type Button int32

const (
    ButtonNone      Button = +0
    ButtonLeft      Button = +1
    ButtonMiddle    Button = +2
    ButtonRight     Button = +3
    ButtonWheelUp   Button = -1
    ButtonWheelDown Button = -2
)

type Direction uint8

const (
    DirNone    Direction = 0
    DirPress   Direction = 1
    DirRelease Direction = 2
)

type Event struct {
    // X and Y are the mouse location, in pixels.
    X, Y float32

    // Button is the mouse button being pressed or released. Its value may be
    // zero, for a mouse move or drag without any button change.
    Button Button

    // Modifiers is a bitmask representing a set of modifier keys:
    // key.ModShift, key.ModAlt, etc.
    Modifiers key.Modifiers

    // Direction is the direction of the mouse event: DirPress, DirRelease,
    // or DirNone (for mouse moves or drags).
    Direction Direction
}