Imported from ad-repo/nullplayer (skills/tripex-port/SKILL.md). Install upstream with npx skills add ad-repo/nullplayer --skill tripex-port. Copyright stays with the author.

Tripex Port Guide

Tripex is a visualization engine in NullPlayer's modern visualizer window, switchable from the right-click Visualization Engine submenu alongside ProjectM, Geiss, and Met Museum. It is a port of the MIT-licensed upstream at https://github.com/ben-marsh/tripex (vendored verbatim into Sources/CTripexCore/upstream/).

Architecturally simpler than the Geiss port: Tripex already has a clean Renderer abstract base in upstream, so the port substitutes one concrete subclass (RendererOpenGL) for the Direct3D 9 implementation that ships upstream. There is no asm to translate (Geiss had 30+ blocks), no Winamp 2 SDK stub, and no DirectDraw indexed-framebuffer plumbing — the renderer pushes geometry through a small GLSL 150 shader pair.

The port inherits the visualizer window's CVDisplayLink-driven render cadence, fullscreen toggle, and engine-switch lifecycle. It is not available in CLI/headless mode — VisualizationType is not exposed there.

File Layout

Sources/CTripexCore/

Compiled vs excluded

Package.swift excludes the following from the CTripexCore C++ target:

• upstream/main.cpp — Win32 message-loop shell. Beat detection, effect switching, fade timing all already live inside Tripex::Render — nothing to re-home.
• upstream/RendererDirect3d.{cpp,h} — D3D9 backend, replaced by RendererOpenGL.
• upstream/AudioDevice.{cpp,h} — WaveOut output, replaced by NullPlayer's audio pump → HostAudioSource.
• Build-system files (*.vcxproj*, *.sln, packages.config, LICENSE, README.md).

Everything else under upstream/ plus all of upstream_port/ is compiled.

cxxSettings: headerSearchPath("."), headerSearchPath("include"), headerSearchPath("upstream"), headerSearchPath("upstream_port"), define("__APPLE__"), unsafeFlags(["-fno-strict-aliasing", "-fwrapv"]).

Package-level cxxLanguageStandard is C++17 (Tripex uses std::shared_ptr<uint8[]>). C++17 is backwards compatible with CGeissCore and CVisClassicCore.

Exceptions are present in upstream (Error.cpp throws); clang's default -fexceptions covers this — no extra flag needed.

Threading model

• Audio thread (NullPlayer's audio pump tap) → TripexEngine.addPCMMono(_:) → TripexCore_pushPCM → HostAudioSource::Push → ring buffer write under HostAudioSource::mutex_.
• Render thread (CVDisplayLink) → TripexEngine.renderFrame() → TripexCore_renderFrame → Tripex::Render(*audio) → effect calculations + AudioSource::Read (ring buffer read under the same mutex).
• Main thread (right-click menu) → TripexEngine.nextEffect() / selectEffect(at:) / etc. → TripexCore_nextEffect etc.

Two mutexes are at play:

1. TripexCoreHandle::lock serializes every public ABI entry inside TripexCore.cpp. Audio push and render frame are NEVER executed concurrently — pushPCM holds the lock while writing to the ring buffer; renderFrame holds it for the full Tripex frame.
2. HostAudioSource::mutex_ is an inner lock guarding the ring-buffer state. Redundant in practice because the outer ABI lock already serializes producer/consumer, but kept so the class is correct in isolation.

TripexEngine.coreLock (Swift) guards the Swift-side handle pointer + scratch buffer; the C handle itself is thread-safe under its own mutex.

Audio path

PCM is delivered by NullPlayer as mono float in [-1, 1]. TripexEngine.addPCMMono converts to interleaved int16 stereo (left = right = sample × 32767, clamped) and pushes the entire buffer in one shot. Tripex computes its own FFT inside upstream/Fourier.cpp (radix-2 + Hann-style apodization on raw int16 samples) — no Accelerate / vDSP work is done on the Swift side for Tripex (contrast: Geiss requires ~66 lines of Hann + radix-2 + dB-normalize in VisualizationGLView.updateGeissSpectrumFromPCM).

AudioSource::Read (Tripex contract) takes a byte count. Effects typically request <4 KB per frame; the ring buffer holds ~2 seconds, so under any realistic display-link cadence the buffer never underruns. If audio ever pauses for >2 seconds, Read pads with silence and Tripex renders against silence — visually equivalent to "no sound", which is correct.

Rendering

Tripex::Render(audio_source) orchestrates the per-frame work: dispatch transition-state flags (txs), update audio analysis (AudioData), pick / advance / fade the active effect, call effect->Render(params) which in turn calls Renderer::DrawIndexedPrimitive. The renderer subclass converts each VertexTL (screen-space pre-projected) + Face (3 uint16 indices) batch into a single glDrawElements(GL_TRIANGLES, ...) call.

VertexTL layout (32 bytes): Vector3 position, float rhw, ColorRgb diffuse, ColorRgb specular, Point<float> tex_coords[1]. The Swift-side GL context must be a 3.2 core profile (NullPlayer's VisualizationGLView provides this). The shader pair lives inline in RendererOpenGL.cpp as kVertexShaderSrc / kFragmentShaderSrc.

Implemented texture paths

• RendererOpenGL::CreateTextureFromImage decodes embedded JPG/PNG/etc. through the ImageIO/CoreGraphics helper in ImageDecode.cpp.
• OpenGLTexture::SetDirty re-uploads dynamic textures, including P8 palette expansion, so Canvas-based effects can animate. Dynamic P8 uploads reuse a per-texture scratch buffer.
• OpenGLTexture::GetPixelData reads back BGRA pixels with glGetTexImage, which EffectBumpmapping uses while reconfiguring.

Effect timing and performance notes

• Tripex::Render uses per-frame timing (frames = ...), not accumulated skipped-frame timing. Effects with custom CanRenderImpl gates may need review if they stall under this model.
• Flowmap, MotionBlur1, and Phased have already been adjusted for the per-frame timing model.
• Tube and WaterGlobe are the main current performance-sensitive effects. Both avoid the transparent z pre-pass in the OpenGL port; an attempted analytic/radial normal optimization made them look worse and was reverted.
• If Tube/WaterGlobe still need more speed, the next deliberate tradeoff is mesh LOD, especially WaterGlobe's CreateTetrahedronGeosphere(200, 5).

C ABI surface (full)

TripexCoreHandle* TripexCore_create(int width, int height);
void              TripexCore_destroy(TripexCoreHandle*);
void              TripexCore_resize(TripexCoreHandle*, int w, int h);
void              TripexCore_pushPCM(TripexCoreHandle*, const int16_t* samples, size_t count);
int               TripexCore_renderFrame(TripexCoreHandle*);
void              TripexCore_prevEffect(TripexCoreHandle*);
void              TripexCore_nextEffect(TripexCoreHandle*);
void              TripexCore_changeEffect(TripexCoreHandle*);
void              TripexCore_reconfigureEffect(TripexCoreHandle*);
void              TripexCore_toggleHoldingEffect(TripexCoreHandle*);
void              TripexCore_toggleAudioInfo(TripexCoreHandle*);
void              TripexCore_toggleHelp(TripexCoreHandle*);
void              TripexCore_setHold(TripexCoreHandle*, int on);
int               TripexCore_isHolding(TripexCoreHandle*);
void              TripexCore_setIntensityScale(TripexCoreHandle*, float scale);
float             TripexCore_getIntensityScale(TripexCoreHandle*);
int               TripexCore_effectCount(TripexCoreHandle*);
const char*       TripexCore_effectName(TripexCoreHandle*, int index);
int               TripexCore_currentEffectIndex(TripexCoreHandle*);
void              TripexCore_selectEffect(TripexCoreHandle*, int index);
void              TripexCore_setOption(TripexCoreHandle*, const char* key, int value);
int               TripexCore_getOption(TripexCoreHandle*, const char* key, int fallback);
const char*       TripexCore_lastError(TripexCoreHandle*);

_selectEffect maps the user-facing index to enabled_effects[index + 1] to hide Tripex's internal "Blank" fade helper. It jumps directly through PortJumpToEffect, resets fade state, and reconfigures the target effect.

Persistence

UserDefaults keys, persisted via UserDefaults.standard:

• tripex.lastEffectIndex (Int) — restores last selected effect.
• tripex.cycleMode (String) — off, cycle, or random.
• tripex.cycleInterval (Double) — seconds between Swift-driven effect changes.
• tripex.intensityScale (Float) — engine-level audio/intensity multiplier.

The Tripex _setOption / _getOption store is currently unused by any UI surface — reserved for future options that do not deserve dedicated ABI. The tripex.lockedEffectIndex constant is reserved in TripexEngine.DefaultsKey but not currently read or written.

Menu surface

TripexMenuBuilder.addTripexConfigMenuItems(to:target:visualizationView:) produces the per-engine submenu when Tripex is the active engine. Surface:

• Current effect name (disabled label).
• Next / Previous / Random / Randomize Effect Settings.
• Hold Current Effect.
• Auto-Cycle / Auto-Random + Cycle Interval. Clicking the checked auto mode unchecks it and disables cycling; there is no separate "Manual Only" item.
• Intensity submenu (0.25x through 4.0x).
• Show Audio Info / Show Help Overlay (toggle actions).
• Effects submenu listing all enabled effects with a checkmark on currentTripexEffectIndex.

TripexMenuTarget is the @objc protocol the host view conforms to. ModernProjectMView implements it and forwards each action to the corresponding VisualizationGLView.*Tripex* helper.

Tripex does not expose native per-effect sliders. The exposed "levers" are the native engine-level controls that make sense in NullPlayer: hold, cycle mode, cycle interval, intensity, randomize current effect settings, and overlays.

Mode-specific guards (per CLAUDE.md gotcha)

• isTripexActive = currentEngineType == .tripex is computed in ModernProjectMView's menu builder. The addTripexEffectsMenuItems call is gated on it.
• selectTripexEffect, nextTripexEffect, etc. in VisualizationGLView all early-return via withTripex if the active engine is not TripexEngine — defensive against menu actions firing during an engine switch.

Architectural deviations from upstream

1. Renderer backend — D3D9 replaced by OpenGL 3.2 core (NSOpenGLView). RendererDirect3d.{cpp,h} excluded; RendererOpenGL.{cpp,h} substituted.
2. Audio backend — WaveOut device replaced by host audio tap. AudioDevice.{cpp,h} excluded; HostAudioSource.{cpp,h} substituted. NullPlayer's audio engine is the source of truth, and Tripex consumes a synthesized in-memory stream.
3. No window — upstream's WinMain is excluded; the host NSOpenGLView owns the framebuffer / GL context / display-link cadence. Tripex doesn't know whether it's rendering to a real window or an offscreen FBO.
4. Host keyboard routing — upstream binds F1/F2/Left/Right/R/E/H/M/O/T inside WndProc. NullPlayer routes bare key events from the ProjectM host windows to Tripex helpers for previous/next/random and relies on native menus for the rest.
5. Port helpers in Tripex.h — PortGetEffectCount/PortGetEffectName/PortGetCurrentEffectIndex, direct jump, deterministic hold, and intensity scale. Upstream keeps this state private; the C ABI needs it for menus and Swift-driven cycling.
6. One inline edit to Platform.h — #error Unsupported compiler. replaced with #include "win_compat.h" under the _MSC_VER #else branch.

Adding a Tripex configuration menu item

1. Add a getter/setter pair in TripexCore.h if the new option requires a real binding (otherwise use _setOption/_getOption with a key string).
2. Add a Swift accessor on TripexEngine and a forwarding wrapper on VisualizationGLView (mutex-guarded by engineLock).
3. Append the menu item in TripexMenuBuilder.addTripexConfigMenuItems.
4. Add the action selector to TripexMenuTarget and implement it on ModernProjectMView.
5. If the option is user-persistent, write to UserDefaults in the action handler and read it back in the .tripex factory branch of VisualizationGLView.createEngine.

Common modifications

Modifying the render path

• Shader source: top of RendererOpenGL.cpp (kVertexShaderSrc / kFragmentShaderSrc).
• VAO/VBO attribute layout: RendererOpenGL::EnsurePipeline.
• Blend / depth / cull translation: ApplyBlendMode / ApplyDepthMode in RendererOpenGL.cpp.

Adding a new upstream effect

Effects auto-register via the EXPORT_EFFECT(name, type) macro at the bottom of each EffectFoo.cpp. To add one:

1. Drop the .cpp into upstream/ (or upstream_port/ if it's a NullPlayer-specific effect).
2. Reference its CreateEffect_Foo symbol from Tripex::CreateEffects in upstream/Tripex.cpp.
3. No SwiftPM change needed — the file is picked up automatically.

Modifying the audio path

• Ring buffer capacity: HostAudioSource::RING_CAPACITY in HostAudioSource.h.
• Float→int16 conversion / mono→stereo broadcasting: TripexEngine.addPCMMono in Swift.

Gotchas

• NEVER include <chrono> (or any other C++-only header) at file scope in win_compat.h — Swift compiles the CTripexCore clang module in C mode for the importer and the umbrella sweep pulls in win_compat.h via TripexCore.h's transitive includes (the public-headers directory). Anything C++-only must be #ifdef __cplusplus.
• Out-of-class definitions for upstream static const members — MSVC accepts the in-class initializer as a definition; clang/C++17 ODR-uses (vector::push_back, function param by const&) require an out-of-class definition. Add to upstream_port/tripex_compat.cpp.
• Renderer's base destructor is non-virtual upstream — ~RendererOpenGL is intentionally NOT marked override to satisfy clang. Memory under std::shared_ptr<Renderer> still calls the correct destructor through shared_ptr's type-erased deleter, but if any future code holds Renderer* raw and deletes it polymorphically, behavior is undefined.
• Effect.cpp filename case — most upstream includes use lowercase effect.h and error.h; the files on disk are Effect.h / Error.h. macOS APFS is case-insensitive by default, so it works; clang emits -Wnonportable-include-path warnings (suppressible, presently kept visible as a reminder).
• Engine switching corruption risk — RendererOpenGL lazily creates its GL pipeline on first draw. After TripexCore_destroy, GL resources are released through OpenGLTexture::~OpenGLTexture, but the shared VAO/VBO/IBO are leaked (no destructor cleanup) — minor. Add cleanup in RendererOpenGL::~RendererOpenGL if engine-switch leaks become noticeable.

Verification matrix

After modifying any of the touched files, run:

1. swift build — green, including all upstream .cpp files compiling without error.
2. Launch app → right-click visualizer → Visualization Engine → Tripex → confirm the window switches and a frame renders.
3. Use the per-engine submenu items (Next / Previous / Random / Randomize Effect Settings / Hold / Auto-Cycle / Auto-Random / Intensity / Show Audio Info / Show Help / Effects submenu entries) → confirm each takes effect.
4. Switch back to ProjectM → confirm no GL state corruption.
5. Close + relaunch app with Tripex saved as last-engine + non-zero tripex.lastEffectIndex → confirm the same effect restores.
6. Run with a long-playing track (>10 min) → Activity Monitor should show steady-state memory, no growth.

Upstream provenance

• Source: https://github.com/ben-marsh/tripex, MIT license (Copyright (c) 2025 Ben Marsh).
• Vendored from src/Tripex/* (97 files including LICENSE/README).
• LICENSE and README.md retained verbatim under upstream/ but excluded from compilation.
• Upstream edits are intentionally small but no longer limited to the initial Platform.h and PortGet* accessors. Current port patches include timing, menu/control helpers, selected effect fixes, and Tube/WaterGlobe performance fixes. See PORT_STATUS.md before changing behavior.