Chapter 4. Errors

In general, when a request terminates with an error, the request has no side effects (that is, there is no partial execution). The only requests for which this is not true are ChangeWindowAttributes, ChangeGC, PolyText8, PolyText16, FreeColors, StoreColors and ChangeKeyboardControl.

The following error codes result from various requests as follows:

Error	Description
Access	An attempt is made to grab a key/button combination already grabbed by another client. An attempt is made to free a colormap entry not allocated by the client or to free an entry in a colormap that was created with all entries writable. An attempt is made to store into a read-only or an unallocated colormap entry. An attempt is made to modify the access control list from other than the local host (or otherwise authorized client). An attempt is made to select an event type that only one client can select at a time when another client has already selected it.
Alloc	The server failed to allocate the requested resource. Note that the explicit listing of Alloc errors in request only covers allocation errors at a very coarse level and is not intended to cover all cases of a server running out of allocation space in the middle of service. The semantics when a server runs out of allocation space are left unspecified, but a server may generate an Alloc error on any request for this reason, and clients should be prepared to receive such errors and handle or discard them.
Atom	A value for an ATOM argument does not name a defined ATOM.
Colormap	A value for a COLORMAP argument does not name a defined COLORMAP.
Cursor	A value for a CURSOR argument does not name a defined CURSOR.
Drawable	A value for a DRAWABLE argument does not name a defined WINDOW or PIXMAP.
Font	A value for a FONT argument does not name a defined FONT. A value for a FONTABLE argument does not name a defined FONT or a defined GCONTEXT.
GContext	A value for a GCONTEXT argument does not name a defined GCONTEXT.
IDChoice	The value chosen for a resource identifier either is not included in the range assigned to the client or is already in use.
Implementation	The server does not implement some aspect of the request. A server that generates this error for a core request is deficient. As such, this error is not listed for any of the requests, but clients should be prepared to receive such errors and handle or discard them.
Length	The length of a request is shorter or longer than that required to minimally contain the arguments. The length of a request exceeds the maximum length accepted by the server.
Match	An InputOnly window is used as a DRAWABLE. In a graphics request, the GCONTEXT argument does not have the same root and depth as the destination DRAWABLE argument. Some argument (or pair of arguments) has the correct type and range, but it fails to match in some other way required by the request.
Name	A font or color of the specified name does not exist.
Pixmap	A value for a PIXMAP argument does not name a defined PIXMAP.
Request	The major or minor opcode does not specify a valid request.
Value	Some numeric value falls outside the range of values accepted by the request. Unless a specific range is specified for an argument, the full range defined by the argument's type is accepted. Any argument defined as a set of alternatives typically can generate this error (due to the encoding).
Window	A value for a WINDOW argument does not name a defined WINDOW.

Note

The Atom, Colormap, Cursor, Drawable, Font, GContext, Pixmap and Window errors are also used when the argument type is extended by union with a set of fixed alternatives, for example, <WINDOW or PointerRoot or None>.