Touch Screen Test: Multi-Touch, Dead Zones & Pressure

The integrity of a touchscreen digitizer is the single most critical factor in the usability of modern mobile devices. Whether validating a refurbished smartphone, testing a DIY screen replacement, or debugging complex gesture recognizers, precise visual feedback is required. This utility bypasses standard browser scrolling to provide raw access to the hardware's input layer.

Hardware defects often manifest as dead zones (areas unresponsive to input) or ghost touches (signals registered without physical contact). Accurately diagnosing these requires a coordinate system capable of tracking high-frequency polling rates. This tool leverages the Pointer Events API to unify input data from capacitive fingers, resistive styluses, and pressure-sensitive instruments.

Technical accuracy depends on the Device Pixel Ratio (DPR). A standard screen might operate at 1x, while Retina-class displays operate at 2x or 3x density. This application automatically scales the rendering context to match physical hardware pixels, ensuring that drawing artifacts are a result of the digitizer, not the rendering engine.

To calculate the physical density of the display, which affects touch target accuracy, we utilize the relationship between resolution and diagonal size:

Where w is width in pixels, h is height in pixels, and d is the diagonal screen size in inches. The system also tracks pressure sensitivity P normalized to a standard range:

This ensures consistent line weights across devices with and without force sensors.