Editing Scroll wheel (section)

==Functionality==

===Scrolling===
Rotating the wheel sends vertical scroll commands in many graphical desktop systems. In many systems, the panel or control under the cursor is scrolled; in [[Microsoft Windows]], however, it's far more common for the scroll events to be sent to whichever control has the focus. This behaviour can be modified through many programs.

Most wheels have tactile detents (notches), each corresponding to a scrolling step. There are typically 24 detents per revolution, but some wheels have only 18.
When a electromechanical [[rotary encoder]] is used, the detents tend to be a property of it. When an optoelectric encoder is used instead, the detents are created by a separate spring.

In Microsoft Windows, each step is a fixed amount of three lines of text.
Faster rotation of the wheel in some systems, including in Apple's [[macOS]], increases the scroll distance per step to provide accelerated scrolling.
Scrolling acceleration is also provided as a feature in the Microsoft IntelliPoint driver software supplied with the IntelliMouse.

===Smooth scrolling===
In [[Microsoft Windows|Windows ''Vista'']], Microsoft introduced a protocol on top of [[USB|USB HID]] for smoother scrolling with higher resolution than per detent.

When a mouse powers up it should not do smooth scrolling by default but when Windows boots it would tell the mouse to increase its resolution.<ref>Microsoft - [http://www.microsoft.com/whdc/device/input/wheel.mspxEnhanced Wheel Support in Windows]. Dated 2010-11-10. Retrieved 2016-04-06.</ref>

However, some of [[Microsoft]]'s own mice suffer from a bug that it does not reset its internal resolution when the host reboots. This has the effect that when users dual-boots from Windows into an operating system that does not support the protocol, 
scrolling is much too fast. Workarounds includes power-cycling the mouse (re-plugging) and to run a specific utility which sends the mouse the appropriate message.<ref>Ubuntu Answers - [https://answers.launchpad.net/ubuntu/+question/9200 Change scroll wheel speed].Retrieved 2016-10-30.</ref>

===Mouse button three===
Most scroll wheels work as mouse button three when pressed straight down.
The button is often heavier than other buttons.

PC mice before scroll wheels traditionally followed two competing standards: Logitech's and Microsoft's. Logitech favoured three-button mice, and Microsoft favoured two. First with [[Microsoft]]'s first scroll wheel-equipped [[Microsoft IntelliMouse|IntelliMouse]], did they make the transition of three-button mice, but putting it under the wheel.

This non-obvious functionality, together with traditionally limited adoption by Windows and software applications, has lead to a general lack of awareness of this additional button. The number of websites that fail to accept middle-click to open links in a new tab suggests how many web designers alone remain oblivious to this facility.