LineChart

Jetpack Compose trading chart with candles, 30 indicators, multi-pane layout, live updates and marketplace components, plus a pure Kotlin order book engine.

Features

• Candle, Line and Area series (ChartType) with volume, a last price line and visible-range high/low markers
• 9 overlay and 21 pane indicators, multi-pane layout with per-pane axes, legends and crosshair tags
• Pan with fling, pinch zoom, long-press crosshair, long-press pane resize; vertical drags go to the parent scroll
• Real-time updates that keep the viewport, zoom and crosshair and follow the right edge
• Log and percent price scales, left or right axis, grid modes, base lines, price limits, font scale (ChartSettings)
• Timeframes from tick to year with aggregate
• Korean (red up, blue down) and International (green up, red down) palettes with dark variants, or a custom ChartColors
• English and Korean labels
• Market components (depth chart, order book ladder, trade list, option selector, instant trade buttons) and linechart-orderbook, a deterministic matching engine

Installation

dependencies {
    implementation("io.github.teddko:linechart:1.1.1")
    // optional, pure Kotlin matching engine for marketplace screens
    implementation("io.github.teddko:linechart-orderbook:1.1.1")
}

Requirements:

• minSdk 23, compileSdk 37 or newer
• Kotlin 2.2 or newer (stdlib 2.2.21)
• Compose ui and foundation 1.12.1 or newer
• linechart-orderbook needs only the Kotlin stdlib and runs on any JVM

The linechart POM lists only Compose ui, foundation and kotlin-stdlib, material3 is not a dependency. The linechart-orderbook javadoc jar is empty, which Maven Central accepts; Dokka may follow later.

Quick start

val state = rememberLineChartState(items)

LineChartPanel(
    modifier = Modifier.fillMaxWidth(),
    state = state,
    chartType = ChartType.Candle,
    colors = ChartColors.Korean,
    overlays = listOf(MovingAverage(), BollingerBands()),
    panes = listOf(Volume(), Rsi(), Macd()),
    settings = ChartSettings(scale = PriceScale.Linear),
    timeframe = Timeframe.Minute5,
)

ChartData(cumulativeProfit, date, open, high, low, volume, value) carries one sample:

• cumulativeProfit is the line value and the candle close
• date is epoch millis and the identity of the sample
• open, high and low default to the close
• volume and value default to 0; value is the traded value used by TradingValue, which falls back to close times volume when it is 0

LineChartPanel and LineChart keep their 1.0 signatures through hidden shims. Defaults are chartType = Candle, overlays = listOf(MovingAverage()), panes = listOf(Volume()), settings = ChartSettings(), paneHeight = 80.dp.

Chart types and palettes

ChartType	Drawing
Candle	Body 70 percent of the slot, wick high to low, direction color; below 3 px only the wick
Line	Smooth line split at a reference price: up color above, down color below; pulse on the last point in the color of its side
Area	Line with a vertical gradient fill, split the same way

The reference of Line and Area is the base line value (ChartSettings.baseLine), else the previous session close, else the first visible close. An intraday series without a previous day therefore compares against the first visible close.

Palette	Up	Down
ChartColors.Korean (default)	red	blue
ChartColors.International	green	red
ChartColors.KoreanDark, ChartColors.InternationalDark	dark-surface variants

The default follows isSystemInDarkTheme(). Indicator colors are constructor parameters; direction and sign colors resolve from ChartColors.

Any up and down colors work:

LineChartPanel(state = state, colors = ChartColors(up = Color(0xFFFF6A00), down = Color(0xFF7B61FF)))

The demo settings end every color row with a color wheel: angle picks the hue, distance from the center the saturation, and a slider the value.

Timeframes and aggregate

Timeframe is a unit with a count: Tick, Second1/5/10/30, Minute1/3/5/10/15/30/60/120/240, Day, Week, Month, Year, or Timeframe(TimeframeUnit.Minute, 7). Second and minute counts align per day from local midnight, so any count works.

val candles = ticks.aggregate(Timeframe.Minute5)

aggregate builds candles (first open, max high, min low, last close, summed volume and value, bucket start date) in the device time zone, weeks starting Monday. A Tick group takes the date of its first item, so a growing last group keeps its identity. aggregate(timeframe, timeZone) takes the zone for the buckets. The input must be in time order.

• timeframe on the panel only labels the axis and legends; it does not aggregate
• Indicator periods count candles of the current timeframe, so MA5 on a weekly chart is five weeks, and the legend shows the unit (MA5D, MA20분)
• Time axis patterns: HH:mm:ss for tick and second, HH:mm for minute, MM/dd for day and week, yyyy/MM for month, yyyy for year. An intraday label turns into MM/dd at the first candle of a new day and wherever the label stride spans a day or more
• The crosshair time tag uses the full date for the timeframe
• Aggregating the full list on every tick suits modest histories; with a large history keep the aggregated list and re-aggregate only the last bucket
• To show another zone pass timeFormatter, for example { millis -> format.format(Date(millis)) } with a SimpleDateFormat whose timeZone is set
• Adjusted prices (splits, dividends) are the app's responsibility: the library has no corporate-action data, so pass adjusted data

Gestures

Gesture	Result
Horizontal drag	Pan, with fling
Two-finger pinch	Zoom around the fingers
Long press, then drag	Crosshair with price and time tags across all panes, the legends follow the item under it; hides on release
Long press within 12dp of a separator, then drag	Resizes the panes: haptic tick, highlighted separator, the area above grows and the one below shrinks by the same amount
Vertical drag	Passed to the parent scroll

Indicators

Pass overlays = listOf(...) for the main pane and panes = listOf(...) for the area below it. Indicators compare by value, weight scales a pane height, warm-up values are not drawn, and n < period never throws. Indicators that need volume (Vwap, VolumeProfile, Volume, TradingValue, Obv, Mfi, VolumeRatio, VolumeOscillator) are hidden while the series has no volume. Price source is the close.

Overlays

Notation: c close, h high, l low, v volume, tp = (h + l + c) / 3.

Class	Defaults	Formula
MovingAverage(periods, type, colors, widths, visible)	5, 20, 60, 120, Simple	SMA Σc/n; EMA α = 2/(n+1) seeded by SMA(n); WMA Σk·c/Σk (MaType)
BollingerBands(period, k)	20, 2.0	SMA ± k·σ (population)
Envelope(period, percent)	20, 6	SMA·(1 ± p/100)
Ichimoku(conversion, base, span, shift)	9, 26, 52, 26	conversion (HH9+LL9)/2, base (HH26+LL26)/2, span 1 (conversion+base)/2 and span 2 (HH52+LL52)/2 both shifted forward by shift−1, lagging c shifted back by shift−1
ParabolicSar(step, max)	0.02, 0.2	Wilder SAR, initial trend from sign(c1−c0), dots below in an uptrend and above in a downtrend
PriceChannel(period)	20	max h and min l of the previous n bars, current excluded
Pivot()	none	previous local day H/L/C (previous candle for day and longer): P = tp, R1 = 2P−L, S1 = 2P−H, R2 = P+(H−L), S2 = P−(H−L)
Vwap()	none	Σ(tp·v)/Σv, reset per local day for intraday, cumulative for day and longer
VolumeProfile(bins)	10	the visible range split into bins, each candle volume into the bin of its close, left aligned bars up to 30 percent of the width, the largest bin marked

Panes

Class	Defaults	Formula	Scale and levels
Volume(maPeriods)	MA 5, 20	v and SMA(v)	0 to max
TradingValue(maPeriods)	MA 5, 20	value when above 0, else c·v	0 to max
Macd(fast, slow, signal)	12, 26, 9	EMA12−EMA26, signal EMA9, histogram macd−signal	around 0
MacdOscillator(fast, slow, signal)	12, 26, 9	histogram only	around 0
Rsi(period, signal)	14, 6	Wilder RS, signal SMA	0 to 100; 30, 70
StochasticFast(k, d)	5, 3	%K = 100(c−LLk)/(HHk−LLk), 50 when flat; %D = SMA	0 to 100; 20, 80
StochasticSlow(k, smooth, d)	5, 3, 3	slow K = SMA(fast K, smooth), slow D = SMA(slow K, d)	0 to 100; 20, 80
WilliamsR(period)	14	−100(HH−c)/(HH−LL)	−100 to 0; −20, −80
Cci(period)	20	(tp−SMA(tp))/(0.015·mean absolute deviation)	auto including ±100; ±100
Dmi(period, adx)	14, 14	Wilder +DM, −DM, TR; ±DI; DX; ADX = Wilder(DX)	auto from 0
Atr(period)	14	Wilder of max(h−l, abs(h−c₋₁), abs(l−c₋₁))	auto
Obv(signal)	9	cumulative ±v by sign(c−c₋₁), signal SMA	auto
Mfi(period)	14	positive and negative money flow of tp·v by tp versus tp₋₁	0 to 100; 20, 80
Momentum(period, signal)	10, 9	100·c/c₋ₙ, signal SMA	auto around 100; 100
Roc(period)	12	100(c−c₋ₙ)/c₋ₙ	around 0; 0
Trix(period, signal)	12, 9	E3 = EMA³(c), 100(E3−E3₋₁)/E3₋₁, signal SMA	around 0
Disparity(periods)	20, 60	100·c/SMA(n)	auto around 100; 100
Psychological(period)	10	100·count(c > c₋₁ in the last n)/n	0 to 100; 25, 75
VolumeRatio(period)	20	100(ΣVup + ΣVflat/2)/(ΣVdown + ΣVflat/2)	auto; 70, 450
VolumeOscillator(short, long)	5, 20	100(EMA5(v)−EMA20(v))/EMA20(v)	around 0
Sonar(period, lag, signal)	20, 9, 9	100(EMAn−EMAn₋ₘ)/EMAn₋ₘ with m = lag, signal SMA	around 0

Notes:

• RSI uses Wilder smoothing; the 14-period reference series gives 70.46 at its first full value
• The slow stochastic defaults to 5, 3, 3
• Sonar has no single definition: brokers differ in the base average and the lag. This formula is EMA momentum, check it against the broker you compare with
• A division by zero (for example Roc across a zero close) draws a gap and shows - in the legend, never infinity
• Ichimoku extends the chart to the right by shift−1 candle slots (25 by default), and the cloud is filled up-colored where span 1 ≥ span 2, down-colored otherwise
• Oscillator values and tags use two decimals with Locale.ROOT; volume-type panes use K, M and B suffixes

Excluded: AB ratio, ADL, CMF, Chaikin, NCO, Stochastic RSI, Keltner, SuperTrend, Heikin-Ashi.

Main Y range

The main pane range is the visible low and high with 5 percent padding. Bollinger, Envelope, PriceChannel, Ichimoku (spans and cloud), ParabolicSar and Vwap are included in it. MovingAverage, Pivot and VolumeProfile are not, and are clipped to the pane. A base line is always included.

Settings

ChartSettings is compared by value:

Field	Default	Meaning
scale	Linear	Linear, Log (log10 mapping, ticks at nice prices, falls back to linear while any visible value, indicator mark or base line value is zero or negative) or Percent (change against the base line, the previous close when the base line is None)
axisSide	Right	Left or Right
rightMargin	3	blank candle slots after the last candle; the larger of it and an indicator extension applies, clamped to half the plot
grid	Horizontal	None, Horizontal, Vertical, Both
crosshair	true	whether a long press shows the crosshair
legend	true	header and pane legends
currentPrice	true	last price line and axis tag, the tag carries the change percent when a base exists
baseLine	None	None, PreviousClose, TodayOpen, Pivot, Custom(value) (finite)
highLowMarkers	true	visible high and low values
priceLimits	false	limit lines at the previous close ± limitPercent
limitPercent	30.0	distance of the limit lines
volumeMa	true	MA lines of Volume and TradingValue
fontScale	1f	multiplier of the text size, applies to sized text styles

The previous session close is the close of the last candle of the previous local day for intraday timeframes (device time zone) and the previous candle close for day and longer.

Multi-pane layout and height rules

• chartHeight (default 300.dp) is the height of the main chart area with its header and time axis
• Every pane adds paneHeight × weight (default 80.dp × 1) plus a 4.dp gap, so the default Volume pane gives a total of 384.dp; dragging a separator moves height between the areas and keeps the total
• With several panes the total can exceed the screen: place the panel in a vertically scrollable container (for example Column(Modifier.verticalScroll(rememberScrollState()).navigationBarsPadding())). Vertical drags on the chart scroll that parent, so the last pane and the time axis stay reachable above the navigation bar
• Each pane has its own Y axis, one-line legend, and crosshair value tag with its own format; the legend strip sits above the plot
• The header wraps its legend lines and keeps the tallest wrap seen until the series, the indicators or the width change, so the chart does not jump while the crosshair moves
• Pane resize: long press within 12dp of a separator, then drag. Minimum 120dp for the main area and 40dp for a pane. Heights live in LineChartState, survive data updates and indicator parameter changes, follow their indicator when another pane is removed or inserted, and are not saved across recreation

Real-time updates and LineChartState

rememberLineChartState(items, maxDataPoints, yAxisTicksCount, scaleFactor, strokeWidth) keeps one LineChartState for the lifetime of the composable. Pass a new list on every update.

• The last sample changed or was replaced in place: viewport unchanged
• Samples appended: the chart follows the right edge while it is at the latest sample, and stays anchored when scrolled back or while the crosshair is on
• The crosshair keeps the anchor while it is on; when it is released the chart jumps back to the latest sample if it was following when the crosshair started
• A series that no longer contains the previous last date (for example a timeframe switch): the viewport resets to the latest sample and the zoom is kept
• maxDataPoints > 0 keeps the latest points only
• selected emits only when the crosshair moves to another sample
• The entry reveal plays once

Market components and linechart-orderbook

Components in linechart (foundation only, themed by ChartColors, with price formatters):

Component	Purpose
DepthChart(bids, asks)	Cumulative depth steps with mid line, spread, axes and a long-press crosshair; an empty book draws an empty box
OrderBookLadder(levels, side, onLevelClick)	One side of the book with quantity bars; the tapped price is passed to the callback
TradeList(trades)	Size, price and date columns, ×n for n > 1
OptionSelector(options, selected, onSelect)	Selectable option chips with the best ask or bid
InstantTradeButtons(bestAsk, bestBid, onBuy, onSell)	Buy and sell now buttons
List<MarketTrade>.toDailyChartData()	Daily ChartData for a price history chart: volume is the summed quantity and value is the summed price times quantity

Models are MarketLevel, MarketTrade, MarketOption and MarketSide. Bid uses the up color and ask the down color. String keys are prefixed linechart_market_ and every library resource uses the linechart_ prefix. Tab rows, the bid sheet and the price chart are composed by the app, the demo shows a full screen.

linechart-orderbook

Pure Kotlin matching engine in package tddy.ko.linechart.orderbook, no Android dependency.

val engine = MatchingEngine(
    policy = MatchingPolicy(tickSize = 1_000, minPrice = 1_000),
    feePolicy = FeePolicy { side, price, qty -> minOf(price * qty * 3 / 100, 300_000) },
)
val result = engine.place("230", Side.Buy, OrderType.Limit, quantity = 1, price = 127_000, owner = "me")
val book = engine.snapshot("230", depth = 20)

Semantics:

• Books are independent per option; better price fills first, FIFO within a price, trades execute at the maker price
• Money is Long (KRW), quantities are Int
• Validation: quantity ≤ 0 is InvalidQuantity; a limit price below minPrice or not a multiple of tickSize is InvalidPrice; an expiry not after now is InvalidExpiry. A rejected order consumes no id
• allowCrossing = false rejects a crossing limit order with Crossing; instant orders are never affected
• A partial fill keeps the resting order priority; empty levels are removed
• Instant fills up to an optional price bound and cancels the rest: no fill gives a null orderId with NoLiquidity, a partial fill cancels the remainder with NoLiquidity
• Self trade prevention applies only when owner is set and equals the resting owner: matching stops, the remainder of the incoming order is canceled with SelfTrade, earlier fills stay
• modify(orderId, price, expiresAt) is cancel and replace with the same id and the remaining quantity: priority is lost and it may match. A rejected modify keeps the original. A modify that would self trade cancels the original and returns a non-null orderId with SelfTrade. An expired order not yet reclaimed returns NotFound from modify while order(id) still returns it
• Expiry is lazy: expiresAt is absolute epoch millis, matching skips expired orders, and expire(now) reclaims them sorted by expiry then id. Call it on a timer
• Fees are computed per fill (buyerFee, sellerFee) by a FeePolicy that must not throw; fees of every fill are computed before the book or the id sequence changes, so a throwing policy leaves the book unchanged
• Deterministic: clock and id generator are injected, order and trade ids share one sequence, no hash order is exposed
• Not thread-safe, the caller serializes access. Cancel is O(k) in the orders at a level
• Trade and BookLevel are data classes and closed value types; Order, OrderResult and BookSnapshot are plain classes with toString. BookLevel.quantity is capped at Int.MAX_VALUE

Upgrading from 1.0.x

The 1.0.0 API and binary signatures are kept (LineChartPanel, LineChart, rememberLineChartState, ChartData(cumulativeProfit, date), LineChartState) through hidden shims and verified by a reflection test; a javap diff against the 1.0 jar reports no missing member. Behavior changes:

• Height: chartHeight is the main area only and every pane adds paneHeight × weight + 4.dp. The default Volume pane makes the total 384.dp instead of 300.dp; reduce chartHeight to keep the old total
• The default look is Candle with MA 5/20/60/120 and a Volume pane; pass chartType = ChartType.Line, overlays = emptyList(), panes = emptyList() for a plain line
• New parameters overlays, panes, settings, paneHeight. The 1.1 preview parameter maPeriods and ChartColors.ma are removed, use MovingAverage(periods, colors); Volume and MovingAverage take their own periods and colors
• Pan, zoom and the crosshair are on and the crosshair hides on release; a tap no longer selects a sample, a long press does
• The price axis is on the right and the time axis is drawn by the library
• The default palette is Korean (red up, blue down) and follows the system dark mode
• A header shows OHLC, change and the legends
• maxDataPoints keeps the latest points (takeLast)
• formatValue uses #,##0.## independent of the default locale
• Fewer than 2 items draw an empty box instead of nothing
• The gray split right of the crosshair is gone
• The entry reveal plays once, not on every state change
• An opaque colors.background is drawn behind the chart; use Color.Transparent to show the parent
• The labels argument of the legacy LineChartState constructor is ignored, the axis shows the item number or the time
• DragSelection.position snaps to the candle center and interpolatedValue equals the value
• Moving averages are excluded from the Y range, so a far-off average no longer flattens the candles
• ChartData gained open, high, low, volume and value; the old constructor and copy stay
• material3 is no longer a transitive dependency

Compatibility

• 1.0.x callers compile and link unchanged; LineChartAbiTest covers every 1.0 signature by reflection
• Built with Gradle 9.9.0, AGP 9.5.1, Kotlin 2.4.21 (API and language level 2.2), compileSdk 37, Compose 1.12.1

License

Apache License 2.0