Buffered Joystick Data

To retrieve buffered data from the joystick, first set the buffer size (see Device Properties) and declare an array of DIDEVICEOBJECTDATA types. This array can have up to the same number of elements as the buffer size. You do not have to retrieve the entire contents of the buffer with a single call. You can have just one element in the array and retrieve events one at a time until the buffer is empty.

After acquiring the device, you can examine and flush the buffer at any time with the DirectInputDevice8.GetDeviceData method. (See Buffered and Immediate Data.)

Each element in the DIDEVICEOBJECTDATA array represents a change in state for a single object on the joystick. For instance, if the user presses button 0 and moves the stick diagonally, the array passed to GetDeviceData (if it has at least three elements) will have three elements filled in—an element for button 0 being pressed, an element for the change in the x-axis, and an element for the change in the y-axis—and the return value of the method will be 3.

You can determine which object an element in the array refers to by checking the lOfs member of the DIDEVICEOBJECTDATA type against the constants of the CONST_DIJOYSTICKOFS enumeration. Each of these values is equivalent to the offset of the data for the object in a DIJOYSTATE type. For example, DIJOFS_BUTTON0 is equivalent to the offset of buttons(0) in the DIJOYSTATE type.

If the data format was set with DIFORMAT_JOYSTICK2, you can use the offset constants for all the device objects that exist in DIJOYSTATE, but you must supply your own offsets for device objects represented in the extra members of DIJOYSTATE2. The internal organization of this type is the same as that of the equivalent C++ structure in the Dinput.h header file.

The data for the change of state of the device object is located in the lData member of the DIDEVICEOBJECTDATA type. For axes, the coordinate value is returned in this member. For button objects, only the low byte of lData is significant. The high bit of this byte is set if the button is pressed, and it is clear if the button is released.

For the other members, see Time Stamps and Sequence Numbers.