Double-Click Test Tool - Detailed Working Principle

1. What Information Does a Mouse Send to the Computer?

A mouse only sends three types of information to the computer:

• Button State: Whether a button is pressed or released.
• Displacement Change: The amount of movement on the X and Y axes.
• Scroll Wheel Direction: Whether the wheel is scrolled up or down.

That's correct—you read it right. A mouse does not send a double-click signal to the computer. It only sends time pulses generated by button presses and releases. To be precise, the mouse itself doesn't know what a double-click is. So, how does the computer know when a double-click happens? Where does the computer get the double-click signal? Don't worry; the following section, What is a Double-Click?, explains this.

2. What is a Double-Click?

A double-click occurs when any mouse button is pressed twice within a time threshold, typically 500ms (this threshold is adjustable in different systems/settings; you can see its specific configuration in the Windows/macOS control panel). Such a signal is recognized by the operating system as a double-click. That's right—the double-click signal is defined by the operating system itself. As long as the time pulse signal matches the definition, the OS unhesitatingly recognizes it as a double-click, as shown in the diagram below.

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3. What is a Faulty Double-Click?

A faulty double-click is when the user clicks only once, but due to mouse hardware issues, the system receives multiple click signals, typically with an interval less than 80ms. Human clicking speed simply cannot be this fast, but this time pulse satisfies the operating system's definition of a double-click.

Faulty double-clicks typically manifest as:

• Clicking once opens a file and immediately closes it (selects and deselects).
• Dragging is suddenly interrupted.
• Clicking once in text selects two words.

4. How Do Faulty Double-Clicks Occur?

The root cause of faulty double-clicks lies in abnormal opening and closing of contacts inside the microswitch. Common causes include:

• Microswitch Aging: Metal spring fatigue after long-term use, leading to poor rebound.
• Contact Oxidation: Sulfides in the air cause surface oxidation, increasing contact resistance.
• Dust or Debris: Enters the microswitch, causing unstable contact.
• Mechanical Wear: Surface wear on contacts leads to poor contact.

These physical changes cause the circuit to open and close multiple times briefly during a single press, leading the system to mistakenly interpret it as multiple clicks.

5. How This Tool Detects Faulty Double-Clicks

This tool uses high-precision timing and event listeners, combined with intelligent algorithms, to accurately identify abnormal click signals that are not human-generated.

Detection Principle:

• Event Listening: Real-time capture of mouse mousedown and mouseup events.
• Timestamp Recording: Records precise timestamps (millisecond accuracy) for each event.
• Interval Analysis: Calculates the time interval between two consecutive mousedown events.

Judgment Logic:

If the interval between two mousedown events is less than 80ms, it is judged as a faulty double-click. This is because the normal human double-click interval is typically greater than 100ms; consecutive clicks shorter than 80ms are extremely likely caused by hardware bounce.

The tool also counts the number of faulty double-clicks.

6. What Can Mice Do to Reduce Faulty Double-Clicks?

Some high-end mouse brands and models provide debouncing features, allowing users to adjust debouncing parameters via driver software to reduce the occurrence of faulty double-clicks. Below is a state diagram of a mouse's operation after incorporating debouncing functionality.

Below are some examples of mouse brands and models that support debouncing adjustment: