xpfe/components/winhooks/nsWindowsHooksUtil.cpp
author Neil Deakin <neil@mozilla.com>
Wed, 27 Aug 2008 08:07:27 -0400
changeset 18445 ab3c77a02ed062dab8e71b0284d9590f60672def
parent 1 9b2a99adc05e53cd4010de512f50118594756650
permissions -rw-r--r--
Bug 356295. Implement HTML5 drag-drop. r=smaug,neil,sr=roc

/* -*- Mode: C++; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
/* ***** BEGIN LICENSE BLOCK *****
 * Version: MPL 1.1/GPL 2.0/LGPL 2.1
 *
 * The contents of this file are subject to the Mozilla Public License Version
 * 1.1 (the "License"); you may not use this file except in compliance with
 * the License. You may obtain a copy of the License at
 * http://www.mozilla.org/MPL/
 *
 * Software distributed under the License is distributed on an "AS IS" basis,
 * WITHOUT WARRANTY OF ANY KIND, either express or implied. See the License
 * for the specific language governing rights and limitations under the
 * License.
 *
 * The Original Code is mozilla.org code.
 *
 * The Initial Developer of the Original Code is
 * Netscape Communications Corporation.
 * Portions created by the Initial Developer are Copyright (C) 1998
 * the Initial Developer. All Rights Reserved.
 *
 * Contributor(s):
 *   Bill Law     <law@netscape.com>
 *   Dean Tessman <dean_tessman@hotmail.com>
 *
 * Alternatively, the contents of this file may be used under the terms of
 * either of the GNU General Public License Version 2 or later (the "GPL"),
 * or the GNU Lesser General Public License Version 2.1 or later (the "LGPL"),
 * in which case the provisions of the GPL or the LGPL are applicable instead
 * of those above. If you wish to allow use of your version of this file only
 * under the terms of either the GPL or the LGPL, and not to allow others to
 * use your version of this file under the terms of the MPL, indicate your
 * decision by deleting the provisions above and replace them with the notice
 * and other provisions required by the GPL or the LGPL. If you do not delete
 * the provisions above, a recipient may use your version of this file under
 * the terms of any one of the MPL, the GPL or the LGPL.
 *
 * ***** END LICENSE BLOCK ***** */
#include <windows.h>
#include <stdlib.h>
#include <string.h>

#include "nsString.h"
#include "nsIStringBundle.h"
#include "nsDirectoryService.h"
#include "nsAppDirectoryServiceDefs.h"
#include "nsNativeCharsetUtils.h"
#include "nsWindowsHooksUtil.h"

#ifdef MOZ_XUL_APP
#include "nsNativeAppSupportWin.h"
#else
#include "nsINativeAppSupportWin.h"
#include "nsICmdLineHandler.h"
#endif

#define MOZ_HWND_BROADCAST_MSG_TIMEOUT 5000
#define MOZ_CLIENT_BROWSER_KEY "Software\\Clients\\StartMenuInternet"

// Generate the "full" name of this registry entry.
nsCString RegistryEntry::fullName() const {
    nsCString result;
    if ( baseKey == HKEY_CURRENT_USER ) {
        result = "HKEY_CURRENT_USER\\";
    } else if ( baseKey == HKEY_LOCAL_MACHINE ) {
        result = "HKEY_LOCAL_MACHINE\\";
    } else {
        result = "\\";
    }
    result += keyName;
    if ( !valueName.IsEmpty() ) {
        result += "[";
        result += valueName;
        result += "]";
    }
    return result;
}

// Tests whether registry entry already has desired setting.
PRBool RegistryEntry::isAlreadySet() const {
    PRBool result = FALSE;

    nsCAutoString current( currentSetting() );

    result = ( current == setting );

    return result;
}

// Gives registry entry the desired setting.
nsresult RegistryEntry::set() {
#ifdef DEBUG_law
if ( isNull && setting.IsEmpty() ) printf( "Deleting %s\n", fullName().get() );
else printf( "Setting %s=%s\n", fullName().get(), setting.get() );
#endif
    nsresult result = NS_ERROR_FAILURE;

    HKEY   key;
    LONG   rc = ::RegOpenKey( baseKey, keyName.get(), &key );

    // See if key doesn't exist yet...
    if ( rc == ERROR_FILE_NOT_FOUND ) {
        rc = ::RegCreateKey( baseKey, keyName.get(), &key );
    }
    if ( rc == ERROR_SUCCESS ) {
        if ( isNull && setting.IsEmpty() ) {
            // This means we need to actually remove the value, not merely set it to an
            // empty string.
            rc = ::RegDeleteValue( key, valueNameArg() );
            if ( rc == ERROR_SUCCESS ) {
                result = NS_OK;
            }
        } else {
            NS_ConvertUTF8toUTF16 utf16Setting(setting);
            // Get current value to see if it is set properly already.
            PRUnichar buffer[4096] = { 0 };
            DWORD len = sizeof buffer;
            NS_ConvertASCIItoUTF16 wValueName(valueNameArg());
            rc = ::RegQueryValueExW( key, wValueName.get(), NULL,
                 NULL, (LPBYTE)buffer, &len );
            if ( rc != ERROR_SUCCESS || !utf16Setting.Equals(buffer) ) {
                rc = ::RegSetValueExW( key, wValueName.get(), 0, REG_SZ,
                     (LPBYTE) (utf16Setting.get()),
                     utf16Setting.Length() * 2);
                if ( rc == ERROR_SUCCESS ) {
                   result = NS_OK;
                }
            } else {
                // Already has desired setting.
                result = NS_OK;
            }
        }
        ::RegCloseKey( key );
    } else {
#ifdef DEBUG_law
NS_ASSERTION( rc == ERROR_SUCCESS, fullName().get() );
#endif
    }
    return result;
}

// Get current setting, set new one, then save the previous.
nsresult SavedRegistryEntry::set() {
    nsresult rv = NS_OK;
    PRBool   currentlyUndefined = PR_TRUE;
    nsCAutoString prev( currentSetting( &currentlyUndefined ) );
    // See if value is changing.
    // We need an extra check for the case where we have an empty entry
    // and we need to remove it entirely.
    if ( setting != prev || ( !currentlyUndefined && isNull ) ) {
        // Set new.
        rv = RegistryEntry::set();
        if ( NS_SUCCEEDED( rv ) ) {
            // Save old.
            RegistryEntry tmp( HKEY_LOCAL_MACHINE, "Software\\Mozilla\\Desktop", fullName().get(), prev.get() );
            tmp.set();
        }
    }
    return rv;
}

// setWindowsXP
//
//  We need to:
//    a. Make sure this application is registered as a "Start Menu
//       internet app" under HKLM\Software\Clients\StartMenuInternet.
//    b. Make this app the default "Start Menu internet app" for this
//       user.
static void setWindowsXP() {
    // We test for the presence of this subkey as a WindowsXP test.
    // We do it this way so that vagueries of future Windows versions
    // are handled as best we can.
    HKEY key;
    nsCAutoString baseKey( NS_LITERAL_CSTRING( "Software\\Clients\\StartMenuInternet" ) );
    LONG rc = ::RegOpenKey( HKEY_LOCAL_MACHINE, baseKey.get(), &key );
    if ( rc == ERROR_SUCCESS ) {
        // OK, this is WindowsXP (or equivalent).  Add this application to the
        // set registered as "Start Menu internet apps."  These entries go
        // under the subkey MOZILLA.EXE (or whatever the name of this executable is),
        // that subkey name is generated by the utility function shortAppName.
        ::RegCloseKey(key);
        // The next 3 go under this subkey.
        nsCAutoString subkey( baseKey + NS_LITERAL_CSTRING( "\\" ) + shortAppName() );
        // Pretty name.  This goes into the LocalizedString value.  It is the
        // name of the executable (preceded by '@'), followed by ",-nnn" where
        // nnn is the resource identifier of the string in the .exe.  That value
        // comes from nsINativeAppSupportWin.h.
        char buffer[ _MAX_PATH + 8 ]; // Path, plus '@', comma, minus, and digits (5)
        _snprintf( buffer, sizeof buffer, "@%s,-%d", thisApplication().get(), IDS_STARTMENU_APPNAME );
        RegistryEntry tmp_entry1( HKEY_LOCAL_MACHINE, 
                       subkey.get(),
                       "LocalizedString", 
                       buffer );
        tmp_entry1.set();
        // Default icon (from .exe resource).
        RegistryEntry tmp_entry2( HKEY_LOCAL_MACHINE, 
                       nsCAutoString( subkey + NS_LITERAL_CSTRING( "\\DefaultIcon" ) ).get(),
                       "", 
                       nsCAutoString( thisApplication() + NS_LITERAL_CSTRING( ",0" ) ).get() );
        tmp_entry2.set();
        // Command to open.
        RegistryEntry tmp_entry3( HKEY_LOCAL_MACHINE,
                       nsCAutoString( subkey + NS_LITERAL_CSTRING( "\\shell\\open\\command" ) ).get(),
                       "", 
                       thisApplication().get() );
        tmp_entry3.set();
        // "Properties" verb.  The default value is the text that will appear in the menu.
        // The default value under the command subkey is the name of this application, with
        // arguments to cause the Preferences window to appear.
        nsCOMPtr<nsIStringBundleService> bundleService( do_GetService( "@mozilla.org/intl/stringbundle;1" ) );
        nsCOMPtr<nsIStringBundle> bundle;
        nsXPIDLString label;
        if ( bundleService &&
             NS_SUCCEEDED( bundleService->CreateBundle( "chrome://global-platform/locale/nsWindowsHooks.properties",
                                                   getter_AddRefs( bundle ) ) ) &&
             NS_SUCCEEDED( bundle->GetStringFromName( NS_LITERAL_STRING( "prefsLabel" ).get(), getter_Copies( label ) ) ) ) {
            // Set the label that will appear in the start menu context menu.
            RegistryEntry tmp_entry4( HKEY_LOCAL_MACHINE,
                           nsCAutoString( subkey + NS_LITERAL_CSTRING( "\\shell\\properties" ) ).get(),
                           "", 
                           NS_ConvertUTF16toUTF8( label ).get() );
            tmp_entry4.set();
        }
        RegistryEntry tmp_entry5( HKEY_LOCAL_MACHINE,
                       nsCAutoString( subkey + NS_LITERAL_CSTRING( "\\shell\\properties\\command" ) ).get(),
                       "", nsCAutoString( thisApplication() + 
                                           NS_LITERAL_CSTRING(" -chrome \"chrome://communicator/content/pref/pref.xul\"") ).get()
                      );
        tmp_entry5.set();

        // Now we need to select our application as the default start menu internet application.
        // This is accomplished by first trying to store our subkey name in 
        // HKLM\Software\Clients\StartMenuInternet's default value.  See
        // http://support.microsoft.com/directory/article.asp?ID=KB;EN-US;Q297878 for detail.
        SavedRegistryEntry hklmAppEntry( HKEY_LOCAL_MACHINE, baseKey.get(), "", shortAppName().get() );
        hklmAppEntry.set();
        // That may or may not have worked (depending on whether we have sufficient access).
        if ( hklmAppEntry.currentSetting() == hklmAppEntry.setting ) {
            // We've set the hklm entry, so we can delete the one under hkcu.
            SavedRegistryEntry tmp_entry6( HKEY_CURRENT_USER, baseKey.get(), "", 0 );
            tmp_entry6.set();
        } else {
            // All we can do is set the default start menu internet app for this user.
            SavedRegistryEntry tmp_entry7( HKEY_CURRENT_USER, baseKey.get(), "", shortAppName().get() );
        }
        // Notify the system of the changes.
        ::SendMessageTimeout( HWND_BROADCAST,
                              WM_SETTINGCHANGE,
                              0,
                              (LPARAM)MOZ_CLIENT_BROWSER_KEY,
                              SMTO_NORMAL|SMTO_ABORTIFHUNG,
                              MOZ_HWND_BROADCAST_MSG_TIMEOUT,
                              NULL);
    }
}

// Set this entry and its corresponding DDE entry.  The DDE entry
// must be turned off to stop Windows from trying to use DDE.
nsresult ProtocolRegistryEntry::set() {
    // If the protocol is http, then we have to do special stuff.
    // We must take care of this first because setting the "protocol entry"
    // for http will cause WindowsXP to do stuff automatically for us,
    // thereby making it impossible for us to propertly reset.
    if ( protocol.EqualsLiteral( "http" ) ) {
        setWindowsXP();
    }

    // Set this entry.
    nsresult rv = SavedRegistryEntry::set();

    // Save and set corresponding DDE entry(ies).
    DDERegistryEntry( protocol.get() ).set();
    // Set icon.
    ProtocolIconRegistryEntry( protocol.get() ).set();

    return rv;
}

// Not being a "saved" entry, we can't restore, so just delete it.
nsresult RegistryEntry::reset() {
    HKEY key;
    LONG rc = ::RegOpenKey( baseKey, keyName.get(), &key );
    if ( rc == ERROR_SUCCESS ) {
        rc = ::RegDeleteValue( key, valueNameArg() );
        ::RegCloseKey(key);
#ifdef DEBUG_law
if ( rc == ERROR_SUCCESS ) printf( "Deleting key=%s\n", (const char*)fullName().get() );
#endif
    }
    return NS_OK;
}

// Resets registry entry to the saved value (if there is one).  We first
// ensure that we still "own" that entry (by comparing its value to what
// we would set it to).
nsresult SavedRegistryEntry::reset() {
    nsresult result = NS_OK;

    // Get current setting for this key/value.
    nsCAutoString current( currentSetting() );

    // Test if we "own" it.
    if ( current == setting ) {
        // Unset it, then.  First get saved value it had previously.
        PRBool noSavedValue = PR_TRUE;
        RegistryEntry saved = RegistryEntry( HKEY_LOCAL_MACHINE, mozillaKeyName, fullName().get(), "" );
        // There are 3 cases:
        //    - no saved entry
        //    - empty saved entry
        //    - a non-empty saved entry
        // We delete the current entry in the first case, and restore
        // the saved entry (empty or otherwise) in the other two.
        setting = saved.currentSetting( &noSavedValue );
        if ( !setting.IsEmpty() || !noSavedValue ) {
            // Set to previous value.
            isNull = PR_FALSE; // Since we're resetting and the saved value may be empty, we
                               // need to make sure set() doesn't mistakenly delete this entry.
            result = RegistryEntry::set();
            // Remove saved entry.
            saved.reset();
        } else {
            // No saved value, just delete this entry.
            result = RegistryEntry::reset();
        }
    }

    return result;
}

// resetWindowsXP
//
// This function undoes "setWindowsXP," more or less.  It only needs to restore the selected
// default Start Menu internet application.  The registration of this application as one of
// the start menu internet apps can remain.  There is no check for the presence of anything
// because the SaveRegistryEntry::reset calls will have no effect if there is no value at that
// location (or, if that value has been changed by another application).
static void resetWindowsXP() {
    NS_NAMED_LITERAL_CSTRING( baseKey, "Software\\Clients\\StartMenuInternet" );
    // First, try to restore the HKLM setting.  This will fail if either we didn't
    // set that, or, if we don't have access).
    SavedRegistryEntry tmp_entry8( HKEY_LOCAL_MACHINE, baseKey.get(), "", shortAppName().get() );
    tmp_entry8.reset();

    // The HKCU setting is trickier.  We may have set it, but we may also have
    // removed it (see setWindowsXP(), above).  We first try to reverse the
    // setting.  If we had removed it, then this will fail.
    SavedRegistryEntry tmp_entry9( HKEY_CURRENT_USER, baseKey.get(), "", shortAppName().get() );
    tmp_entry9.reset();
    // Now, try to reverse the removal of this key.  This will fail if there is a  current
    // setting, and will only work if this key is unset, and, we have a saved value.
    SavedRegistryEntry tmp_entry10( HKEY_CURRENT_USER, baseKey.get(), "", 0 );
    tmp_entry10.reset();

    // Notify the system of the changes.
    ::SendMessageTimeout( HWND_BROADCAST,
                          WM_SETTINGCHANGE,
                          0,
                          (LPARAM)MOZ_CLIENT_BROWSER_KEY,
                          SMTO_NORMAL|SMTO_ABORTIFHUNG,
                          MOZ_HWND_BROADCAST_MSG_TIMEOUT,
                          NULL);
}

// Restore this entry and corresponding DDE entry.
nsresult ProtocolRegistryEntry::reset() {
    // Restore this entry.
    nsresult rv = SavedRegistryEntry::reset();

    // Do same for corresponding DDE entry.
    DDERegistryEntry( protocol.get() ).reset();
    // Reset icon.
    ProtocolIconRegistryEntry( protocol.get() ).reset();

    // For http:, on WindowsXP, we need to do some extra cleanup.
    if ( protocol.EqualsLiteral( "http" ) ) {
        resetWindowsXP();
    }

    return rv;
}

static DWORD deleteKey( HKEY baseKey, const char *keyName ) {
    // Make sure input subkey isn't null.
    DWORD rc;
    if ( keyName && ::strlen(keyName) ) {
        // Open subkey.
        HKEY key;
        rc = ::RegOpenKeyEx( baseKey,
                             keyName,
                             0,
                             KEY_ENUMERATE_SUB_KEYS | DELETE,
                             &key );
        // Continue till we get an error or are done.
        while ( rc == ERROR_SUCCESS ) {
            char subkeyName[_MAX_PATH];
            DWORD len = sizeof subkeyName;
            // Get first subkey name.  Note that we always get the
            // first one, then delete it.  So we need to get
            // the first one next time, also.
            rc = ::RegEnumKeyEx( key,
                                 0,
                                 subkeyName,
                                 &len,
                                 0,
                                 0,
                                 0,
                                 0 );
            if ( rc == ERROR_NO_MORE_ITEMS ) {
                // No more subkeys.  Delete the main one.
                rc = ::RegDeleteKey( baseKey, keyName );
                break;
            } else if ( rc == ERROR_SUCCESS ) {
                // Another subkey, delete it, recursively.
                rc = deleteKey( key, subkeyName );
            }
        }
        // Close the key we opened.
        ::RegCloseKey( key );
    } else {
        rc = ERROR_BADKEY;
    }
    return rc;
}

// Set the "dde" entry by deleting the main ddexec subkey
// under HKLM\Software\Classes\<protocol>\shell\open.
// We "set" the various subkeys in order to preserve useful
// information.
nsresult DDERegistryEntry::set() {
    nsresult rv = SavedRegistryEntry::set();
    rv = activate.set();
    rv = app.set();
    rv = topic.set();
    // We've saved what we can.  Now recurse through this key and
    // subkeys.  This is necessary due to the fact that
    // ::RegDeleteKey won't work on WinNT (and Win2k?) if there are
    // subkeys.
    if ( deleteKey( baseKey, keyName.get() ) != ERROR_SUCCESS ) {
        rv = NS_ERROR_FAILURE;
    }
    return rv;
}

// Reset the main (ddeexec) value but also the Application and Topic.
// We reset the app/topic even though we no longer set them.  This
// handles cases where the user installed a prior version, and then
// upgraded.
nsresult DDERegistryEntry::reset() {
    nsresult rv = SavedRegistryEntry::reset();
    rv = activate.reset();
    rv = app.reset();
    rv = topic.reset();
    return rv;
}

// Return current setting for this registry entry.
// Optionally, the caller can ask that a boolean be set to indicate whether
// the registry value is undefined.  This flag can be used to distinguish
// between not defined at all versus simply empty (both of which return an
// empty string).
nsCString RegistryEntry::currentSetting( PRBool *currentlyUndefined ) const {
    nsCString result;

    if ( currentlyUndefined ) {
        *currentlyUndefined = PR_TRUE;
    }

    HKEY   key;
    LONG   rc = ::RegOpenKey( baseKey, keyName.get(), &key );
    if ( rc == ERROR_SUCCESS ) {
        PRUnichar buffer[4096] = { 0 };
        DWORD len = sizeof buffer;
        rc = ::RegQueryValueExW( key,
             NS_ConvertASCIItoUTF16(valueNameArg()).get(), NULL, NULL,
             (LPBYTE)buffer, &len );
        if ( rc == ERROR_SUCCESS ) {
            CopyUTF16toUTF8(buffer, result);
            if ( currentlyUndefined ) {
                *currentlyUndefined = PR_FALSE; // Indicate entry is present
            }
        }
        ::RegCloseKey( key );
    }

    return result;
}

// For each file extension, map it to this entry's file type.
// Set the file type so this application opens files of that type.
nsresult FileTypeRegistryEntry::set() {
    nsresult rv = NS_OK;

    // Set file extensions.
    for ( int i = 0; NS_SUCCEEDED( rv ) && ext[i]; i++ ) {
        nsCAutoString thisExt( "Software\\Classes\\" );
        thisExt += ext[i];
        rv = SavedRegistryEntry( HKEY_LOCAL_MACHINE, thisExt.get(), "", fileType.get() ).set();
    }

    // If OK, set file type opener.
    if ( NS_SUCCEEDED( rv ) ) {
        rv = ProtocolRegistryEntry::set();

        // If we just created this file type entry, set description and default icon.
        if ( NS_SUCCEEDED( rv ) ) {
            nsCAutoString iconFileToUse( "%1" );
            nsCAutoString descKey( "Software\\Classes\\" );
            descKey += protocol;
            RegistryEntry descEntry( HKEY_LOCAL_MACHINE, descKey.get(), NULL, "" );
            if ( descEntry.currentSetting().IsEmpty() ) {
                nsCAutoString defaultDescKey( "Software\\Classes\\" );
                defaultDescKey += defDescKey;
                RegistryEntry defaultDescEntry( HKEY_LOCAL_MACHINE, defaultDescKey.get(), NULL, "" );

                descEntry.setting = defaultDescEntry.currentSetting();
                if ( descEntry.setting.IsEmpty() )
                    descEntry.setting = desc;
                descEntry.set();
            }
            nsCAutoString iconKey( "Software\\Classes\\" );
            iconKey += protocol;
            iconKey += "\\DefaultIcon";

            if ( !iconFile.Equals(iconFileToUse) ) {
            iconFileToUse = thisApplication() + NS_LITERAL_CSTRING( ",0" );

            // Check to see if there's an icon file name associated with this extension.
            // If there is, then we need to use this icon file.  If not, then we default
            // to the main app's icon.
            if ( !iconFile.IsEmpty() ) {
                nsCOMPtr<nsIFile> iconFileSpec;
                PRBool            flagExists;

                // Use the directory service to get the path to the chrome folder.  The
                // icons will be located in [chrome dir]\icons\default.
                // The abs path to the icon has to be in the short filename
                // format, else it won't work under win9x systems.
                rv = NS_GetSpecialDirectory( NS_APP_CHROME_DIR, getter_AddRefs( iconFileSpec ) );
                if ( NS_SUCCEEDED( rv ) ) {
                    iconFileSpec->AppendNative( NS_LITERAL_CSTRING( "icons" ) );
                    iconFileSpec->AppendNative( NS_LITERAL_CSTRING( "default" ) );
                    iconFileSpec->AppendNative( iconFile );

                    // Check to make sure that the icon file exists on disk.
                    iconFileSpec->Exists( &flagExists );
                    if ( flagExists ) {
                        rv = iconFileSpec->GetNativePath( iconFileToUse );
                        if ( NS_SUCCEEDED( rv ) ) {
                            TCHAR buffer[MAX_PATH];
                            DWORD len;

                            // Get the short path name (8.3) format for iconFileToUse
                            // else it won't work under win9x.
                            len = ::GetShortPathName( iconFileToUse.get(), buffer, sizeof buffer );
                            NS_ASSERTION ( (len > 0) && ( len < sizeof buffer ), "GetShortPathName failed!" );
                            iconFileToUse.Assign( buffer );
                            iconFileToUse.Append( NS_LITERAL_CSTRING( ",0" ) );
                        }
                        }
                    }
                }
            }

            RegistryEntry iconEntry( HKEY_LOCAL_MACHINE, iconKey.get(), NULL, iconFileToUse.get() );
            if( !iconEntry.currentSetting().Equals( iconFileToUse ) )
                iconEntry.set();
        }
    }

    return rv;
}

// Basically, the inverse of set().
// First, reset the opener for this entry's file type.
// Then, reset the file type associated with each extension.
nsresult FileTypeRegistryEntry::reset() {
    nsresult rv = ProtocolRegistryEntry::reset();

    for ( int i = 0; ext[ i ]; i++ ) {
        nsCAutoString thisExt( "Software\\Classes\\" );
        thisExt += ext[i];
        (void)SavedRegistryEntry( HKEY_LOCAL_MACHINE, thisExt.get(), "", fileType.get() ).reset();
    }

    return rv;
}

// Do inherited set() and also set key for edit (with -edit option).
//
// Note: We make the rash assumption that we "own" this filetype (aka "protocol").
// If we ever start commandeering some other file type then this may have to be
// rethought.  The solution is to override reset() and undo this (and make the
// "edit" entry a SavedRegistryEntry).
nsresult EditableFileTypeRegistryEntry::set() {
    nsresult rv = FileTypeRegistryEntry::set();
#ifndef MOZ_XUL_APP
    if ( NS_SUCCEEDED( rv ) ) {
        // only set this if we support "-edit" on the command-line
        nsCOMPtr<nsICmdLineHandler> editorService =
            do_GetService( "@mozilla.org/commandlinehandler/general-startup;1?type=edit", &rv );
        if ( NS_SUCCEEDED( rv) ) {
            nsCAutoString editKey( "Software\\Classes\\" );
            editKey += protocol;
            editKey += "\\shell\\edit\\command";
            nsCAutoString editor( thisApplication() );
            editor += " -edit \"%1\"";
            rv = RegistryEntry( HKEY_LOCAL_MACHINE, editKey.get(), "", editor.get() ).set();
        }
    }
#endif
    return rv;
}

// Convert current registry setting to boolean.
BoolRegistryEntry::operator PRBool() {
    return currentSetting().Equals( "1" ) ? PR_TRUE : PR_FALSE;
}