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Annotation of 43BSD/contrib/X/doc/Xlib/ch13a.t, revision 1.1.1.1

1.1       root        1: .NH
                      2: Error Handling
                      3: .XS
                      4: Error Handling
                      5: .XE
                      6: .PP
                      7: .IN "Error Handlers"
                      8: There are two default error handlers in the library, one to handle
                      9: typically fatal conditions (for example, the connection to a display
                     10: server
                     11: dying due to machine crash), and one to handle error events from X.
                     12: These error handlers can be changed to user supplied routines if you
                     13: prefer your own error handling, and can be changed as often as you like.
                     14: If either of these routines are passed a NULL pointer, it will
                     15: reinvoke the default handler.
                     16: The default action of the  supplied routine is to exit.
                     17: .PP
                     18: .FD
                     19: .IN "Definitions" "XIOErrorHandler"
                     20: .IN "XIOErrorHandler"
                     21: XIOErrorHandler( handler )
                     22:        int handler(Display *);
                     23: .FN
                     24: .PP
                     25: The program's
                     26: supplied error handler will be called by Xlib if any sort of system call error
                     27: occurs, e.g. the connection to the server was lost.
                     28: This is assumed to
                     29: be a fatal condition, i.e., the called routine should not return.
                     30: If the IO error handler
                     31: does return, the client process will exit.
                     32: .PP
                     33: .FD
                     34: .IN "Definitions" "XErrorHandler"
                     35: .IN "XErrorHandler"
                     36: XErrorHandler( handler )
                     37:        int handler(Display *, XErrorEvent *)
                     38: .FN
                     39: The program's
                     40: supplied error hander will be called by Xlib whenever an \fIXError\fP event is
                     41: received.
                     42: This is not assumed to be a fatal condition, i.e., it is
                     43: acceptable for this procedure to return.
                     44: However, the error handler should NOT
                     45: perform any operations (directly or indirectly) on the Display.
                     46: The
                     47: fields of the \fIXErrorEvent\fP passed to \fIXError\fP should be interpreted as follows:
                     48: .sp
                     49: .DS
                     50: .TA .5i 2.5i
                     51: .ta .5i 2.5i
                     52: typedef struct _XErrorEvent {
                     53:        long pad;
                     54:        long serial;    /* serial number of failed request */
                     55:        char error_code;        /* error code of failed request */
                     56:        char request_code;      /* request code of failed request */
                     57:        char func;      /* function field of failed request */
                     58:        char pad_b7;
                     59:        Window window;  /* Window of failed request */
                     60:        long pad_l3;
                     61:        long pad_l4;
                     62: } XErrorEvent;
                     63: .DE
                     64: .IN "Data Structures" "XErrorEvent"
                     65: .IN "Serial Number"
                     66: .sp
                     67: The serial number is the number of requests sent over the network connection
                     68: since it was opened, starting from one; it is the number that was the
                     69: value of \fIdpy->request\fP immediately after the failing call was made.  The
                     70: request code is a protocol representation of the name of the procedure
                     71: .IN "File" "<X/X.h>"
                     72: that failed; these are defined in \fI<X/X.h>\fP.  The error code is one of
                     73: the following, also defined in \fI<X/X.h>\fP:
                     74: .IN "Error Numbers"
                     75: .LP
                     76: .TS
                     77: center,box;
                     78: lcl.
                     79: BadRequest     1       bad request code
                     80: BadValue       2       int parameter out of range
                     81: BadWindow      3       parameter not a Window
                     82: BadPixmap      4       parameter not a Pixmap
                     83: BadBitmap      5       parameter not a Bitmap
                     84: BadCursor      6       parameter not a Cursor
                     85: BadFont        7       parameter not a Font
                     86: BadMatch       8       parameter mismatch
                     87: BadTile        9       Pixmap shape invalid for tiling
                     88: BadGrab        10      mouse/button already grabbed
                     89: BadAccess      11      access control violation
                     90: BadAlloc       12      insufficient resources
                     91: BadColor       13      no such color
                     92: .TE
                     93: It is recommended that \fIXError\fP use the following procedure for obtaining
                     94: textual descriptions of errors:
                     95: .FD
                     96: .IN "Definitions" "XErrDescrip"
                     97: .IN "XErrDescrip"
                     98: char *XErrDescrip (code)
                     99:        int code;
                    100: .FN
                    101: Returns a null-terminated string describing the specified error code.
                    102: The string is static in Xlib and should not be modified or freed.

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