wine-eac/server/winstation.c

/*
 * Server-side window stations and desktops handling
 *
 * Copyright (C) 2002, 2005 Alexandre Julliard
 *
 * This library is free software; you can redistribute it and/or
 * modify it under the terms of the GNU Lesser General Public
 * License as published by the Free Software Foundation; either
 * version 2.1 of the License, or (at your option) any later version.
 *
 * This library is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 * Lesser General Public License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public
 * License along with this library; if not, write to the Free Software
 * Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301, USA
 */

#include "config.h"
#include "wine/port.h"

#include <stdio.h>
#include <stdarg.h>

#include "ntstatus.h"
#define WIN32_NO_STATUS
#include "windef.h"
#include "winbase.h"
#include "winuser.h"
#include "winternl.h"

#include "object.h"
#include "handle.h"
#include "request.h"
#include "process.h"
#include "user.h"
#include "file.h"
#include "security.h"
#include "unicode.h"


static struct list winstation_list = LIST_INIT(winstation_list);

static void winstation_dump( struct object *obj, int verbose );
static struct object_type *winstation_get_type( struct object *obj );
static int winstation_close_handle( struct object *obj, struct process *process, obj_handle_t handle );
static struct object *winstation_lookup_name( struct object *obj, struct unicode_str *name,
                                              unsigned int attr );
static void winstation_destroy( struct object *obj );
static unsigned int winstation_map_access( struct object *obj, unsigned int access );
static void desktop_dump( struct object *obj, int verbose );
static struct object_type *desktop_get_type( struct object *obj );
static int desktop_link_name( struct object *obj, struct object_name *name, struct object *parent );
static void desktop_alloc_handle( struct object *obj, struct process *process, obj_handle_t handle );
static int desktop_close_handle( struct object *obj, struct process *process, obj_handle_t handle );
static void desktop_destroy( struct object *obj );
static unsigned int desktop_map_access( struct object *obj, unsigned int access );

static const struct object_ops winstation_ops =
{
    sizeof(struct winstation),    /* size */
    winstation_dump,              /* dump */
    winstation_get_type,          /* get_type */
    no_add_queue,                 /* add_queue */
    NULL,                         /* remove_queue */
    NULL,                         /* signaled */
    NULL,                         /* get_esync_fd */
    NULL,                         /* satisfied */
    no_signal,                    /* signal */
    no_get_fd,                    /* get_fd */
    winstation_map_access,        /* map_access */
    default_get_sd,               /* get_sd */
    default_set_sd,               /* set_sd */
    winstation_lookup_name,       /* lookup_name */
    directory_link_name,          /* link_name */
    default_unlink_name,          /* unlink_name */
    no_open_file,                 /* open_file */
    no_kernel_obj_list,           /* get_kernel_obj_list */
    no_alloc_handle,              /* alloc_handle */
    winstation_close_handle,      /* close_handle */
    winstation_destroy            /* destroy */
};


static const struct object_ops desktop_ops =
{
    sizeof(struct desktop),       /* size */
    desktop_dump,                 /* dump */
    desktop_get_type,             /* get_type */
    no_add_queue,                 /* add_queue */
    NULL,                         /* remove_queue */
    NULL,                         /* signaled */
    NULL,                         /* get_esync_fd */
    NULL,                         /* satisfied */
    no_signal,                    /* signal */
    no_get_fd,                    /* get_fd */
    desktop_map_access,           /* map_access */
    default_get_sd,               /* get_sd */
    default_set_sd,               /* set_sd */
    no_lookup_name,               /* lookup_name */
    desktop_link_name,            /* link_name */
    default_unlink_name,          /* unlink_name */
    no_open_file,                 /* open_file */
    no_kernel_obj_list,           /* get_kernel_obj_list */
    desktop_alloc_handle,         /* alloc_handle */
    desktop_close_handle,         /* close_handle */
    desktop_destroy               /* destroy */
};

#define DESKTOP_ALL_ACCESS 0x01ff

/* create a winstation object */
static struct winstation *create_winstation( struct object *root, const struct unicode_str *name,
                                             unsigned int attr, unsigned int flags )
{
    static unsigned int id = 0x10000;
    struct winstation *winstation;
    struct unicode_str default_name;
    char buffer[32];

    if (name->len)
    {
        winstation = create_named_object( root, &winstation_ops, name, attr, NULL );
        goto done;
    }

    do
    {
        if (!++id) id = 1;  /* avoid an id of 0 */
        sprintf( buffer, "Service-0x0-%x$", id);
        ascii_to_unicode_str( buffer, &default_name );
        winstation = create_named_object( root, &winstation_ops, &default_name, attr & ~OBJ_OPENIF, NULL );
    }
    while (!winstation && get_error() == STATUS_OBJECT_NAME_COLLISION);

done:
    if (winstation)
    {
        if (get_error() != STATUS_OBJECT_NAME_EXISTS)
        {
            /* initialize it if it didn't already exist */
            winstation->flags = flags;
            winstation->clipboard = NULL;
            winstation->atom_table = NULL;
            list_add_tail( &winstation_list, &winstation->entry );
            list_init( &winstation->desktops );
            if (!(winstation->desktop_names = create_namespace( 7 )))
            {
                release_object( winstation );
                return NULL;
            }
        }
        else clear_error();
    }

    return winstation;
}

static void winstation_dump( struct object *obj, int verbose )
{
    struct winstation *winstation = (struct winstation *)obj;

    fprintf( stderr, "Winstation flags=%x clipboard=%p atoms=%p\n",
             winstation->flags, winstation->clipboard, winstation->atom_table );
}

static struct object_type *winstation_get_type( struct object *obj )
{
    static const struct unicode_str str = { type_WindowStation, sizeof(type_WindowStation) };
    return get_object_type( &str );
}

static int winstation_close_handle( struct object *obj, struct process *process, obj_handle_t handle )
{
    return (process->winstation != handle);
}

static struct object *winstation_lookup_name( struct object *obj, struct unicode_str *name,
                                              unsigned int attr )
{
    struct winstation *winstation = (struct winstation *)obj;
    struct object *found;

    assert( obj->ops == &winstation_ops );

    if (!name) return NULL;  /* open the winstation itself */

    if (get_path_element( name->str, name->len ) < name->len)  /* no backslash allowed in name */
    {
        set_error( STATUS_OBJECT_PATH_SYNTAX_BAD );
        return NULL;
    }

    if ((found = find_object( winstation->desktop_names, name, attr )))
        name->len = 0;

    return found;
}

static void winstation_destroy( struct object *obj )
{
    struct winstation *winstation = (struct winstation *)obj;

    list_remove( &winstation->entry );
    if (winstation->clipboard) release_object( winstation->clipboard );
    if (winstation->atom_table) release_object( winstation->atom_table );
    free( winstation->desktop_names );
}

static unsigned int winstation_map_access( struct object *obj, unsigned int access )
{
    if (access & GENERIC_READ)    access |= STANDARD_RIGHTS_READ | WINSTA_ENUMDESKTOPS | WINSTA_READATTRIBUTES |
                                            WINSTA_ENUMERATE | WINSTA_READSCREEN;
    if (access & GENERIC_WRITE)   access |= STANDARD_RIGHTS_WRITE | WINSTA_ACCESSCLIPBOARD | WINSTA_CREATEDESKTOP |
                                            WINSTA_WRITEATTRIBUTES;
    if (access & GENERIC_EXECUTE) access |= STANDARD_RIGHTS_EXECUTE | WINSTA_ACCESSGLOBALATOMS | WINSTA_EXITWINDOWS;
    if (access & GENERIC_ALL)     access |= STANDARD_RIGHTS_REQUIRED | WINSTA_ALL_ACCESS;
    return access & ~(GENERIC_READ | GENERIC_WRITE | GENERIC_EXECUTE | GENERIC_ALL);
}

/* retrieve the process window station, checking the handle access rights */
struct winstation *get_process_winstation( struct process *process, unsigned int access )
{
    return (struct winstation *)get_handle_obj( process, process->winstation,
                                                access, &winstation_ops );
}

/* retrieve a pointer to a desktop object */
struct desktop *get_desktop_obj( struct process *process, obj_handle_t handle, unsigned int access )
{
    return (struct desktop *)get_handle_obj( process, handle, access, &desktop_ops );
}

/* create a desktop object */
static struct desktop *create_desktop( const struct unicode_str *name, unsigned int attr,
                                       unsigned int flags, struct winstation *winstation )
{
    struct desktop *desktop;

    if ((desktop = create_named_object( &winstation->obj, &desktop_ops, name, attr, NULL )))
    {
        if (get_error() != STATUS_OBJECT_NAME_EXISTS)
        {
            /* initialize it if it didn't already exist */
            desktop->flags = flags;
            desktop->winstation = (struct winstation *)grab_object( winstation );
            desktop->top_window = NULL;
            desktop->msg_window = NULL;
            desktop->global_hooks = NULL;
            desktop->close_timeout = NULL;
            desktop->foreground_input = NULL;
            desktop->users = 0;
            memset( &desktop->cursor, 0, sizeof(desktop->cursor) );
            memset( desktop->keystate, 0, sizeof(desktop->keystate) );
            list_add_tail( &winstation->desktops, &desktop->entry );
            list_init( &desktop->hotkeys );
        }
        else clear_error();
    }
    return desktop;
}

static void desktop_dump( struct object *obj, int verbose )
{
    struct desktop *desktop = (struct desktop *)obj;

    fprintf( stderr, "Desktop flags=%x winstation=%p top_win=%p hooks=%p\n",
             desktop->flags, desktop->winstation, desktop->top_window, desktop->global_hooks );
}

static struct object_type *desktop_get_type( struct object *obj )
{
    static const struct unicode_str str = { type_Desktop, sizeof(type_Desktop) };
    return get_object_type( &str );
}

static int desktop_link_name( struct object *obj, struct object_name *name, struct object *parent )
{
    struct winstation *winstation = (struct winstation *)parent;

    if (parent->ops != &winstation_ops)
    {
        set_error( STATUS_OBJECT_TYPE_MISMATCH );
        return 0;
    }
    if (get_path_element( name->name, name->len ) < name->len)  /* no backslash allowed in name */
    {
        set_error( STATUS_OBJECT_PATH_SYNTAX_BAD );
        return 0;
    }
    namespace_add( winstation->desktop_names, name );
    return 1;
}

static void close_desktop_timeout( void *private )
{
    struct desktop *desktop = private;

    desktop->close_timeout = NULL;
    unlink_named_object( &desktop->obj );  /* make sure no other process can open it */
    post_desktop_message( desktop, WM_CLOSE, 0, 0 );  /* and signal the owner to quit */
}

/* remove a user of the desktop and start the close timeout if necessary */
static void remove_desktop_user( struct desktop *desktop )
{
    assert( desktop->users > 0 );
    desktop->users--;

    if (!desktop->users && get_top_window_owner( desktop ))
    {
        assert( !desktop->close_timeout );
        desktop->close_timeout = add_timeout_user( -TICKS_PER_SEC, close_desktop_timeout, desktop );
    }
}

static void desktop_alloc_handle( struct object *obj, struct process *process, obj_handle_t handle )
{
    struct desktop *desktop = (struct desktop *)obj;
    if (process->is_system) return;

    desktop->users++;
    if (desktop->close_timeout)
    {
        remove_timeout_user( desktop->close_timeout );
        desktop->close_timeout = NULL;
    }
}

static int desktop_close_handle( struct object *obj, struct process *process, obj_handle_t handle )
{
    struct desktop *desktop = (struct desktop *)obj;
    struct thread *thread;

    /* check if the handle is currently used by the process or one of its threads */
    if (process->desktop == handle) return 0;
    LIST_FOR_EACH_ENTRY( thread, &process->thread_list, struct thread, proc_entry )
        if (thread->desktop == handle) return 0;

    if (!process->is_system)
        remove_desktop_user( desktop );

    return 1;
}

static void desktop_destroy( struct object *obj )
{
    struct desktop *desktop = (struct desktop *)obj;

    assert( !desktop->users );
    free_hotkeys( desktop, 0 );
    if (desktop->top_window) destroy_window( desktop->top_window );
    if (desktop->msg_window) destroy_window( desktop->msg_window );
    if (desktop->global_hooks) release_object( desktop->global_hooks );
    if (desktop->close_timeout) remove_timeout_user( desktop->close_timeout );
    list_remove( &desktop->entry );
    release_object( desktop->winstation );
}

static unsigned int desktop_map_access( struct object *obj, unsigned int access )
{
    if (access & GENERIC_READ)    access |= STANDARD_RIGHTS_READ | DESKTOP_READOBJECTS | DESKTOP_ENUMERATE;
    if (access & GENERIC_WRITE)   access |= STANDARD_RIGHTS_WRITE | DESKTOP_CREATEMENU | DESKTOP_CREATEWINDOW |
                                            DESKTOP_HOOKCONTROL | DESKTOP_JOURNALRECORD | DESKTOP_JOURNALPLAYBACK |
                                            DESKTOP_WRITEOBJECTS;
    if (access & GENERIC_EXECUTE) access |= STANDARD_RIGHTS_EXECUTE | DESKTOP_SWITCHDESKTOP;
    if (access & GENERIC_ALL)     access |= STANDARD_RIGHTS_REQUIRED | DESKTOP_ALL_ACCESS;
    return access & ~(GENERIC_READ | GENERIC_WRITE | GENERIC_EXECUTE | GENERIC_ALL);
}

/* retrieve the thread desktop, checking the handle access rights */
struct desktop *get_thread_desktop( struct thread *thread, unsigned int access )
{
    return get_desktop_obj( thread->process, thread->desktop, access );
}

/* set the process default desktop handle */
void set_process_default_desktop( struct process *process, struct desktop *desktop,
                                  obj_handle_t handle )
{
    struct thread *thread;
    struct desktop *old_desktop;

    if (process->desktop == handle) return;  /* nothing to do */

    if (!(old_desktop = get_desktop_obj( process, process->desktop, 0 ))) clear_error();
    process->desktop = handle;

    /* set desktop for threads that don't have one yet */
    LIST_FOR_EACH_ENTRY( thread, &process->thread_list, struct thread, proc_entry )
        if (!thread->desktop) thread->desktop = handle;

    if (old_desktop) release_object( old_desktop );
}

/* connect a process to its window station */
void connect_process_winstation( struct process *process, struct thread *parent_thread,
                                 struct process *parent_process )
{
    struct winstation *winstation = NULL;
    struct desktop *desktop = NULL;
    obj_handle_t handle;

    /* check for an inherited winstation handle (don't ask...) */
    if ((handle = find_inherited_handle( process, &winstation_ops )))
    {
        winstation = (struct winstation *)get_handle_obj( process, handle, 0, &winstation_ops );
    }
    else if (parent_process->winstation)
    {
        handle = duplicate_handle( parent_process, parent_process->winstation,
                                   process, 0, 0, DUP_HANDLE_SAME_ACCESS );
        winstation = (struct winstation *)get_handle_obj( process, handle, 0, &winstation_ops );
    }
    if (!winstation) goto done;
    process->winstation = handle;

    if ((handle = find_inherited_handle( process, &desktop_ops )))
    {
        desktop = get_desktop_obj( process, handle, 0 );
        if (!desktop || desktop->winstation != winstation) goto done;
    }
    else
    {
        if (parent_thread && parent_thread->desktop)
            handle = parent_thread->desktop;
        else if (parent_process->desktop)
            handle = parent_process->desktop;
        else
            goto done;

        desktop = get_desktop_obj( parent_process, handle, 0 );

        if (!desktop || desktop->winstation != winstation) goto done;

        handle = duplicate_handle( parent_process, handle, process, 0, 0, DUP_HANDLE_SAME_ACCESS );
    }
    if (handle) set_process_default_desktop( process, desktop, handle );

done:
    if (desktop) release_object( desktop );
    if (winstation) release_object( winstation );
    clear_error();
}

/* close the desktop of a given process */
void close_process_desktop( struct process *process )
{
    struct desktop *desktop;
    unsigned int i = 0;
    while (enumerate_handles( process, &desktop_ops, &i, (struct object **)&desktop ))
    {
        remove_desktop_user( desktop );
        release_object( desktop );
    }
    clear_error();  /* ignore errors */
}

/* close the desktop of a given thread */
void close_thread_desktop( struct thread *thread )
{
    obj_handle_t handle = thread->desktop;

    thread->desktop = 0;
    if (handle) close_handle( thread->process, handle );
}

/* create a window station */
DECL_HANDLER(create_winstation)
{
    struct winstation *winstation;
    struct unicode_str name = get_req_unicode_str();
    struct object *root = NULL;

    reply->handle = 0;
    if (req->rootdir && !(root = get_directory_obj( current->process, req->rootdir ))) return;

    if ((winstation = create_winstation( root, &name, req->attributes, req->flags )))
    {
        reply->handle = alloc_handle( current->process, winstation, req->access, req->attributes );
        release_object( winstation );
    }
    if (root) release_object( root );
}

/* open a handle to a window station */
DECL_HANDLER(open_winstation)
{
    struct unicode_str name = get_req_unicode_str();

    reply->handle = open_object( current->process, req->rootdir, req->access,
                                 &winstation_ops, &name, req->attributes );
}


/* close a window station */
DECL_HANDLER(close_winstation)
{
    struct winstation *winstation;

    if ((winstation = (struct winstation *)get_handle_obj( current->process, req->handle,
                                                           0, &winstation_ops )))
    {
        if (close_handle( current->process, req->handle )) set_error( STATUS_ACCESS_DENIED );
        release_object( winstation );
    }
}


/* get the process current window station */
DECL_HANDLER(get_process_winstation)
{
    reply->handle = current->process->winstation;
}


/* set the process current window station */
DECL_HANDLER(set_process_winstation)
{
    struct winstation *winstation;

    if ((winstation = (struct winstation *)get_handle_obj( current->process, req->handle,
                                                           0, &winstation_ops )))
    {
        /* FIXME: should we close the old one? */
        current->process->winstation = req->handle;
        release_object( winstation );
    }
}

/* create a desktop */
DECL_HANDLER(create_desktop)
{
    struct desktop *desktop;
    struct winstation *winstation;
    struct unicode_str name = get_req_unicode_str();

    reply->handle = 0;
    if ((winstation = get_process_winstation( current->process, WINSTA_CREATEDESKTOP )))
    {
        if ((desktop = create_desktop( &name, req->attributes, req->flags, winstation )))
        {
            reply->handle = alloc_handle( current->process, desktop, req->access, req->attributes );
            release_object( desktop );
        }
        release_object( winstation );
    }
}

/* open a handle to a desktop */
DECL_HANDLER(open_desktop)
{
    struct winstation *winstation;
    struct object *obj;
    struct unicode_str name = get_req_unicode_str();

    /* FIXME: check access rights */
    if (!req->winsta)
        winstation = get_process_winstation( current->process, 0 );
    else
        winstation = (struct winstation *)get_handle_obj( current->process, req->winsta, 0, &winstation_ops );

    if (!winstation) return;

    if ((obj = open_named_object( &winstation->obj, &desktop_ops, &name, req->attributes )))
    {
        reply->handle = alloc_handle( current->process, obj, req->access, req->attributes );
        release_object( obj );
    }

    release_object( winstation );
}

/* open a handle to current input desktop */
DECL_HANDLER(open_input_desktop)
{
    /* FIXME: check access rights */
    struct winstation *winstation = get_process_winstation( current->process, 0 );
    struct desktop *desktop;

    if (!winstation) return;

    if (!(winstation->flags & WSF_VISIBLE))
    {
        set_error( STATUS_ILLEGAL_FUNCTION );
        release_object( winstation );
        return;
    }

    if ((desktop = get_desktop_obj( current->process, current->process->desktop, 0 )))
    {
        reply->handle = alloc_handle( current->process, desktop, req->access, req->attributes );
        release_object( desktop );
    }
    release_object( winstation );
}

/* close a desktop */
DECL_HANDLER(close_desktop)
{
    struct desktop *desktop;

    /* make sure it is a desktop handle */
    if ((desktop = (struct desktop *)get_handle_obj( current->process, req->handle,
                                                     0, &desktop_ops )))
    {
        if (close_handle( current->process, req->handle )) set_error( STATUS_DEVICE_BUSY );
        release_object( desktop );
    }
}


/* get the thread current desktop */
DECL_HANDLER(get_thread_desktop)
{
    struct thread *thread;

    if (!(thread = get_thread_from_id( req->tid ))) return;
    reply->handle = thread->desktop;
    release_object( thread );
}


/* set the thread current desktop */
DECL_HANDLER(set_thread_desktop)
{
    struct desktop *old_desktop, *new_desktop;
    struct winstation *winstation;

    if (!(winstation = get_process_winstation( current->process, 0 /* FIXME: access rights? */ )))
        return;

    if (!(new_desktop = get_desktop_obj( current->process, req->handle, 0 )))
    {
        release_object( winstation );
        return;
    }
    if (new_desktop->winstation != winstation)
    {
        set_error( STATUS_ACCESS_DENIED );
        release_object( new_desktop );
        release_object( winstation );
        return;
    }

    /* check if we are changing to a new desktop */

    if (!(old_desktop = get_desktop_obj( current->process, current->desktop, 0)))
        clear_error();  /* ignore error */

    /* when changing desktop, we can't have any users on the current one */
    if (old_desktop != new_desktop && current->desktop_users > 0)
        set_error( STATUS_DEVICE_BUSY );
    else
        current->desktop = req->handle;  /* FIXME: should we close the old one? */

    if (!current->process->desktop)
        set_process_default_desktop( current->process, new_desktop, req->handle );

    if (old_desktop != new_desktop && current->queue) detach_thread_input( current );

    if (old_desktop) release_object( old_desktop );
    release_object( new_desktop );
    release_object( winstation );
}


/* get/set information about a user object (window station or desktop) */
DECL_HANDLER(set_user_object_info)
{
    struct object *obj;
    data_size_t len;

    if (!(obj = get_handle_obj( current->process, req->handle, 0, NULL ))) return;

    if (obj->ops == &desktop_ops)
    {
        struct desktop *desktop = (struct desktop *)obj;
        reply->is_desktop = 1;
        reply->old_obj_flags = desktop->flags;
        if (req->flags & SET_USER_OBJECT_SET_FLAGS) desktop->flags = req->obj_flags;
    }
    else if (obj->ops == &winstation_ops)
    {
        struct winstation *winstation = (struct winstation *)obj;
        reply->is_desktop = 0;
        reply->old_obj_flags = winstation->flags;
        if (req->flags & SET_USER_OBJECT_SET_FLAGS) winstation->flags = req->obj_flags;
    }
    else
    {
        set_error( STATUS_OBJECT_TYPE_MISMATCH );
        release_object( obj );
        return;
    }
    if (obj->ops == &desktop_ops && get_reply_max_size() && (req->flags & SET_USER_OBJECT_GET_FULL_NAME))
    {
        struct desktop *desktop = (struct desktop *)obj;
        data_size_t winstation_len, desktop_len;
        const WCHAR *winstation_name = get_object_name( &desktop->winstation->obj, &winstation_len );
        const WCHAR *desktop_name = get_object_name( obj, &desktop_len );
        WCHAR *full_name;

        if (!winstation_name) winstation_len = 0;
        if (!desktop_name) desktop_len = 0;
        len = winstation_len + desktop_len + sizeof(WCHAR);
        if ((full_name = mem_alloc( len )))
        {
            memcpy( full_name, winstation_name, winstation_len );
            full_name[winstation_len / sizeof(WCHAR)] = '\\';
            memcpy( full_name + winstation_len / sizeof(WCHAR) + 1, desktop_name, desktop_len );
            set_reply_data_ptr( full_name, min( len, get_reply_max_size() ));
        }
    }
    else
    {
        const WCHAR *name = get_object_name( obj, &len );
        if (name) set_reply_data( name, min( len, get_reply_max_size() ));
    }
    release_object( obj );
}


/* enumerate window stations */
DECL_HANDLER(enum_winstation)
{
    unsigned int index = 0;
    struct winstation *winsta;
    const WCHAR *name;
    data_size_t len;

    LIST_FOR_EACH_ENTRY( winsta, &winstation_list, struct winstation, entry )
    {
        unsigned int access = WINSTA_ENUMERATE;
        if (req->index > index++) continue;
        if (!check_object_access( &winsta->obj, &access )) continue;
        clear_error();
        reply->next = index;
        if ((name = get_object_name( &winsta->obj, &len )))
            set_reply_data( name, min( len, get_reply_max_size() ));
        return;
    }
    set_error( STATUS_NO_MORE_ENTRIES );
}


/* enumerate desktops */
DECL_HANDLER(enum_desktop)
{
    struct winstation *winstation;
    struct desktop *desktop;
    unsigned int index = 0;
    const WCHAR *name;
    data_size_t len;

    if (!(winstation = (struct winstation *)get_handle_obj( current->process, req->winstation,
                                                            WINSTA_ENUMDESKTOPS, &winstation_ops )))
        return;

    LIST_FOR_EACH_ENTRY( desktop, &winstation->desktops, struct desktop, entry )
    {
        unsigned int access = DESKTOP_ENUMERATE;
        if (req->index > index++) continue;
        if (!desktop->obj.name) continue;
        if (!check_object_access( &desktop->obj, &access )) continue;
        if ((name = get_object_name( &desktop->obj, &len )))
            set_reply_data( name, min( len, get_reply_max_size() ));
        release_object( winstation );
        clear_error();
        reply->next = index;
        return;
    }

    release_object( winstation );
    set_error( STATUS_NO_MORE_ENTRIES );
}