From 72c0cbcb38732b698d33d52459fed67af56ee2ec Mon Sep 17 00:00:00 2001
From: skal <pascal.massimino@gmail.com>
Date: Sat, 31 Jan 2026 15:36:45 +0100
Subject: feat: Implement Sequence and Effect system for demo choreography

Refactors the rendering pipeline into a modular Sequence/Effect system. 'MainSequence' manages the final frame rendering and a list of 'Sequence' layers. 'Sequence' manages a timeline of 'Effect' objects (start/end/priority). Concrete effects (Heptagon, Particles) are moved to 'demo_effects.cc'. Updates main loop to pass beat and aspect ratio.
---
 src/gpu/effect.h | 117 +++++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 117 insertions(+)
 create mode 100644 src/gpu/effect.h

(limited to 'src/gpu/effect.h')

diff --git a/src/gpu/effect.h b/src/gpu/effect.h
new file mode 100644
index 0000000..50b2d72
--- /dev/null
+++ b/src/gpu/effect.h
@@ -0,0 +1,117 @@
+// This file is part of the 64k demo project.
+// It defines the Effect interface and Sequence management system.
+// Used for choreographing visual effects.
+
+#pragma once
+
+#include <vector>
+#include <memory>
+#include <algorithm>
+
+#if defined(DEMO_CROSS_COMPILE_WIN32)
+#include <webgpu/webgpu.h>
+#else
+#include <webgpu.h>
+#endif
+
+class MainSequence;
+
+// Abstract base class for all visual effects
+class Effect {
+public:
+  virtual ~Effect() = default;
+
+  // One-time setup (load assets, create buffers).
+  // Idempotent: safe to call multiple times if effect is shared.
+  virtual void init(MainSequence *demo) { (void)demo; }
+
+  // Called when the effect starts playing in a sequence segment.
+  virtual void start() {}
+
+  // Dispatch compute shaders.
+  virtual void compute(WGPUCommandEncoder encoder, float time, float beat,
+                       float intensity, float aspect_ratio) {
+    (void)encoder;
+    (void)time;
+    (void)beat;
+    (void)intensity;
+    (void)aspect_ratio;
+  }
+
+  // Record render commands.
+  virtual void render(WGPURenderPassEncoder pass, float time, float beat,
+                      float intensity, float aspect_ratio) = 0;
+
+  // Called when the effect finishes in a sequence segment.
+  virtual void end() {}
+  
+  bool is_initialized = false;
+};
+
+struct SequenceItem {
+  std::shared_ptr<Effect> effect;
+  float start_time; // Relative to Sequence start
+  float end_time;   // Relative to Sequence start
+  int priority;     // Render order within sequence (higher = later/top)
+  bool active;
+};
+
+class Sequence {
+public:
+  int priority = 0; // Render order of this sequence (higher = later/top)
+
+  void init(MainSequence *demo);
+  
+  // Add an effect to the sequence.
+  // start_time, end_time: Relative to sequence start.
+  // priority: Drawing order within this sequence.
+  void add_effect(std::shared_ptr<Effect> effect, float start_time,
+                  float end_time, int priority = 0);
+
+  // Updates active state of effects based on sequence-local time.
+  // seq_time: Time relative to sequence start.
+  void update_active_list(float seq_time);
+
+  // Calls compute() on all active effects (sorted by priority).
+  void dispatch_compute(WGPUCommandEncoder encoder, float seq_time, float beat,
+                        float intensity, float aspect_ratio);
+
+  // Calls render() on all active effects (sorted by priority).
+  void dispatch_render(WGPURenderPassEncoder pass, float seq_time, float beat,
+                       float intensity, float aspect_ratio);
+
+  void reset();
+
+private:
+  std::vector<SequenceItem> items_;
+  bool is_sorted_ = false;
+  void sort_items();
+};
+
+class MainSequence {
+public:
+  WGPUDevice device;
+  WGPUQueue queue;
+  WGPUTextureFormat format;
+
+  void init(WGPUDevice device, WGPUQueue queue, WGPUTextureFormat format);
+  
+  // Add a sequence to the demo.
+  // start_time: Global time when this sequence starts.
+  // priority: Layering order (higher = on top).
+  void add_sequence(std::shared_ptr<Sequence> seq, float start_time, int priority = 0);
+
+  // Renders the full frame: updates sequences, runs compute, runs render pass.
+  void render_frame(float global_time, float beat, float peak,
+                    float aspect_ratio, WGPUSurface surface);
+
+  void shutdown();
+
+private:
+  struct ActiveSequence {
+    std::shared_ptr<Sequence> seq;
+    float start_time;
+    int priority;
+  };
+  std::vector<ActiveSequence> sequences_;
+};
-- 
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