[gdb/tui] Fix displaying main after resizing

A TUI src window is displaying either:
- the source for the current frame,
- the source for main, or
- the string "[ No Source Available ]".

Since commit 03893ce67b5 ("[gdb/tui] Fix resizing of terminal to 1 or 2 lines")
we're able to resize the TUI to 1 line without crashing.

I noticed that if TUI is displaying main, and we resize to 1 line (destroying
the src window) and then back to a larger terminal (reconstructing the src
window), the TUI displays "[ No Source Available ]" instead of main.

Fix this by moving the responsibility for showing main from tui_enable to
tui_source_window_base::rerender.

Tested on x86_64-linux.

Approved-By: Tom Tromey <tom@tromey.com>

1 files changed, 50 insertions, 0 deletions

diff --git a/gdb/testsuite/gdb.tui/resize-one-line.exp b/gdb/testsuite/gdb.tui/resize-one-line.exp
new file mode 100644
index 0000000..5f8847c
--- /dev/null
+++ b/gdb/testsuite/gdb.tui/resize-one-line.exp
@@ -0,0 +1,50 @@
+# Copyright 2023 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/>.
+
+# Check that when showing main (because of lack of current frame) in the src
+# window, resizing to 1 line and back doesn't change the contents of the src
+# window.
+
+tuiterm_env
+
+standard_testfile main-one-line.c
+
+if {[build_executable "failed to prepare" ${testfile} ${srcfile}] == -1} {
+    return -1
+}
+
+Term::clean_restart 24 80 $testfile
+
+if {![Term::enter_tui]} {
+    unsupported "TUI not supported"
+    return
+}
+
+# Check that we have a source box containing main.
+Term::check_box "source box" 0 0 80 15
+Term::check_region_contents "src window shows main" 0 0 80 15 "main"
+
+# Resize to a single line.
+Term::resize 1 80 0
+Term::wait_for ""
+
+# Resize back to the previous size.
+Term::resize 24 80 0
+
+# Check that we still have a source box containing main.
+with_test_prefix "after resizing" {
+    gdb_assert { [Term::wait_for_region_contents  0 0 80 15 "main"] } \
+	"src window shows main"
+}