1 03/18/85  video_utils_
 2 
 3 
 4 This subroutine provides interfaces for activating and de-activating
 5 the video system.
 6 
 7 
 8 Entry points in video_utils_:
 9    (List is generated by the help command)
10 
11 
12 :Entry: turn_on_login_channel: 03/18/85 video_utils_$turn_on_login_channel
13 
14 
15 Function: This entry removes the existing attachment of the user's
16 terminal, replacing it with the video system.  When this entry returns
17 successfully, the switch user_terminal_ is attached through tc_io_ to
18 the user's terminal.  The switch user_ i/o is attached through
19 window_io_ to a window covering the entire screen.  invoked: vertsp,
20 can, erkl, esc, red, and ctl_char.  In addition, if ^pl is set on
21 video system invocation, ^more will be set in the video system.
22 Similarly, the settings of the current erase and kill characters are
23 copied when the video system is invoked.
24 
25 
26 Syntax:
27 declare video_utils_$turn_on_login_channel entry (fixed bin (35),
28      char (*));
29 call video_utils_$turn_on_login_channel (code, reason);
30 
31 
32 Arguments:
33 code
34    is a standard system error code.  (Output)
35 reason
36    contains information about the error, if there is one.  (Output)
37    (128 characters are enough to hold any message that may be returned
38    in reason.)
39 
40 
41 Notes:  If the video system is already in service on the user's
42 terminal, the status code video_et_$wsys_invoked is returned, and the
43 value of reason is not defined.
44 
45 If the activation of the video system fails, the original attachment of
46 the terminal (through tty_) is restored, and information is returned in
47 reason and code.
48 
49 In particular, if the switch user_i/o is not currently attached through
50 tty_, the code video_et_$switch_not_attached_with_tty_ is returned.
51 This may indicate that the user has auditing or the graphic system in
52 place.  The message returned in reason advises the user to remove
53 graphics or auditing and try again.
54 
55 
56 :Entry: turn_off_login_channel: 03/18/85 video_utils_$turn_off_login_channel
57 
58 
59 Function: This entry reverses the actions of
60 video_utils_$turn_on_login_channel.  That is, it removes the window
61 attachment of user_i/o, detaches terminal control from the user's
62 terminal, and attaches user_i/o to the user's terminal via tty_.  The
63 settings of the following modes are copied when when the video system
64 is revoked: vertsp, can, erkl, esc, red, and ctl_char.  If ^more is
65 set while in the video system, ^pl mode will be set after revoking the
66 video system.  (For more details on modes, see the window_io_ I/O
67 module.) Similarly, the settings of the current erase and kill
68 characters are copied when the video system is revoked.  It is the
69 user's responsibility to detach any windows other than user_io before
70 calling this entry point
71 
72 
73 Syntax:
74 declare video_utils_$turn_off_login_channel entry (fixed bin (35));
75 call video_utils_$turn_off_login_channel (code);
76 
77 
78 Arguments:
79 code
80    is a standard system error code.  (Output) It is nonzero if and only
81    if the video system can not be removed from the user's terminal.