To avoid flooding the clients with events in which they have no
interest, they must explicitly tell the server which events they are
interested in. This is done by providing the event_mask
attribute when creating windows with Window.create_window or in
calls to Window.change_attributes. The value of this attribute
is a mask of all types of events the client is interested in on that
particular window. Whenever the server generates an event for a window
which matches the clients event mask on that window, the event will be
sent to the client.
The following table lists all event masks and the corresponding event
types and classes. All event masks and types are integer constants
defined in the module Xlib.X. Classes have the same name as the
event type, and are defined in Xlib.protocol.event.
| Mask | Type and Class | Generated when |
| ButtonMotionMask Button1MotionMask Button2MotionMask Button3MotionMask Button4MotionMask Button5MotionMask |
MotionNotify | Pointer moved with any or a certain button down |
| ButtonPressMask | ButtonPress | Pointer button pressed |
| ButtonReleaseMask | ButtonRelease | Pointer button released |
| ColormapChangeMask | ColormapNotify | Colormap changed or installed |
| EnterWindowMask | EnterNotify | Pointer enters window |
| LeaveWindowMask | LeaveNotify | Pointer leaves window |
| ExposureMask | Expose NoExpose |
Window needs to be redrawn |
| FocusChangeMask | FocusIn FocusOut |
Focus changes |
| KeymapStateMask | KeymapNotify | After EnterNotify and FocusIn |
| KeyPressMask | KeyPress | Key is pressed |
| KeyReleaseMask | ReleasePress | Key is released |
| PointerMotionMask | MotionNotify | Pointer is moved |
| PropertyChangeMask | PropertyNotify | Window properties change |
| StructureNotifyMask | CirculateNotify ConfigureNotify DestroyNotify GravityNotify MapNotify ReparentNotify UnmapNotify | Window structure changes |
| SubstructureNotifyMask | CirculateNotify ConfigureNotify CreateNotify DestroyNotify GravityNotify MapNotify ReparentNotify UnmapNotify | Child window structure changes |
| ResizeRedirectMask | ResizeRequest | Controlling window size change |
| SubstructureRedirectMask | CirculateRequest ConfigureRequest MapRequest | Controlling changes to child windows |
| VisibilityChangeMask | VisibilityNotify | Window is obscured or visible |
There are also some event types which are always sent to the clients, regardless of any event masks:
| Type and Class | Cut'n'pasting between windows |
| ClientMessage | Other client sends message |
| MappingMotify | Keyboard mapping changes |
| SelectionClear |
SelectionNotify Cut'n'pasting between windows |
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