XSetErrorHandler(3)

1XSetErrorHandler(3)             XLIB FUNCTIONS             XSetErrorHandler(3)
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3
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NAME

6       XSetErrorHandler, XGetErrorText, XDisplayName, XSetIOErrorHandler, XSe‐
7       tIOErrorExitHandler, XGetErrorDatabaseText - default error handlers
8

SYNTAX

10       int (*XSetErrorHandler(int (*handler)(Display *, XErrorEvent *)))();
11
12       int XGetErrorText(Display *display, int code, char *buffer_return,  int
13              length);
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15       char *XDisplayName(_Xconst char *string);
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17       int (*XSetIOErrorHandler(int (*handler)(Display *)))();
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19       void (*XSetIOErrorExitHandler(Display *display, void (*handler)(Display
20              *, void *), void *user_data))();
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22       int XGetErrorDatabaseText(Display *display, _Xconst char *name, _Xconst
23              char  *message,  _Xconst  char *default_string, char *buffer_re‐
24              turn, int length);
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ARGUMENTS

27       buffer_return
28                 Returns the error description.
29
30       code      Specifies the error code for which you want to obtain  a  de‐
31                 scription.
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33       default_string
34                 Specifies  the  default error message if none is found in the
35                 database.
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37       display   Specifies the connection to the X server.
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39       handler   Specifies the program's supplied error handler.
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41       length    Specifies the size of the buffer.
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43       message   Specifies the type of the error message.
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45       name      Specifies the name of the application.
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47       string    Specifies the character string.
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DESCRIPTION

50       Xlib generally calls the program's supplied error handler  whenever  an
51       error  is  received.  It is not called on BadName errors from OpenFont,
52       LookupColor, or AllocNamedColor protocol requests or on BadFont  errors
53       from  a  QueryFont  protocol  request.   These errors generally are re‐
54       flected back to the program through the procedural interface.   Because
55       this  condition  is  not assumed to be fatal, it is acceptable for your
56       error handler to return; the returned value is ignored.   However,  the
57       error handler should not call any functions (directly or indirectly) on
58       the display that will generate protocol requests or that will look  for
59       input events.  The previous error handler is returned.
60
61       The  XGetErrorText  function copies a null-terminated string describing
62       the specified error code into the specified buffer.  The returned  text
63       is  in  the encoding of the current locale.  It is recommended that you
64       use this function to obtain an error description because extensions  to
65       Xlib may define their own error codes and error strings.
66
67       The  XDisplayName  function  returns  the  name  of  the  display  that
68       XOpenDisplay would attempt to use.  If  a  NULL  string  is  specified,
69       XDisplayName  looks  in the environment for the display and returns the
70       display name that XOpenDisplay would attempt to  use.   This  makes  it
71       easier  to  report  to the user precisely which display the program at‐
72       tempted to open when the initial connection attempt failed.
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74       The XSetIOErrorHandler sets the fatal I/O error  handler.   Xlib  calls
75       the  program's  supplied error handler if any sort of system call error
76       occurs (for example, the connection to the server was lost).   This  is
77       assumed to be a fatal condition, and the called routine should normally
78       not return.  If the I/O error handler does return, the  client  process
79       exits  by default, this behavior may be altered with the XSetIOErrorEx‐
80       itHandler function.
81
82       Note that the previous error handler is returned.
83
84       The XGetErrorDatabaseText function returns  a  null-terminated  message
85       (or  the  default  message) from the error message database.  Xlib uses
86       this function internally to look up its error messages.   The  text  in
87       the  default_string  argument  is  assumed to be in the encoding of the
88       current locale, and the text stored in the buffer_return argument is in
89       the encoding of the current locale.
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91       The  name  argument  should  generally be the name of your application.
92       The message argument should indicate which type of  error  message  you
93       want.   If  the name and message are not in the Host Portable Character
94       Encoding, the result is implementation-dependent.  Xlib uses three pre‐
95       defined  “application  names” to report errors.  In these names, upper‐
96       case and lowercase matter.
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98       XProtoError
99                 The protocol error number is used as a string for the message
100                 argument.
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102       XlibMessage
103                 These are the message strings that are used internally by the
104                 library.
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106       XRequest  For a core protocol request, the major request protocol  num‐
107                 ber  is  used for the message argument.  For an extension re‐
108                 quest, the extension name (as given  by  InitExtension)  fol‐
109                 lowed  by  a period (.) and the minor request protocol number
110                 is used for the message argument.  If no string is  found  in
111                 the  error  database,  the  default_string is returned to the
112                 buffer argument.
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NAME

SYNTAX

ARGUMENTS

DESCRIPTION

SEE ALSO