archie/tk4.2/generic/tkError.c
2024-05-27 16:40:40 +02:00

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/*
* tkError.c --
*
* This file provides a high-performance mechanism for
* selectively dealing with errors that occur in talking
* to the X server. This is useful, for example, when
* communicating with a window that may not exist.
*
* Copyright (c) 1990-1994 The Regents of the University of California.
* Copyright (c) 1994-1995 Sun Microsystems, Inc.
*
* See the file "license.terms" for information on usage and redistribution
* of this file, and for a DISCLAIMER OF ALL WARRANTIES.
*
* SCCS: @(#) tkError.c 1.20 96/02/15 18:53:17
*/
#include "tkPort.h"
#include "tkInt.h"
/*
* The default X error handler gets saved here, so that it can
* be invoked if an error occurs that we can't handle.
*/
static int (*defaultHandler) _ANSI_ARGS_((Display *display,
XErrorEvent *eventPtr)) = NULL;
/*
* Forward references to procedures declared later in this file:
*/
static int ErrorProc _ANSI_ARGS_((Display *display,
XErrorEvent *errEventPtr));
/*
*--------------------------------------------------------------
*
* Tk_CreateErrorHandler --
*
* Arrange for all a given procedure to be invoked whenever
* certain errors occur.
*
* Results:
* The return value is a token identifying the handler;
* it must be passed to Tk_DeleteErrorHandler to delete the
* handler.
*
* Side effects:
* If an X error occurs that matches the error, request,
* and minor arguments, then errorProc will be invoked.
* ErrorProc should have the following structure:
*
* int
* errorProc(clientData, errorEventPtr)
* caddr_t clientData;
* XErrorEvent *errorEventPtr;
* {
* }
*
* The clientData argument will be the same as the clientData
* argument to this procedure, and errorEvent will describe
* the error. If errorProc returns 0, it means that it
* completely "handled" the error: no further processing
* should be done. If errorProc returns 1, it means that it
* didn't know how to deal with the error, so we should look
* for other error handlers, or invoke the default error
* handler if no other handler returns zero. Handlers are
* invoked in order of age: youngest handler first.
*
* Note: errorProc will only be called for errors associated
* with X requests made AFTER this call, but BEFORE the handler
* is deleted by calling Tk_DeleteErrorHandler.
*
*--------------------------------------------------------------
*/
Tk_ErrorHandler
Tk_CreateErrorHandler(display, error, request, minorCode, errorProc, clientData)
Display *display; /* Display for which to handle
* errors. */
int error; /* Consider only errors with this
* error_code (-1 means consider
* all errors). */
int request; /* Consider only errors with this
* major request code (-1 means
* consider all major codes). */
int minorCode; /* Consider only errors with this
* minor request code (-1 means
* consider all minor codes). */
Tk_ErrorProc *errorProc; /* Procedure to invoke when a
* matching error occurs. NULL means
* just ignore matching errors. */
ClientData clientData; /* Arbitrary value to pass to
* errorProc. */
{
register TkErrorHandler *errorPtr;
register TkDisplay *dispPtr;
/*
* Find the display. If Tk doesn't know about this display then
* it's an error: panic.
*/
dispPtr = TkGetDisplay(display);
if (dispPtr == NULL) {
panic("Unknown display passed to Tk_CreateErrorHandler");
}
/*
* Make sure that X calls us whenever errors occur.
*/
if (defaultHandler == NULL) {
defaultHandler = XSetErrorHandler(ErrorProc);
}
/*
* Create the handler record.
*/
errorPtr = (TkErrorHandler *) ckalloc(sizeof(TkErrorHandler));
errorPtr->dispPtr = dispPtr;
errorPtr->firstRequest = NextRequest(display);
errorPtr->lastRequest = (unsigned) -1;
errorPtr->error = error;
errorPtr->request = request;
errorPtr->minorCode = minorCode;
errorPtr->errorProc = errorProc;
errorPtr->clientData = clientData;
errorPtr->nextPtr = dispPtr->errorPtr;
dispPtr->errorPtr = errorPtr;
return (Tk_ErrorHandler) errorPtr;
}
/*
*--------------------------------------------------------------
*
* Tk_DeleteErrorHandler --
*
* Do not use an error handler anymore.
*
* Results:
* None.
*
* Side effects:
* The handler denoted by the "handler" argument will not
* be invoked for any X errors associated with requests
* made after this call. However, if errors arrive later
* for requests made BEFORE this call, then the handler
* will still be invoked. Call XSync if you want to be
* sure that all outstanding errors have been received
* and processed.
*
*--------------------------------------------------------------
*/
void
Tk_DeleteErrorHandler(handler)
Tk_ErrorHandler handler; /* Token for handler to delete;
* was previous return value from
* Tk_CreateErrorHandler. */
{
register TkErrorHandler *errorPtr = (TkErrorHandler *) handler;
register TkDisplay *dispPtr = errorPtr->dispPtr;
errorPtr->lastRequest = NextRequest(dispPtr->display) - 1;
/*
* Every once-in-a-while, cleanup handlers that are no longer
* active. We probably won't be able to free the handler that
* was just deleted (need to wait for any outstanding requests to
* be processed by server), but there may be previously-deleted
* handlers that are now ready for garbage collection. To reduce
* the cost of the cleanup, let a few dead handlers pile up, then
* clean them all at once. This adds a bit of overhead to errors
* that might occur while the dead handlers are hanging around,
* but reduces the overhead of scanning the list to clean up
* (particularly if there are many handlers that stay around
* forever).
*/
dispPtr->deleteCount += 1;
if (dispPtr->deleteCount >= 10) {
register TkErrorHandler *prevPtr;
TkErrorHandler *nextPtr;
int lastSerial;
dispPtr->deleteCount = 0;
lastSerial = LastKnownRequestProcessed(dispPtr->display);
errorPtr = dispPtr->errorPtr;
for (errorPtr = dispPtr->errorPtr, prevPtr = NULL;
errorPtr != NULL; errorPtr = nextPtr) {
nextPtr = errorPtr->nextPtr;
if ((errorPtr->lastRequest != -1)
&& (errorPtr->lastRequest <= lastSerial)) {
if (prevPtr == NULL) {
dispPtr->errorPtr = nextPtr;
} else {
prevPtr->nextPtr = nextPtr;
}
ckfree((char *) errorPtr);
continue;
}
prevPtr = errorPtr;
}
}
}
/*
*--------------------------------------------------------------
*
* ErrorProc --
*
* This procedure is invoked by the X system when error
* events arrive.
*
* Results:
* If it returns, the return value is zero. However,
* it is possible that one of the error handlers may
* just exit.
*
* Side effects:
* This procedure does two things. First, it uses the
* serial # in the error event to eliminate handlers whose
* expiration serials are now in the past. Second, it
* invokes any handlers that want to deal with the error.
*
*--------------------------------------------------------------
*/
static int
ErrorProc(display, errEventPtr)
Display *display; /* Display for which error
* occurred. */
register XErrorEvent *errEventPtr; /* Information about error. */
{
register TkDisplay *dispPtr;
register TkErrorHandler *errorPtr;
/*
* See if we know anything about the display. If not, then
* invoke the default error handler.
*/
dispPtr = TkGetDisplay(display);
if (dispPtr == NULL) {
goto couldntHandle;
}
/*
* Otherwise invoke any relevant handlers for the error, in order.
*/
for (errorPtr = dispPtr->errorPtr; errorPtr != NULL;
errorPtr = errorPtr->nextPtr) {
if ((errorPtr->firstRequest > errEventPtr->serial)
|| ((errorPtr->error != -1)
&& (errorPtr->error != errEventPtr->error_code))
|| ((errorPtr->request != -1)
&& (errorPtr->request != errEventPtr->request_code))
|| ((errorPtr->minorCode != -1)
&& (errorPtr->minorCode != errEventPtr->minor_code))
|| ((errorPtr->lastRequest != -1)
&& (errorPtr->lastRequest < errEventPtr->serial))) {
continue;
}
if (errorPtr->errorProc == NULL) {
return 0;
} else {
if ((*errorPtr->errorProc)(errorPtr->clientData,
errEventPtr) == 0) {
return 0;
}
}
}
/*
* See if the error is a BadWindow error. If so, and it refers
* to a window that still exists in our window table, then ignore
* the error. Errors like this can occur if a window owned by us
* is deleted by someone externally, like a window manager. We'll
* ignore the errors at least long enough to clean up internally and
* remove the entry from the window table.
*/
if ((errEventPtr->error_code == BadWindow) && (Tk_IdToWindow(display,
(Window) errEventPtr->resourceid) != NULL)) {
return 0;
}
/*
* We couldn't handle the error. Use the default handler.
*/
couldntHandle:
return (*defaultHandler)(display, errEventPtr);
}