Add test case for empty TUI windows

My original intent here was to add a test case to test that empty TUI
windows re-render their contents after a resize.  However, this seems
pretty broken at the moment, so a lot of the test is actually
disabled.

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

	* lib/tuiterm.exp (Term::clean_restart): Make "executable"
	optional.
	* gdb.tui/empty.exp: New file.

gdb/testsuite/ChangeLog

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

gdb/testsuite/gdb.tui/empty.exp

@@ -0,0 +1,103 @@
+# 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 with empty windows.
+
+load_lib "tuiterm.exp"
+
+standard_testfile
+
+Term::clean_restart 24 80
+
+if {![Term::enter_tui]} {
+    unsupported "TUI not supported"
+}
+
+# Each entry describes a layout.  It has these items:
+# 1. Layout name
+# 2. Test name
+# 3. List of boxes in 80x24 mode
+# 4. List of boxes in 90x40 mode
+# 5. List of test name and text for the empty window
+set layouts {
+    {src src {{3 0 77 15}} {{3 0 87 23}}
+	{{"no source" "No Source Available"}}}
+    {regs src-regs {{0 0 80 8} {3 7 77 8}} {{0 0 90 13} {3 13 87 13}}
+	{
+	    {"no source" "No Source Available"}
+	    {"no regs" "Register Values Unavailable"}
+	}}
+    {asm asm {{3 0 77 15}} {{3 0 87 24}}
+	{"no asm" "No Assembly Available"}}
+    {regs asm-regs {{0 0 80 8} {3 7 77 9}} {{0 0 90 13} {3 13 87 14}}
+	{
+	    {"no asm" "No Assembly Available"}
+	    {"no regs" "Register Values Unavailable"}
+	}}
+    {split split {{3 0 77 8} {3 7 77 9}} {{3 0 87 14} {3 14 87 14}}
+	{
+	    {"no source" "No Source Available"}
+	    {"no asm" "No Assembly Available"}
+	}}
+    {regs split-regs {{0 0 80 8} {3 7 77 9}} {{0 0 90 13} {3 13 87 14}}
+	{
+	    {"no asm" "No Assembly Available"}
+	    {"no regs" "Register Values Unavailable"}
+	}}
+}
+
+# Helper function to verify a list of boxes.
+proc check_boxes {boxes} {
+    set boxno 1
+    foreach box $boxes {
+	if {$boxno > 1} {
+	    # The upper-left corner of the second box may not render
+	    # properly, due to overlap.
+	    setup_xfail *-*-*
+	}
+	eval Term::check_box [list "box $boxno"] $box
+	incr boxno
+    }
+}
+
+# Helper function to verify text.
+proc check_text {text_list} {
+    set text [Term::get_all_lines]
+    foreach item $text_list {
+	lassign $item testname check
+	gdb_assert {[string first $check $text]} $testname
+    }
+}
+
+foreach layout $layouts {
+    lassign $layout name testname small_boxes large_boxes text_list
+
+    with_test_prefix $testname {
+	Term::command "layout $name"
+	with_test_prefix 80x24 {
+	    check_boxes $small_boxes
+	    check_text $text_list
+	}
+
+	# FIXME: resizing is broken enough that we don't test it for
+	# now.
+	# Term::resize 40 90
+	# with_test_prefix 90x40 {
+	#     check_boxes $large_boxes
+	#     check_text $text_list
+	# }
+	# Term::resize 24 80
+    }
+}

gdb/testsuite/lib/tuiterm.exp

@@ -392,13 +392,18 @@ namespace eval Term {
 
     # Like ::clean_restart, but ensures that gdb starts in an
     # environment where the TUI can work.  ROWS and COLS are the size
-    # of the terminal.  EXECUTABLE is passed to clean_restart.
-    proc clean_restart {rows cols executable} {
+    # of the terminal.  EXECUTABLE, if given, is passed to
+    # clean_restart.
+    proc clean_restart {rows cols {executable {}}} {
 	global env stty_init
 	save_vars {env(TERM) stty_init} {
 	    setenv TERM ansi
 	    _setup $rows $cols
-	    ::clean_restart $executable
+	    if {$executable == ""} {
+		::clean_restart
+	    } else {
+		::clean_restart $executable
+	    }
 	}
     }