Button Display Latency Test App

A Flutter application designed to measure and compare input detection latency and screen render timing across different button implementation methods.

🎯 Purpose

This app helps researchers and developers measure the complete input→display pipeline latency by:

• Comparing Button Implementations: Test different Flutter input detection methods
• High-Precision Timing: Microsecond-accurate measurements using Stopwatch
• Frame-Accurate Rendering: Track exact frame timing using Flutter's scheduleFrameCallback
• External Device Sync: Precise sync pulses for aligning with external measurement tools
• Visual Feedback: Real-time indicators for button presses and sync signals

📱 Features

Button Types Tested

Because different button implementations can have varying latency characteristics, this app includes multiple button types for comparison:

• GestureDetectorTapButton - Uses GestureDetector.onTap
• GestureDetectorTapDownButton - Uses GestureDetector.onTapDown
• GestureDetectorPanDownButton - Uses GestureDetector.onPanDown
• RawGestureDetectorTapButton - Uses RawGestureDetector.onTap
• ListenerPointerDownButton - Uses Listener.onPointerDown

Measurement Capabilities

• Touch Detection: Timestamp when input is first detected
• Frame Timing: Start/end timestamps for frame rendering
• Display Feedback: When visual changes begin/end
• Sync Pulses: Reference signals for external device alignment

Visual Indicators

• White Square (Right): Appears when button is pressed
• White Square (Left): Flashes with sync pulses

🚀 Getting Started

Prerequisites

• Flutter SDK (latest stable)
• iOS/Android device or simulator
• Optional: Force Sensitive Resistor (FSR) and photodiodes for external measurements

Installation

1. Clone the repository

git clone https://github.com/NexusDynamic/button_display_latency
cd button_display_latency

2. Install dependencies

flutter pub get

3. Run the app

flutter run --release

🔬 Usage

Basic Testing

1. Select Button Type: Use dropdown to choose implementation
2. Clear Logs: Start fresh measurement session
3. Test: Tap the main button repeatedly
4. Export: Get CSV data for analysis (via share dialogue)

Advanced Sync Testing with External Devices

For the best results, you should have a Force Sensitive Resistor (FSR) and photodiode connected to your measurement device:

• Position FSR over the main test button
• Position photodiode over the left-side sync square
• Position a second photodiode over the right-side button press indicator
• Connect both to your measurement device (oscilloscope, data logger, etc.) -> Bela / Beaglebone Black code to come soon

Controls

• Clear Logs: Reset all timing data
• Sync Pulse: Generate single sync event (and display)
• Start Sync: Begin continuous sync pulse generation (100ms intervals)
• Stop Sync: End sync pulse generation
• Export Logs: Print CSV data to console

📊 Data Analysis

CSV Output Format

EventType,TimestampMicros,ButtonType,FrameNumber
touchDetected,1234567,GestureDetectorTapButton,
displayStart,1234580,,15
frameStart,1234590,,15
frameEnd,1234610,,15
displayEnd,1284567,,
syncPulse,1300000,,

📄 License

This project is licensed under the MIT License - see the LICENSE file for details.

Considerations

• Android Timing Variance: Sync pulse timing may vary on some Android devices due to system scheduling
• Refresh Rate Limitations: High refresh rate requests may not be honored on all devices
• Precision Limits: Some older devices may have limited timing precision capabilities
• Background Processing: System background tasks may affect timing measurements