FastLED FX: Internal Helpers (detail/)

This folder contains utilities used by the FX engine. Most apps won’t include these directly; they’re pulled in by higher‑level classes.

Components

• draw_context.h: Defines fl::_DrawContext (commonly referred to via Fx::DrawContext), which carries per‑frame data into effects: now (ms), CRGB* leds, frame_time, and a speed hint.
• fx_layer.h: Wraps an Fx and a Frame surface. Manages start/pause/draw and exposes the surface for compositing.
• fx_compositor.h: Cross‑fades between two FxLayers over time using Transition. Produces a final buffer by blending surfaces each frame; automatically completes when progress reaches 100%.
• transition.h: Tracks a time‑based 0–255 progress value between a start time and duration. Used by the compositor to animate transitions.

When you’ll encounter these

• If you use an FX engine/controller that switches effects with fades.
• If you build your own multi‑effect player, you may interact with FxLayer and FxCompositor directly.

These pieces are small and dependency‑light, but they’re part of the internal plumbing for higher‑level modules.

Examples

• Switching between effects with transitions (see examples/FxEngine/FxEngine.ino):
  cppCopy

  #include <FastLED.h>
  #include "fx/2d/noisepalette.h"
  #include "fx/fx_engine.h"
  using namespace fl;
  #define W 22
  #define H 22
  #define NUM_LEDS (W*H)
  CRGB leds[NUM_LEDS];
  XYMap xyMap(W, H, /* serpentine? */ true);
  NoisePalette a(xyMap), b(xyMap);
  FxEngine engine(NUM_LEDS);
  void setup(){ FastLED.addLeds<WS2811,2,GRB>(leds, NUM_LEDS).setScreenMap(xyMap); engine.addFx(a); engine.addFx(b); }
  void loop(){ EVERY_N_SECONDS(1){ engine.nextFx(500); } engine.draw(millis(), leds); FastLED.show(); }