disable bottom line by default

Because indexing from zero may be unexpected, #151

doc/alttab.1

@@ -1,6 +1,6 @@
 .\" generated with Ronn-NG/v0.9.1
 .\" http://github.com/apjanke/ronn-ng/tree/0.9.1
-.TH "ALTTAB" "1" "March 2023" ""
+.TH "ALTTAB" "1" "July 2023" ""
 .SH "NAME"
 \fBalttab\fR \- the task switcher
 .SH "SYNOPSIS"
@@ -292,13 +292,13 @@ On release of Alt, don't switch, keep showing the switcher\. This allows for ext
 \fB\-b\fR \fINUMBER\fR
 resource: alttab\.bottomline
 .br
-default: \fI0\fR in single\-desktop mode, \fI1\fR otherwise
+default: \fI0\fR
 .IP
 Content of auxiliary line at the bottom of each tile\. \fINUMBER\fR must be between 0 and 2:
 .IP
 \fI0\fR: Empty\.
 .IP
-\fI1\fR: Desktop to which the window belongs\.
+\fI1\fR: Index of desktop to which the window belongs, starting from zero\.
 .IP
 \fI2\fR: User name\. Requires _NET_WM_PID freedesktop property and /proc file system\.
 .TP

doc/alttab.1.ronn

@@ -319,14 +319,14 @@ Your Xresources database probably already has \*background, \*foreground or \*fo
 
   * `-b` <NUMBER>:
     resource: alttab.bottomline  
-    default: <0> in single-desktop mode, <1> otherwise
+    default: <0>
 
     Content of auxiliary line at the bottom of each tile.
     <NUMBER> must be between 0 and 2:
 
       <0>: Empty.
 
-      <1>: Desktop to which the window belongs.
+      <1>: Index of desktop to which the window belongs, starting from zero.
 
       <2>: User name. Requires _NET_WM_PID freedesktop property and /proc file system.
 

src/alttab.c

@@ -509,10 +509,7 @@ static int use_args_and_xrm(int *argc, char **argv)
             die(inv, "bottomline argument range");
         break;
     case 0:
-        g.option_bottom_line =
-            (g.option_desktop == DESK_CURRENT 
-             || g.option_desktop == DESK_SPECIAL) ?
-            BL_NONE : BL_DESKTOP;
+        g.option_bottom_line = BL_NONE;
         break;
     case -1:
         die(inv, "bottomline argument");