Fix #81: GUI programs shouldn't exit on closing the parent terminal

Issue reproduction steps:

1. Spawn a GUI program e.g. open a PDF file in zathura or evince.
2. Without quitting `nnn` close the terminal.
3. Notice that the application quits too.

Can be a nagging issue if someone is not using a drop-down terminal.

Fix: detach a GUI child and start it in a new session.

There are 2 aspects to this commit:

- It fixes #81: in cases where we do not wait for a spawned child we can assume
that the child is a GUI process. We detach and spawn the child in a new session.
- It changes the behaviour to @Rahi374's suggestion in PR #40 i.e. invoke the DE
opener in F_NOWAIT mode.

1 files changed, 8 insertions, 6 deletions

diff --git a/nnn.c b/nnn.c
index 389a63a..d5d544c 100644
--- a/nnn.c
+++ b/nnn.c
@@ -248,7 +248,6 @@ static char *player;
 static char *copier;
 static char *editor;
 static char *desktop_manager;
-static char nowait = F_NOTRACE;
 static blkcnt_t ent_blocks;
 static blkcnt_t dir_blocks;
 static ulong num_files;
@@ -759,6 +758,12 @@ spawn(const char *file, const char *arg1, const char *arg2, const char *dir, uch
 			close(fd);
 		}
 
+		if (flag & F_NOWAIT) {
+			signal(SIGHUP, SIG_IGN);
+			signal(SIGPIPE, SIG_IGN);
+			setsid();
+		}
+
 		if (flag & F_SIGINT)
 			signal(SIGINT, SIG_DFL);
 		execlp(file, file, arg1, arg2, NULL);
@@ -2520,7 +2525,7 @@ nochange:
 				}
 
 				/* Invoke desktop opener as last resort */
-				spawn(utils[OPENER], newpath, NULL, NULL, nowait);
+				spawn(utils[OPENER], newpath, NULL, NULL, F_NOWAIT | F_NOTRACE);
 				continue;
 			}
 			default:
@@ -2878,7 +2883,7 @@ nochange:
 				goto nochange;
 			}
 
-			spawn(desktop_manager, path, NULL, path, F_NOTRACE | F_NOWAIT);
+			spawn(desktop_manager, path, NULL, path, F_NOWAIT | F_NOTRACE);
 			break;
 		case SEL_FSIZE:
 			cfg.sizeorder ^= 1;
@@ -3341,9 +3346,6 @@ main(int argc, char *argv[])
 	/* Get the default copier, if set */
 	copier = getenv("NNN_COPIER");
 
-	/* Get nowait flag */
-	nowait |= getenv("NNN_NOWAIT") ? F_NOWAIT : 0;
-
 	/* Enable quotes if opted */
 	if (getenv("NNN_QUOTE_ON"))
 		cfg.quote = 1;