In computing, DirectInput is a legacy MicrosoftAPI for collecting input from a computer user, via input devices such as the mouse, keyboard, or a gamepad. It also provides a system for action mapping, which allows the user to assign specific actions within a game to the buttons and axes of the input devices. Additionally it handles haptic feedback devices. Microsoft introduced a new input library called XInput specifically for the Xbox 360 controller. DirectInput and XInput provide benefits over normal Win32 input events:
they enable an application to retrieve data from input devices even when the application is in the background
they provide full support for any type of input device, as well as for haptic feedback
through action mapping, applications can retrieve input data without needing to know what kind of device generated that input
While DirectInput forms a part of the DirectX library, it has not been significantly revised since DirectX 8. Microsoft recommends that new applications make use of the Windows message loop for keyboard and mouse input instead of DirectInput, and to use XInput instead of DirectInput for Xbox 360 controllers.
History
DirectX included DirectInput from version 1.0. It initially offered true support only for joysticks, as the mouse and keyboard modules simply provided wrappers to the standard Win32 API. DirectX version 3.0 added support for keyboards and mice; it also improved joystick support. DirectX 5.0 included greatly improved joystick support, including adding haptic feedback, increasing the number of buttons, changing the underlying device-driver model and incorporating a COM-based API. Mouse support also increased the number of buttons seen from four to eight. In DirectX 7.0, DirectInput added a long-promised feature of seeing individual mice much like individual joysticks, but the feature didn't work with the later released Windows XP, even though it works with Windows 98/Me and DirectX 9. DirectX 8.0, the last version with major changes, included action mapping and broader support for different types of devices. While Microsoft initially intended that DirectInput would handle all inputs, it hasn't turned out this way. Microsoft doesn't recommend using DirectInput for keyboards or mice, and has started pushing the newer XInput for Xbox 360 controllers. In Windows Vista, Windows 7 and later Windows versions, the in-built action mapping UI has been removed. DirectInput is not available for Windows Store apps.
XInput
XInput, an API for "next generation" controllers, was introduced in December 2005 alongside the launch of the Xbox 360. This instruction set provided full support for Xbox 360 controllers in Windows XP SP1 and subsequent operating systems, and is described by Microsoft as being easier to program for and requiring less setup than DirectInput. XInput is compatible with DirectX version 9 and later.
An Xbox 360 Controller, with the default Microsoft driver, has the following limitations with DirectInput, compared to XInput:
the left and right triggers will act as a single axis representing the signed difference between the triggers, not as independent analog axes
vibration effects will not operate
querying for headset devices will not operate
None of these limitations exist if using the Xbox 360 Controller with XInput. Vibration effects will not work on the Xbox One Controller. According to MSDN, "the combination of the left and right triggers in DirectInput is by design. Games have always assumed that DirectInput device axes are centered when there is no user interaction with the device. However, the Xbox 360 controller was designed to register minimum value, not center, when the triggers are not being held." MSDN proffered the "solution" of combining the triggers, setting one trigger to a positive direction and the other to a negative direction, so no user interaction is indicative to DirectInput of the "control" being at center. The above, however, ignores the fact that many DirectInput controllers, such as gamepads with dual analog sticks and racing-wheel controller sets, already map triggers and pedals independently. In addition, many DirectInput devices also have vibration effects. At least one driver, XBCD, gives the Xbox 360 controllers the vibration support, dead zones and independent triggers through DirectInput. This suggests that Microsoft's Xbox 360 controller driver intentionally has weaker DirectInput support, rather than due to any differences between DirectInput and XInput APIs. On the other hand, Xbox 360 controller and XInput support only very basic control of vibration motors in contrast with great palette of various effects supported by DirectInput.
DirectInput vs XInput
Microsoft has not made any major changes to DirectInput since DirectX 8, and introduced XInput later in DirectX 9: there remains some confusion about the current status and future of the two APIs. The XInput API also has limits that DirectInput does not:
XInput supports only "next generation" controllers. This limits it basically to controllers for the Xbox 360 that also have Windows drivers. Legacy Windows controllers, joysticks and generalized haptic feedback devices are not supported.
XInput supports a maximum of four controllers at a time. This is an Xbox limit, carried over to Windows. Although few PC games require more than four controllers at once, DirectInput itself has no such limitation.
XInput does not support keyboards, mice, or mouse-type devices. While this mirrors Microsoft's recommendation not to use DirectInput with these devices, programmers can use DirectInput with these devices.
XInput supports maximum of 4 axes, 10 buttons, 2 triggers and 8-direction digital pad per controller, compared to DirectInput's support for 8 axes, 128 buttons, and full-range POV.
Advantage of XInput over DirectInput:
When used with an Xbox 360 Controller, the left and right trigger buttons will act independently, instead of as a single button
XInput is for Xbox 360 controllers, while DirectInput is for any controller. In XInput 1.4 introduced with Windows 8 support of querying for headset devices was reintroduced.
