Proposal
When placing a new signal (or train station), the action bisects an existing segment, creating a new stop at the cursor and shortening the next stop.The current UX shows you the train length viability at the current stop accurately: I propose the next stop's train length also be displayed
Why
When I make rail systems, especially in space constrained systems like Fulgora, I manually do the forward calculation by putting my finger physically on (just above) my screen where I think I want a new signal, taking my current cursor signal and moving it forward on the rail to see if it will prevent the next stop from being viable with my working train length. If I want to be more precise, I place (and unplace if needed) the signals and then move the cursor, but this is slowed by the time it takes construction bots to travel to the site, which can be far when leveraging remote view with a big base.This UI would allow forward constraints to be seen and placed in one precise hovering preview. I also hope it might help demystify train placement some for new users.
Examples
Rules
This uses the rules, which I believe is an expansion of the current rules with changes in bold and removed existing in- Search for viable stops
signals(before or at) and after the current cursor.
- From the viable stops, calculate back the longest train possible, stopping at the first signal of any kind or train station
- Include any ghosts in the search.
- A viable stop is any train station, or any signal who's segment begins with a train signal, and does not include any train station.
- Display one stop before and one stop after, selecting the stops with the shortest viable train when multiples are available.
Addendum
- Apologies, I misnamed the "Rail Signal" a "Train Signal" and "TS" in the examples document, please read it as such.
- I'm not good a colors. Green, matching the cursor, made sense to me using the current white as the look-ahead, but I have not strong feelings about what these should be. Green may not make as much sense for a hover state (as opposed to placement cursors). There might be a tradeoff between matching the preview color to the hover and construction highlights vs having one consistent preview color across both experiences. It's hard to tell without seeing the colors in game rather than with crappy edited screenshots.
- I do think the signals associated with a train preview should all be highlighted in the same colors as the preview
- I understand adding ghosts may not be a viable, for practical purposes I think this still works if only the current cursor is considered. I also think would be a huge boon if it worked with already placed ghosts, as otherwise the preview is inaccurate until the ghosts are reified, but this is already true in the game today.
- Train Stations are signals and don't create segments, but they are always a spot a train can stop, and I think they should be considered in these calculation.
- I haven't played much with how multiple paths before and after might look in this preview, there may be some non-intuitive edge cases I haven't considered, but I believe the "show shortest train from the options" rule displays the most relevant information for designing a rail circuit with enough room to accommodate the players choice of train size.

