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lightning-sunbird  0.9+nobinonly
jGNE.cpp
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00001 /* ***** BEGIN LICENSE BLOCK *****
00002  * Version: MPL 1.1/GPL 2.0/LGPL 2.1
00003  *
00004  * The contents of this file are subject to the Mozilla Public License Version
00005  * 1.1 (the "License"); you may not use this file except in compliance with
00006  * the License. You may obtain a copy of the License at
00007  * http://www.mozilla.org/MPL/
00008  *
00009  * Software distributed under the License is distributed on an "AS IS" basis,
00010  * WITHOUT WARRANTY OF ANY KIND, either express or implied. See the License
00011  * for the specific language governing rights and limitations under the
00012  * License.
00013  *
00014  * The Original Code is the MRJ Carbon OJI Plugin.
00015  *
00016  * The Initial Developer of the Original Code is
00017  * Netscape Communications Corp.
00018  * Portions created by the Initial Developer are Copyright (C) 2001
00019  * the Initial Developer. All Rights Reserved.
00020  *
00021  * Contributor(s):
00022  *   Patrick C. Beard <beard@netscape.com>
00023  *
00024  * Alternatively, the contents of this file may be used under the terms of
00025  * either of the GNU General Public License Version 2 or later (the "GPL"),
00026  * or the GNU Lesser General Public License Version 2.1 or later (the "LGPL"),
00027  * in which case the provisions of the GPL or the LGPL are applicable instead
00028  * of those above. If you wish to allow use of your version of this file only
00029  * under the terms of either the GPL or the LGPL, and not to allow others to
00030  * use your version of this file under the terms of the MPL, indicate your
00031  * decision by deleting the provisions above and replace them with the notice
00032  * and other provisions required by the GPL or the LGPL. If you do not delete
00033  * the provisions above, a recipient may use your version of this file under
00034  * the terms of any one of the MPL, the GPL or the LGPL.
00035  *
00036  * ***** END LICENSE BLOCK ***** */
00037 
00038 /*
00039        jGNE.cpp
00040        
00041        Provides a generalized jGNE filtering service.
00042        
00043        by Patrick C. Beard.
00044  */
00045 
00046 #include "jGNE.h"
00047 
00048 #include <MixedMode.h>
00049 #include <Memory.h>
00050 #include <LowMem.h>
00051 #include <TextUtils.h>
00052 
00056 #pragma options align=mac68k
00057 
00058 struct Jump {
00059        unsigned short              jmp;
00060        UniversalProcPtr     addr;
00061 };
00062  
00063 #pragma options align=reset
00064 
00065 static void GNEFilter(EventRecord *event, Boolean* result);
00066 
00067 static RoutineDescriptor theGNEFilterDescriptor = BUILD_ROUTINE_DESCRIPTOR(uppGetNextEventFilterProcInfo, GNEFilter);
00068 static Jump* theGNEFilterJump;
00069 static GetNextEventFilterUPP theOldGNEFilterUPP = NULL;
00070 static EventFilterProcPtr  theEventFilter = NULL;
00071 
00072 static Str63 theAppName;
00073 
00074 OSStatus InstallEventFilter(EventFilterProcPtr filter)
00075 {
00076        if (theEventFilter == NULL) {
00077               theEventFilter = filter;
00078 
00079               // record the current application's name.
00080               StringPtr currentAppName = LMGetCurApName();
00081               ::BlockMoveData(currentAppName, theAppName, 1 + currentAppName[0]);
00082 
00083               // allocate a jump vector in the System heap, so it will be retained after termination.
00084               if (theGNEFilterJump == NULL) {
00085                      theGNEFilterJump = (Jump*) NewPtrSys(sizeof(Jump));
00086                      if (theGNEFilterJump == NULL)
00087                             return MemError();
00088                      
00089                      theGNEFilterJump->jmp = 0x4EF9;
00090                      theGNEFilterJump->addr = &theGNEFilterDescriptor;
00091                      
00092                      // get previous event filter routine.
00093                      theOldGNEFilterUPP = LMGetGNEFilter();
00094                      LMSetGNEFilter(GetNextEventFilterUPP(theGNEFilterJump));
00095               } else {
00096                      // our previously allocated Jump is still installed, use it.
00097                      theOldGNEFilterUPP = theGNEFilterJump->addr;
00098                      theGNEFilterJump->addr = &theGNEFilterDescriptor;
00099               }
00100               
00101               return noErr;
00102        }
00103        return paramErr;
00104 }
00105 
00106 OSStatus RemoveEventFilter()
00107 {
00108        if (theEventFilter != NULL) {
00109               // It's only truly safe to remove our filter, if nobody else installed one after us.
00110               if (LMGetGNEFilter() == GetNextEventFilterUPP(theGNEFilterJump)) {
00111                      // can safely restore the old filter.
00112                      LMSetGNEFilter(theOldGNEFilterUPP);
00113                      DisposePtr(Ptr(theGNEFilterJump));
00114                      theGNEFilterJump = NULL;
00115               } else {
00116                      // modify the jump instruction to point to the previous filter.
00117                      theGNEFilterJump->addr = theOldGNEFilterUPP;
00118               }
00119               theOldGNEFilterUPP = NULL;
00120               theEventFilter = NULL;
00121               return noErr;
00122        }
00123        return paramErr;
00124 }
00125 
00126 static void GNEFilter(EventRecord *event, Boolean* result)
00127 {
00128        // call next filter in chain first.
00129        if (theOldGNEFilterUPP != NULL)
00130               CallGetNextEventFilterProc(theOldGNEFilterUPP, event, result);
00131 
00132        // now, let the filter proc have a crack at the event.
00133        if (*result) {
00134               // only call the filter if called in the current application's context.
00135               /* if (::EqualString(theAppName, LMGetCurApName(), true, true)) */
00136               {
00137                      // prevent recursive calls to the filter.
00138                      static Boolean inFilter = false;
00139                      if (! inFilter) {
00140                             inFilter = true;
00141                             Boolean filteredEvent = theEventFilter(event);
00142                             if (filteredEvent) {
00143                                    // consume the event by making it a nullEvent.
00144                                    event->what = nullEvent;
00145                                    *result = false;
00146                             }
00147                             inFilter = false;
00148                      }
00149               }
00150        }
00151 }