sdl-waveform

A real-time ECG waveform viewer written in C++17 using SDL2. Simulates a scrolling cardiac waveform (PQRST complex) at 72 BPM with hardware-accelerated, double-buffered rendering.

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Features

• Simulates a physiologically-shaped PQRST cardiac cycle at 72 BPM
• Producer/consumer architecture — waveform data is generated on a background thread and rendered on the main thread
• Double-buffered rendering via SDL2 render targets for tear-free output
• Thread-safe sample buffer with mutex-guarded access
• Resizable window — back-buffer is rebuilt automatically on resize
• Targets ~60 FPS with a 16 ms render loop

Requirements

• macOS (currently built for x86_64)
• Clang with C++17 support
• SDL2 — install via Homebrew:

brew install sdl2

Build

make

Run

make run

Or directly:

./waveform

Controls

Key / Action	Behavior
Esc	Quit
Close window	Quit
Resize window	Rescales display

Project Structure

sdl-waveform/
├── main.cpp      # All source — producer thread, renderer, SDL setup
├── Makefile      # Build rules (clang++, sdl2-config)
└── waveform      # Compiled binary (generated)

Architecture

The application uses two threads:

• Producer thread — recalculates 2000 samples of a PQRST waveform 60 times per second, advancing phase to create the scrolling animation. Writes into a mutex-protected WaveformData buffer.
• Main thread — polls SDL events, then calls onPaint() which locks the buffer, maps samples to screen coordinates, and renders green line segments onto an off-screen texture before blitting to the screen.