KMPCharts/CHANGELOG.md

Changelog

All notable changes to chart-realtime documented here.

Format follows Keep a Changelog. Project adheres to Semantic Versioning from 1.0.0 onward.

Pre-1.0.0 releases share the 0.5.0-SNAPSHOT Maven coordinate per group:dev.dtrentin, artifact:chart-realtime. Stable coordinates and Maven Central publishing land in 1.0.0.

Unreleased

Changed

• KGP 2.3 / AGP 9 deprecation warnings cleanup (in progress)

0.5.0 — 2026-05-22 — Architecture + Interaction

Added

• Interaction layer (T7) — pinch zoom, drag pan, tap crosshair via ChartInteractionState
  • rememberChartInteractionState(). ViewportMode sealed (Following / Frozen / History(anchorMs)). Swipe-to-right-edge resumes Following. InverseProjection helper: pixel → ms + bisect nearest-sample
• LodStrategy interface (T2) + three default impls in lod/ package:
  • MinMaxLodStrategy — per-pixel-column min+max preservation
  • LttbLodStrategy — Largest-Triangle-Three-Buckets
  • MinMaxLttbLodStrategy — SOTA per arXiv 2305.00332, 1.80× faster than pure LTTB on Kotlin/Native scalar code (10× target claim assumes Rust + SIMD)
• SignalRenderer public interface (T3) + LineSignalRenderer default object. Custom renderer impl-able in ~30 LOC. Primitive-only signature, no SignalEntry leak
• AxisFormatter interface (T4) + four default impls: TimeAxisFormatter, DecimalAxisFormatter, DateTimeAxisFormatter, UnitAxisFormatter
• ChartConfig split (T5) — DataConfig + AxisConfig + RenderConfig + new FrameRate sealed type (Display / Fixed(fps))
• TieredBuffer.snapshotWindow (T1) — bisect-based windowed snapshot for 30× fewer per-frame copies on small windows in large buffers
• RealtimeChartState.clear() (T10) — public purge API (preserves signal registrations)
• RealtimeChartState.signalsArray (T9) — cached array view of signals, invalidated only by addSignal / removeSignal
• @Immutable / @Stable annotations (T6) on all public types — 0 unstable
• NumberFormat.formatFixed overflow guard (D4) — routes to scientific @ |v|≥1e19

Changed (BREAKING)

• Removed LodMode enum — replaced by LodStrategy interface
• Removed LodDecimator internal class — replaced by LodStrategy impls
• Removed ChartConfig.targetFps field — replaced by RenderConfig.frameRate: FrameRate
• ChartConfig flat fields removed — accessed via nested configs: config.data.xWindowSeconds, config.render.theme, config.axis.xLabelMode, etc. Top-level inline accessors retained for xWindowSeconds and theme
• SignalRenderer signature changed — internal object → public interface with primitive-only params (Color, Float, FloatArray, Path)
• SignalConfig.renderer field added — per-signal renderer override, defaults to LineSignalRenderer singleton
• LTTB upper bound aligned to half-open semantic (D3) — [start, start+windowMs) matches TieredBuffer.snapshot. Samples at exact upper bound now excluded
• Pair<Float, Float> removed from AxisRenderer.resolveYRange — replaced by FloatArray out param

Performance

• LineSignalRenderer caches Stroke instances per strokeWidth (T8)
• AxisRenderer caches TextStyle instances (16-entry cap)
• Render path: 0 Pair/Map/Iterator allocations per frame at steady state

Toolchain

• Kotlin 2.1.0 → 2.3.21
• Compose Multiplatform 1.8.0 → 1.11.0
• Android Gradle Plugin 8.7.3 → 9.2.0
• Gradle 8.11.1 → 9.5.1
• coroutines 1.9.0 → 1.11.0; kotlin-test → 2.3.21
• Dropped kotlinx-datetime — replaced by stdlib kotlin.time.Clock (Kotlin 2.3 stable)
• Dropped iosX64 target — Compose Multiplatform 1.11.0 no longer ships ios_x64 variants (Intel Mac iOS simulators deprecated by Apple since Xcode 15+)

Tests

• 107 → 207 (+100). Coverage: lod/ (24), interaction/ (29), model/ChartConfigTest (8), render/AxisFormatterTest (10), RealtimeChartStateTest (+9), NumberFormatTest (+6), TieredBufferTest (+10), CircularBufferTest (+10), AxisRendererTest (3), LineSignalRendererTest (2)

API surface

• chart-realtime.api: 161 → 428 LOC
• chart-realtime.klib.api: 211 → 501 LOC

0.4.0 — 2026-05-21 — Portfolio Hardening

15 tasks shipped via 3-reviewer audit (android-reviewer + mobile-performance-reviewer + mobile-architect). Library moved from "prototype" to "senior-engineer-built KMP library".

Added

• LICENSE MIT
• explicitApi() Strict + Binary Compatibility Validator (BCV) 0.16.3 + klib enabled
• ABI baseline locked (chart-realtime.api 161 LOC, chart-realtime.klib.api 211 LOC)
• hasData boolean flag (replaces POSITIVE_INFINITY / Float.MAX_VALUE sentinels)
• Snapshot.withMutableSnapshot + SnapshotApplyConflictException retry helper
• M4 binning for Tier1/Tier2 (firstTs/V, minTs/V, maxTs/V, lastTs/V) with chronological dedup
• NaN/Inf/backward-timestamp guards on push; per-signal lastPushedTs tracking
• NumberFormat extracted from AxisRenderer (38 tests)
• 25 buffer/LoD tests (tier roll, window crossing, clear, LTTB branches)

Changed

• CircularBuffer.writeIndex Int → Long (fixes 124d overflow @ 200Hz)
• kotlinx-datetime 0.6.2 replaces expect/actual currentTimeMs (Platform.kt deleted)
• dataVersion → mutableLongStateOf (Compose-observable, idle = 0 recompositions)
• Single buffer.snapshot() per signal per frame via per-signal scratch arrays
• TIER1_CAPACITY 12k → 24k, TIER2_CAPACITY 5.4k → 10.8k (×2 → ×4 for M4 binning)
• Memory per signal: ~760 KB → ~1.14 MB

Removed

• RenderLoop.kt, rememberFrameTick (deleted)
• maxBufferSeconds, xLabelDecimals, SignalConfig.label (dead config)
• All !! and @Suppress("UNUSED_EXPRESSION") from commonMain

Internal lockdown

• CircularBuffer, TieredBuffer, LodDecimator, dataVersion, rememberFrameTick, capacity constants

Tests

• 33 → 107 (+74)

0.3.0 — 2026-05-21 — iOS Build Pipeline + Dirty Flag Render

Added

• iOS targets compile + link green: iosX64, iosArm64, iosSimulatorArm64
• applyDefaultHierarchyTemplate() auto-wires iosMain / iosTest
• XCFramework ChartRealtime (debug + release): ios-arm64 + ios-arm64_x86_64-simulator
• Dirty-flag render: dataVersion counter, skip Canvas draw when no new data
• targetFps = 30 default in ChartConfig (null = max display refresh rate)
• iOS-side Platform.ios.kt: NSDate() + timeIntervalSinceReferenceDate + 1970 epoch offset (978_307_200s)
• KDoc on RealtimeChart, RealtimeChartState, ChartConfig, LodMode, AxisLabelMode
• README sections: LoD, AxisLabels, Material3

Fixed

• Multiplatform replacements for JVM-only String.format: formatFixed / formatScientific / pow10 helpers in AxisRenderer
• kotlin.concurrent.Volatile + kotlin.jvm.JvmName imports (OptionalExpectation)
• X axis: show negative values instead of clamping to "0s"

Tests

• 17 → 33 (RealtimeChartStateTest: dataVersion + signal lifecycle)

0.2.0 — 2026-05-21 — Polish

Added

• TieredBuffer: 3-tier ring buffer (5min full-rate, 10min @ 10Hz, 45min @ 1Hz), ~5MB footprint for 1h of data
• LodMode.LTTB (Largest-Triangle-Three-Buckets, O(n) decimation)
• AxisLabelMode (INSIDE / BESIDE / HIDDEN) with chartLeft / chartBottom insets
• T0-relative X-axis timestamps with mm:ss / hh:mm:ss formatting (negative supported)
• Material3 dynamic theming (light/dark, wallpaper-based, API 31+)
• Camera cutout / edge-to-edge support
• Sensor domain layer (Clean Architecture)
• Koin 4.0.0 DI wiring
• Sensor rate cap: 200Hz (5_000μs)

Changed

• Package rename: eu.henesis → dev.dtrentin
• TieredBuffer binning: MEAN → MIN_MAX (composable across tier boundaries, no synthetic values, no C7 spike artifacts)
• LodDecimator: pre-allocated scratch arrays (zero GC at render time)

Removed

• LodMode.MEAN (introduced synthetic values absent in raw signal)

0.1.0 — 2026-05-20 — MVP

Initial implementation. Six phases shipped:

1. Module scaffold (KMP + Compose Multiplatform + Android library)
2. CircularBuffer + LodDecimator
3. RealtimeChartState API
4. RealtimeChart composable + Canvas-based SignalRenderer + AxisRenderer
5. Demo app (:app)
6. Polish + initial docs