Take into account WM decorations when tiling

Not all window managers support this but they won't be any worse
off than they are now.

Build.PL

@@ -86,6 +86,7 @@ my $build = $class->new(
         'version'          => '0',
         'Tk'               => '800.022',
         'X11::Protocol'    => '0.56',
+        'X11::Protocol::WM' => '0',
         'Locale::Maketext' => 0,
         'Exception::Class' => '1.31',
         'Try::Tiny'        => 0,

Makefile.PL

@@ -24,6 +24,7 @@ WriteMakefile
                    'Tk' => '800.022',
                    'Try::Tiny' => 0,
                    'X11::Protocol' => '0.56',
+                   'X11::Protocol::WM' => 0,
                    'version' => '0'
                  },
   'INSTALLDIRS' => 'site',

lib/App/ClusterSSH.pm

@@ -27,6 +27,7 @@ require Tk::Dialog;
 require Tk::LabEntry;
 use X11::Protocol;
 use X11::Protocol::Constants qw/ Shift Mod5 ShiftMask /;
+use X11::Protocol::WM;
 use vars qw/ %keysymtocode %keycodetosym /;
 use X11::Keysyms '%keysymtocode', 'MISCELLANY', 'XKB_KEYS', '3270', 'LATIN1',
     'LATIN2', 'LATIN3', 'LATIN4', 'KATAKANA', 'ARABIC', 'CYRILLIC', 'GREEK',
@@ -887,6 +888,17 @@ sub show_console() {
     return $self;
 }
 
+# set the first argument to the second if the first is undefined
+# the equivalent of //= but works in older Perls (e.g. 5.8)
+sub slash_slash_equal(\$$) {
+
+    if (! defined(${$_[0]})) {
+        ${$_[0]} = $_[1];
+    }
+
+    return ${$_[0]};
+}
+
 # leave function def open here so we can be flexible in how it's called
 sub retile_hosts {
     my ( $self, $force ) = @_;
@@ -986,6 +998,28 @@ sub retile_hosts {
 
     $self->config->dump("noexit") if ( $self->options->debug > 1 );
 
+    # now find the size of the window decorations
+    if (! exists($self->config->{internal_terminal_wm_decoration_left})) {
+
+        # use the first window as exemplary
+        my($wid) = $servers{(keys(%servers))[0]}{wid};
+
+        if (defined($wid)) {
+            # get the WM decoration sizes
+            ($self->config->{internal_terminal_wm_decoration_left},
+                $self->config->{internal_terminal_wm_decoration_right},
+                $self->config->{internal_terminal_wm_decoration_top},
+                $self->config->{internal_terminal_wm_decoration_bottom}) =
+                    X11::Protocol::WM::get_net_frame_extents($xdisplay, $wid);
+        }
+
+        # in case the WM call failed we set some defaults
+        slash_slash_equal($self->config->{internal_terminal_wm_decoration_left}, 0);
+        slash_slash_equal($self->config->{internal_terminal_wm_decoration_right}, 0);
+        slash_slash_equal($self->config->{internal_terminal_wm_decoration_top}, 0);
+        slash_slash_equal($self->config->{internal_terminal_wm_decoration_bottom}, 0);
+    }
+
     # now we have the info, plot first window position
     my @hosts;
     my ( $current_x, $current_y, $current_row, $current_col ) = 0;
@@ -1049,14 +1083,18 @@ sub retile_hosts {
             $current_x
                 += $self->config->{terminal_reserve_left}
                 + $self->config->{terminal_reserve_right}
-                + $self->config->{internal_terminal_width};
+                + $self->config->{internal_terminal_width}
+                + $self->config->{internal_terminal_wm_decoration_left}
+                + $self->config->{internal_terminal_wm_decoration_right};
 
             $current_col += 1;
             if ( $current_col == $self->config->{internal_columns} ) {
                 $current_y
                     += $self->config->{terminal_reserve_top}
                     + $self->config->{terminal_reserve_bottom}
-                    + $self->config->{internal_terminal_height};
+                    + $self->config->{internal_terminal_height}
+                    + $self->config->{internal_terminal_wm_decoration_top}
+                    + $self->config->{internal_terminal_wm_decoration_bottom};
                 $current_x = $self->config->{screen_reserve_left}
                     + $self->config->{terminal_reserve_left};
                 $current_row++;
@@ -2239,6 +2277,11 @@ the code until this time.
 
 =item resolve_names
 
+=item slash_slash_equal
+
+An implementation of the //= operator that works on older Perls.
+slash_slash_equal($a, 0) is equivalent to $a //= 0
+
 =item retile_hosts
 
 =item run