1 /*
2  * This library is free software; you can redistribute it and/or
3  * modify it under the terms of the GNU Lesser General Public
4  * License as published by the Free Software Foundation; either
5  * version 2.1 of the License, or (at your option) any later version.
6  *
7  * This library is distributed in the hope that it will be useful,
8  * but WITHOUT ANY WARRANTY; without even the implied warranty of
9  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
10  * Lesser General Public License for more details.
11  *
12  * You should have received a copy of the GNU Lesser General Public
13  * License along with this library; if not, write to the Free Software
14  * Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301, USA
15  */
16 
17 /*
18  * Return FALSE if no default mail client is installed.
19  */
20 static BOOL HaveDefaultMailClient(void)
21 {
22     HKEY Key;
23     DWORD Type, Size;
24     BYTE Buffer[64];
25     BOOL HasHKCUKey;
26 
27     /* We check the default value of both HKCU\Software\Clients\Mail and
28      * HKLM\Software\Clients\Mail, if one of them is present there is a default
29      * mail client. If neither of these keys is present, we might be running
30      * on an old Windows version (W95, NT4) and we assume a default mail client
31      * might be available. Only if one of the keys is present, but there is
32      * no default value do we assume there is no default client. */
33     if (RegOpenKeyExA(HKEY_CURRENT_USER, "SOFTWARE\\Clients\\Mail", 0, KEY_QUERY_VALUE, &Key) == ERROR_SUCCESS)
34     {
35         Size = sizeof(Buffer);
36         /* Any return value besides ERROR_FILE_NOT_FOUND (including success,
37            ERROR_MORE_DATA) indicates the value is present */
38         if (RegQueryValueExA(Key, NULL, NULL, &Type, Buffer, &Size) != ERROR_FILE_NOT_FOUND)
39         {
40             RegCloseKey(Key);
41             return TRUE;
42         }
43         RegCloseKey(Key);
44         HasHKCUKey = TRUE;
45     }
46     else
47         HasHKCUKey = FALSE;
48 
49     if (RegOpenKeyExA(HKEY_LOCAL_MACHINE, "SOFTWARE\\Clients\\Mail", 0, KEY_QUERY_VALUE, &Key) == ERROR_SUCCESS)
50     {
51         Size = sizeof(Buffer);
52         if (RegQueryValueExA(Key, NULL, NULL, &Type, Buffer, &Size) != ERROR_FILE_NOT_FOUND)
53         {
54             RegCloseKey(Key);
55             return TRUE;
56         }
57         RegCloseKey(Key);
58         return FALSE;
59     }
60 
61     return ! HasHKCUKey;
62 }
63