OpenLoco v23.12 is out! With the winter holidays getting closer, we thought we’d treat you to an early release this month! It’s mostly bugfixes this month, but there’s also been some interesting work behind the scenes, as usual.

We hope you’ll enjoy reading this dev log, and will take the new release for a spin as well, between what will hopefully be a nice holiday period for you and your loved ones. From us in the OpenLoco team: Happy Holidays!

Enable extra optimizations for Windows release builds (#2204)

While working on our sister project OpenRCT2, @ZehMatt noticed some of the optimizations he applied there could also be applied to OpenLoco. As it turns out, particular compiler intrinsics were not enabled, which meant that direct memory writes were disabled and memcpy calls were used instead. In addition, the linker wasn’t eliminating unreferenced data and code, nor were identical functions merged. Enabling the right intrinsics for the MSVC compiler shrinks the OpenLoco binary by as much as 300 KiB, and has decreased the amount of functions from 10,195 down to 6,899. As @ZehMatt puts it, free code and size optimizations, basically. Yay!

Fix crash when clipping strings (#2207)

A few months ago, we changed how strings were processed in game. This unexpectedly led to crashes in some places in the game. What happened?

While games nowadays have happily adopted Unicode for most of their text strings (e.g. through UTF-8), OpenLoco, like Locomotion, currently uses a dialect of the ISO 8859-1 code page to present text to the player. We say it’s a dialect, because some code points defined in this standard are used for other purposes, such as the icons for stations you see in labels, or as formatting codes, e.g. text colours. Dealing with these can be a bit delicate, and until we’ve reimplemented every function that deals with strings, we’ve got to keep it as-is.

Turns out there’s a mysterious formatting code at the start of company names, 0x90 in hexadecimal. Our code was tripping over this particular byte, leading to the crash. Hopefully, we can get rid of the hack that solved it soon.

Fix landscape generator not taking town size limits into account (#2209)

In July, we merged our implementation of the createTown game command. What we didn’t notice in the review process, is that the town size limit wasn’t being passed properly, leading to an unexpected abundance of metropoles on maps that were expecting small towns only! Fortunately, the issue was identified and resolved quickly after it was reported – though it took a while to discover, it seems!

Implement track/road ordering functions, and PaintSession refactor (#2216, #2218)

We’re expanding our efforts again, this time into what we call the paint part of the game. As many of you know, the game uses prerendered sprites for showing landscapes, vehicles etc. on the game canvas. The functions that map game data onto these sprites, are what we call paint functions.

This month, @duncanspumpkin implement the paint functions that reorder the track and road sprites to draw them properly. The nice thing is that our implementation of these functions can be written to be much more compact than the originals. We hope that this will not only leave them to be more readable, but to lead to faster performance eventually as well.

Later in the same week, @ZehMatt then took the opportunity to refactor the PaintSession to bundle variables and improve readability. Loads more to do, but we’re chipping away at these!

Fix behavioural divergence regressions from v23.10 (#2217)

We use replay tests to try to ensure we don’t break any vanilla game logic while we reimplement the game’s functions one-by-one. Unfortunately, we missed a few regressions caused by recent C++ implementations of some of the vehicle logic. Thankfully, @duncanspumpkin discovered and identified the issues, and they are fixed now.

Fix cursor resetting when the game auto saves (#2223)

During testing, @ZehMatt noticed that the game triggering an auto save would reset the cursor to a regular pointer, rather than the cursor for whatever tool might have been active. Nothing game-breaking, but a good thing to have fixed!

Fix route-through order assignments (#2200)

Assigning vehicles an order to stop at a particular station is simple: you just click their label once. Clicking it twice will order the vehicle to route through the station instead. Or does it? It turned out our implementation of assigning such route-through orders worked differently from vanilla. @duncanspumpkin worked out that, while vanilla’s worked on the previous order, ours would work on the highlighted order instead. Given that assigning an order automatically moves the selected order forward by one, we would always be off by one, breaking this double-clicking behaviour! Glad to have this one fixed as well.

Mouse wheel input refactor (#2225)

Rapidly zooming in and out of the map led to some jittery scrolling behaviour, @ZehMatt found. This led him to identify and fix an underlying bug, and clean up the code a little in the process. Nice work!