[PATCH] [gdb/tui] Fix displaying main after resizing

[Tom de Vries <tdevries@suse.de>]

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 a call to tui_display_main from tui_enable to
tui_apply_current_layout.

Tested on x86_64-linux.
---
 gdb/testsuite/gdb.tui/resize-one-line.exp | 50 +++++++++++++++++++++++
 gdb/tui/tui-layout.c                      |  5 ++-
 gdb/tui/tui.c                             |  2 -
 3 files changed, 54 insertions(+), 3 deletions(-)
 create mode 100644 gdb/testsuite/gdb.tui/resize-one-line.exp

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 00000000000..5f8847cb94b
--- /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"
+}
diff --git a/gdb/tui/tui-layout.c b/gdb/tui/tui-layout.c
index 85f4991c769..e1507fa25c2 100644
--- a/gdb/tui/tui-layout.c
+++ b/gdb/tui/tui-layout.c
@@ -111,7 +111,10 @@ tui_apply_current_layout (bool preserve_cmd_win_size_p)
 
   if (gdbarch == nullptr && TUI_DISASM_WIN != nullptr)
     tui_get_begin_asm_address (&gdbarch, &addr);
-  tui_update_source_windows_with_addr (gdbarch, addr);
+  if (addr == 0)
+    tui_display_main ();
+  else
+    tui_update_source_windows_with_addr (gdbarch, addr);
 }
 
 /* See tui-layout.  */
diff --git a/gdb/tui/tui.c b/gdb/tui/tui.c
index 941c65c970f..83fe343bd3d 100644
--- a/gdb/tui/tui.c
+++ b/gdb/tui/tui.c
@@ -495,8 +495,6 @@ tui_enable (void)
 
   if (deprecated_safe_get_selected_frame ())
     tui_show_frame_info (deprecated_safe_get_selected_frame ());
-  else
-    tui_display_main ();
 
   /* Install the TUI specific hooks.  This must be done after the call to
      tui_display_main so that we don't detect the symtab changed event it

base-commit: ad785961c9ee2dbe80f233cf7f6f408e678d2197
-- 
2.35.3