[PATCH 4/7] [gdb/testsuite] Handle auto_left_margin in tuiterm

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

The terminal capability bw (aka as auto_left_margin) controls whether a
backspace at the start of a line wraps to the last column of the previous
line.

For tuiterm, we use TERM=ansi, and on linux at least that capability is off.

Consequently the current implementation of Term::_ctl_0x08 doesn't wrap.

Add this capability in Term::_ctl_0x08, and add a unit test.

Tested on aarch64-linux.
---
 gdb/testsuite/gdb.tui/tuiterm.exp | 13 +++++++++++--
 gdb/testsuite/lib/tuiterm.exp     | 32 ++++++++++++++++++++++++++++---
 2 files changed, 40 insertions(+), 5 deletions(-)

diff --git a/gdb/testsuite/gdb.tui/tuiterm.exp b/gdb/testsuite/gdb.tui/tuiterm.exp
index 0e03bfaa8ea..e58de688ef2 100644
--- a/gdb/testsuite/gdb.tui/tuiterm.exp
+++ b/gdb/testsuite/gdb.tui/tuiterm.exp
@@ -102,7 +102,7 @@ proc test_backspace {} {
 
     Term::_move_cursor 1 2
 
-    Term::_ctl_0x08
+    Term::_ctl_0x08 0
     check "backspace one" {
 	"abcdefgh"
 	"ijklmnop"
@@ -111,13 +111,22 @@ proc test_backspace {} {
     } 0 2
 
     # Cursor should not move if it is already at column 0.
-    Term::_ctl_0x08
+    Term::_ctl_0x08 0
     check "backspace 2" {
 	"abcdefgh"
 	"ijklmnop"
 	"qrstuvwx"
 	"yz01234 "
     } 0 2
+
+    # Cursor should wrap to previous line.
+    Term::_ctl_0x08 1
+    check "backspace 3" {
+	"abcdefgh"
+	"ijklmnop"
+	"qrstuvwx"
+	"yz01234 "
+    } 7 1
 }
 
 proc test_linefeed { } {
diff --git a/gdb/testsuite/lib/tuiterm.exp b/gdb/testsuite/lib/tuiterm.exp
index 4364ff8d05c..451fccc6693 100644
--- a/gdb/testsuite/lib/tuiterm.exp
+++ b/gdb/testsuite/lib/tuiterm.exp
@@ -90,14 +90,40 @@ namespace eval Term {
     proc _ctl_0x07 {} {
     }
 
+    # Return 1 if tuiterm has the bw/auto_left_margin enabled.
+    proc _have_bw {} {
+	return 0
+    }
+
     # Backspace.
-    proc _ctl_0x08 {} {
-	_log_cur "Backspace" {
+    proc _ctl_0x08 { {bw -1} } {
+	if { $bw == -1 } {
+	    set bw [_have_bw]
+	}
+	_log_cur "Backspace, bw == $bw" {
 	    variable _cur_col
+	    variable _cur_row
+	    variable _cols
 
-	    if {$_cur_col > 0} {
+	    if { $_cur_col > 0 } {
+		# No wrapping needed.
 		incr _cur_col -1
+		return
 	    }
+
+	    if { ! $bw } {
+		# Wrapping not enabled.
+		return
+	    }
+
+	    if { $_cur_row == 0 } {
+		# Can't wrap.
+		return
+	    }
+
+	    # Wrap to previous line.
+	    set _cur_col [expr $_cols - 1]
+	    incr _cur_row -1
 	}
     }
 
-- 
2.43.0