop to run forever.
When the Lord of Chaos was turned back to normal, the message displayed was also corrupted — wrkString was declared outside the loop so it kept accumulating characters from previous words, and a stray \0 append was preventing it from reading past the first word. Moving wrkString inside the loop and removing \0 fixed the issue.
Another text bug had only the second row showing up in the message area — the first row was being cleared before it could scroll up. createNewRow() was clearing the line buffer before the scroll animation could finish, so the fix was to wait in a small delay loop until _isScrolling is false before proceeding.
Beyond that, I also added support for returning to the launcher after closing the game, along with other small fixes to get the engine to a solid, playable state.
Crash When Renaming Champion in the Hall of Champions
Clicking outside the character select table during champion renaming was calculating an invalid character index from out-of-bounds coordinates, causing a crash. The fix was straightforward — enabling a bounds check that was previously disabled, so clicks outside the table are now simply ignored.
Implementing Extended Saves
I also implemented extended saves for the DM engine, allowing the game to make use of ScummVM’s extended save functionality.
That was it for this week! It’s been a long road getting the DM engine to this point, but it’s rewarding to finally see the work of the previous contributor and Strangerke pay off after 10 years. You can find the previous contributor’s blog here.
Thanks to Sev for helping me throughout this.
I’ll see you in the next blog as I dive into a new engine. Until then, bye! 👋