Add TUI resizing test

This adds a test case that resizes the terminal and then checks that
the TUI updates properly.

gdb/testsuite/ChangeLog
2019-07-27  Tom Tromey  <tom@tromey.com>

	* lib/tuiterm.exp (spawn): New proc.
	(Term::resize): New proc.
	* gdb.tui/resize.exp: New file.

gdb/testsuite/ChangeLog

@@ -1,3 +1,9 @@
+2019-07-27  Tom Tromey  <tom@tromey.com>
+
+	* lib/tuiterm.exp (spawn): New proc.
+	(Term::resize): New proc.
+	* gdb.tui/resize.exp: New file.
+
 2019-07-27  Tom Tromey  <tom@tromey.com>
 
 	* gdb.tui/list.exp: New file.

gdb/testsuite/gdb.tui/resize.exp

@@ -0,0 +1,42 @@
+# Copyright 2019 Free Software Foundation, Inc.
+
+# This program is free software; you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation; either version 3 of the License, or
+# (at your option) any later version.
+#
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+# Test TUI resizing.
+
+load_lib "tuiterm.exp"
+
+standard_testfile tui-layout.c
+
+if {[build_executable "failed to prepare" ${testfile} ${srcfile}] == -1} {
+    return -1
+}
+
+Term::clean_restart 24 80 $testfile
+
+if {![runto_main]} {
+    perror "test suppressed"
+    return
+}
+
+if {![Term::enter_tui]} {
+    unsupported "TUI not supported"
+}
+
+Term::check_contents "source at startup" ">|21 *return 0"
+
+Term::resize 40 90
+# Resizing seems to be somewhat broken.
+setup_xfail *-*-*
+Term::check_box "source box after resize" 0 0 90 23

gdb/testsuite/lib/tuiterm.exp

@@ -15,6 +15,19 @@
 
 # An ANSI terminal emulator for expect.
 
+# The expect "spawn" function puts the tty name into the spawn_out
+# array; but dejagnu doesn't export this globally.  So, we have to
+# wrap spawn with our own function, so that we can capture this value.
+# The value is later used in calls to stty.
+rename spawn builtin_spawn
+proc spawn {args} {
+    set result [uplevel builtin_spawn $args]
+    global gdb_spawn_name
+    upvar spawn_out spawn_out
+    set gdb_spawn_name $spawn_out(slave,name)
+    return $result
+}
+
 namespace eval Term {
     variable _rows
     variable _cols
@@ -523,4 +536,36 @@ namespace eval Term {
 	    verbose "$fmt [get_line $y]"
 	}
     }
+
+    # Resize the terminal.
+    proc resize {rows cols} {
+	variable _chars
+	variable _rows
+	variable _cols
+
+	set old_rows [expr {min ($_rows, $rows)}]
+	set old_cols [expr {min ($_cols, $cols)}]
+
+	# Copy locally.
+	array set local_chars [array get _chars]
+	unset _chars
+
+	set _rows $rows
+	set _cols $cols
+	_clear_lines 0 $_rows
+
+	for {set x 0} {$x < $old_cols} {incr x} {
+	    for {set y 0} {$y < $old_rows} {incr y} {
+		set _chars($x,$y) $local_chars($x,$y)
+	    }
+	}
+
+	global gdb_spawn_name
+	# Somehow the number of columns transmitted to gdb is one less
+	# than what we request from expect.  We hide this weird
+	# details from the caller.
+	stty rows $_rows columns [expr {$_cols + 1}] \
+	    < $gdb_spawn_name
+	_accept
+    }
 }