HKR Split-Flap Display

A split-flap-display style MTR PIDS resource pack for JCM (Joban Client Mod) — a recreation of the flip display on the Hana-Koshi Line on the official MTR server.

In-game screenshot (three service types on one screen — note the split-flap seams, the per-service badge colours and the line diagram):

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Origin & Credits

This pack recreates the split-flap display found on the Hana-Koshi Line (花越线) platforms, built by Forest_E233 on the official MTR server (MTR Let's Play).

• Server wiki: https://wiki.minecrafttransitrailway.com/zh:mtr_letsplay:start
• The original screen is 3:2
• Joban Client Mod's PIDS canvas is 2:1 (136 × 76 design units)

Because of the different aspect ratio, the layout differs slightly. Elements had to be re-arranged for the 2:1 canvas; font sizes, row heights, baselines and badge widths in this pack were calibrated item by item against reference screenshots so that the 2:1 rendering stays as close as possible to the 3:2 original.

MTR and Joban Client Mod are the work of their respective authors. This project is not affiliated with either of them.

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Installation

1. Download HKR-Split-Flap-Display.zip from Releases and drop it into .minecraft/resourcepacks/ (do not unzip, and do not leave an extra folder level inside)
2. Enable it in Options → Resource Packs
3. Place a JCM PIDS block, right-click it, and under Custom PIDS Option choose HKR Split-Flap Display
4. After editing script settings, press F3 + T to reload the pack

Supported blocks

Only JCM's PIDS blocks are supported:

jsblock:rv_pids, rv_pids_sil_1, rv_pids_sil_2, lcd_pids, pids_projector, pids_1a

MTR's built-in mtr:pids_1 … pids_4 will NOT work — those blocks don't support scripted presets.

Requirements

Mod	Version
Minecraft	1.19.4 – 1.21
Minecraft Transit Railway (MTR)	4.x
Joban Client Mod (JCM)	2.x

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What it displays

Area	Content
Title	下班車 Next Train
種別 Type	Service-type badge (Chinese + English), colour-coded per service
目的地 Destination	Terminus name (bilingual), from MTR data
月台 Plat.	Platform-number circle, tinted with the MTR route colour
開出 Dep. Time	Under 10 minutes: countdown N 分鐘; 10 minutes or more: real-world clock xx:xx
停靠站 Stopping at	Full line diagram: grey dot = not served, lit white = served, breathing light on the terminus, large dot on the current station
第二班 / 第三班	The next two trains

Split-flap details

The reference is a split-flap display, so this pack reproduces its visual traits:

• Centre seam — a thin dark horizontal line through the middle of every cell (measured pixel by pixel from the 00:18 digits in the reference)
• Flip animation — when the content changes, the top flap falls while the bottom half stays put, exactly like a real split-flap unit
• Flip sound — a "clack" on each flip, positionally attenuated and globally rate-limited

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Route number / service type reference

This is the part you will most likely want to change. The badge text and colour come from the SERVICE_OVERRIDE table at the top of assets/jsblock/scripts/next_train.js.

Recommended MTR route naming

MTR route names use the format Chinese|English, and a double pipe || marks a note. Put the service type in the route name or route number and the script picks it up:

Type	中文	English	Badge colour	Suggested route name / number	Matched keywords
特急	特急	Spec.press	#D32F2F red	特急|Spec.press	特急
準急	準急	Semi Exp.	#27AE60 green	準急|Semi Exp.	準急, Semi Exp.
特快	特快	Special Rapid	#453EA5 purple	特快|Special Rapid	特快
通快	通快	Com.Rapid	#0E9E9E teal	通快|Com.Rapid	通快, Com.Rapid
急行	急行	Ex.press	#E67E22 orange	急行|Ex.press	急行, Ex.press
快速	快速	Rapid	#215DB3 blue	快速|Rapid	快速
各停	各停	Local	#3C3C3C grey	各停|Local	各停

Put it in the route number

The service type is read from MTR's "route number" only, so the values above go in the Route Number field. Whatever the route name says is irrelevant (test, empty, anything).

• If the route number is empty, the script falls back to the route name so the badge never goes blank
• A || note works inside the number too → 花越线|Hana Line||特急|Spec.press
• Direction words are ignored automatically → 快速|Rapid||上行 still shows "快速 Rapid" (direction is meaningless on a PIDS: which platform you are on already determines it)

Earlier versions tried to auto-detect whether the name or the number "looked more like a service type". That is gone — the route number is now the single source, so the behaviour is predictable and can't be thrown off by an unrelated word in the name.

Custom mapping table

If you don't want to depend on MTR naming, hard-code it in the script:

const SERVICE_OVERRIDE = [
    { name: ["特急"],                color: "D32F2F" },  // red
    { name: ["準急", "Semi Exp."],   color: "27AE60" },  // green
    { name: ["特快"],                color: "453EA5" },  // purple
    { name: ["通快", "Com.Rapid"],   color: "0E9E9E" },  // teal
    { name: ["急行", "Ex.press"],    color: "E67E22" },  // orange
    { name: ["快速"],                color: "215DB3" },  // blue
    { name: ["各停"],                color: "3C3C3C" }   // grey

    // Match by route number
    // { number: "507", zh: "各停", en: "Local", color: "00A650" },
    // Hard-code the text too
    // { name: ["普通"], zh: "普通", en: "Ordinary", color: "7F8C8D" }
];

• Matched top to bottom, first hit wins (put more specific entries first)
• name may be a string or an array; any element matching counts as a hit
• number must match the route number exactly
• If you only set color, the badge text still comes from the route name / || note

How to set up express services in MTR

MTR has no concept of "local vs express". An express service is simply a separate route with a different platform list:

1. Create a separate route for "Rapid"
2. Add only the platforms it stops at — the ones you leave out are passed through
3. Skipped stations show up as grey dots on the line diagram

Route	Platforms	Line diagram
各停 Local	all 11	every dot lit white
快速 Rapid	only 6	the 5 skipped stations are grey
特急 Spec.press	only 4	the 7 skipped stations are grey

Grey vs. white is determined entirely by that route's platform list — no script changes needed.

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Customisation

Every tunable lives at the top of the script, in this order:

Setting	Purpose
SS	Supersampling factor (default 8 → 1088×608 texture)
C_*	Full colour palette
SERVICE_OVERRIDE	Service-type mapping table (see above)
SERVICE_IGNORE_EXTRA	Direction words to ignore
BADGE_*	Badge width, font size, wrapping, italics
LABELS	Every hard-coded string on screen
COUNTDOWN_WITHIN_MINUTES	Countdown / clock threshold (default 10 minutes)
TIME_SOURCE	Base time on arrival or departure
SEAM_*	Split-flap seams
FLIP_*	Flip animation and sound
TERMINAL_LED_*	Terminus breathing light
STOP_BLINK_*	Stopping-station white light
CURRENT_STATION_MARK	Draw a large dot on the current station
BAR_COLOR_FROM / PLATFORM_COLOR_FROM	Which colour the line bar / platform circle uses
L	The whole layout geometry
F_CJK / F_LATIN / F_MONO	Font families

Hard-coded strings on screen

Titles, column headers and the second/third-train labels all live in LABELS:

const LABELS = {
    title:       { zh: "下班車",       en: "Next Train" },
    type:        { zh: "種別",         en: "Type" },
    destination: { zh: "目的地",       en: "Destination" },
    platform:    { zh: "月台",         en: "Plat." },
    depTime:     { zh: "開出",         en: "Dep. Time" },
    stoppingAt:  { zh: "停靠站",       en: "Stopping at" },
    secondTrain: { zh: "第二班",       en: "Second train" },
    thirdTrain:  { zh: "第三班",       en: "Third train" },
    noService:   { zh: "暫無列車資訊", en: "No train information" }
};

Set the en value to an empty string "" to show Chinese only.

Performance

• Texture is 1088×608 by default (SS = 8)
• The script skips redrawing and re-uploading when nothing changed — a PIDS only changes about once per second
• Animated effects (the terminus light) quantise their phase into 10 steps, so the texture is re-uploaded ~9 times per second instead of 60
• Drop SS to 4 if it's too heavy; raise it to 10 / 12 for more sharpness

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File structure

HKR-Split-Flap-Display/
├── pack.mcmeta
├── LICENSE                             # MIT
├── NOTICE.md                           # third-party attribution
├── pack.png
├── preview.png
├── screenshots/ingame.png              # in-game screenshot
└── assets/jsblock/
    ├── joban_custom_resources.json      # preset registration
    ├── scripts/next_train.js            # all rendering logic
    └── textures/pids/next_train/
        └── thumbnail.png                # thumbnail in the preset picker

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Hacking on it: five Rhino gotchas in JCM

The script runs on the Rhino 1.9.1 engine embedded in JCM, which differs from browser/Node JavaScript in several ways. Read these before editing:

1. Never use const inside a loop body

Rhino treats block-level const as function-scoped and does not re-initialise it on each iteration. A const inside a for loop silently keeps the first iteration's value:

// ✗ splitRuns("Next Train") returns "NNNNNNNNNN"
for (var i = 0; i < s.length; i++) { const c = s.charAt(i); ... }

// ✓ use var
for (var i = 0; i < s.length; i++) { var c = s.charAt(i); ... }

That's why every function body in this pack uses var (top-level config still uses const).

2. No duplicate names inside one function

Rhino does function-level duplicate checks for block-level let / const. Declaring const x in both branches of an if/else fails outright with redefinition or conflict of variable "x". Use distinct names.

3. Don't use new Color(r, g, b)

java.awt.Color has both Color(int,int,int) and Color(float,float,float); Rhino picks the float overload → IllegalArgumentException. Use the single-arg form:

new Color((r << 16) | (g << 8) | b)   // ✓

Same ambiguity for Font.deriveFont(int style) vs deriveFont(float size) — always use the two-arg form deriveFont(style, size).

4. Don't use Font.deriveFont(ITALIC) for italics

JCM's Resources.getSystemFont() returns fonts loaded via Font.createFont, which are not in the system font registry, so deriveFont(ITALIC) is unreliable. This pack implements italics with g.shear(-0.21, 0) plus an x compensation.

5. Sound positions are relative

The docs for PIDSScriptContext.getSoundManager() say "The base position are set to the block's position", and the pos argument of playSound(id, pos, ...) is relative to that base position. So pass the zero vector new Vector3f(0, 0, 0) (i.e. sound at the block). Passing an absolute position such as pids.blockPos() puts the source at twice the coordinates — completely out of earshot.

What happens on error

A script crash does not produce a black screen; it renders PIDS script error plus the message, so you can read the problem in-game.

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How this was verified

Every change went through these layers:

Layer	What is checked
Structure	pack.mcmeta / preset JSON / script paths agree; parentheses balanced
Static	No const/let shadowing, no multi-arg Color, no single-arg deriveFont
Real Rhino	create/render/dispose executed on actual Rhino 1.9.1 + real java.awt
Boundaries	no arrivals, no route data, LCD 133×72, PIDS 1A 90×46, single train, 40×20 small, 272×152 large
Behaviour	service-type parsing, line caching, flip direction, current-station marker, flip sound
Rendering	frame-by-frame simulation rendering, error screens forbidden

Dynamic behaviour such as the flip animation and the terminus light is verified pixel by pixel, not eyeballed:

• Flip: an assertion test guarantees "the bottom half must not move until the flap lands"
• Terminus light: per-phase sampling proves "radius constant, only colour moves grey↔white"

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Contributors

• ChihayaAnonQWQ — requirements, reference material, testing, and the repeated refinement of colours and layout
• DeepSeek — script implementation, layout calibration, verification tooling

License

MIT

The layout design references the Hana-Koshi Line split-flap display built by Forest_E233 on the official MTR server, for study and personal use. MTR and Joban Client Mod remain the property of their respective authors.

See NOTICE.md for third-party attribution.