od_autodetect()

Attempts to determine the remote terminal's ANSI and RIP capabilities.

Synopsis

void od_autodetect(INT nFlags);

Description

Most BBS door-information files report the caller's terminal capabilities, so most doors do not need to call od_autodetect(). It is provided for sessions in which that information is unavailable or unreliable.

The function tests ANSI first by sending the ANSI cursor-position query ESC [ 6 n, followed by carriage return and spaces used to erase the query from ordinary terminals. It waits up to 660 milliseconds for a response which begins with ESC [.

It then tests RIP by sending carriage return, ESC [ !, and another carriage return with erasing spaces. It waits up to 660 milliseconds for the characters RIP, without regard to case, and discards the following eleven identification bytes when that response is found. Each test is made only if the corresponding capability is not already enabled.

Successful ANSI detection sets od_control.user_ansi to TRUE. Successful RIP detection sets od_control.user_rip to TRUE. A failed or unanswered query does not clear either field: many capable terminal programs do not implement these queries, so failure is not evidence that the mode is unavailable.

In local mode, indicated by a zero od_control.baud, OpenDoors enables ANSI and returns without sending either query. The function cannot detect AVATAR because there is no corresponding standard query; it never changes od_control.user_avatar.

The input queue is cleared before and after each remote test. Consequently, input which was already waiting, response bytes which do not match the expected prefix, and bytes received while a test is in progress may be discarded.

nFlags is reserved and ignored by the current implementation. Pass DETECT_NORMAL, the only defined value, for compatibility with future versions.

Return value

This function returns no value. Inspect od_control.user_ansi and od_control.user_rip after the call.

Example

Because a failed probe is inconclusive, a door which depends on ANSI should still ask the caller when detection fails:

od_autodetect(DETECT_NORMAL);

if(!od_control.user_ansi)
{
    od_printf("Does your terminal support ANSI graphics? (Y/N) ");
    if(od_get_answer("YN") == 'Y')
        od_control.user_ansi = TRUE;
}

See also

od_clear_keybuffer(), Terminal and screen model, Display constants