Fix behavior of backspace in multiline cmdline editing

0007-Fix-backspace-when-editing-a-multiline-cmdline.patch

@@ -0,0 +1,137 @@
+From 7ebe10128eef978e99667d741ed4588d80b38441 Mon Sep 17 00:00:00 2001
+From: Robbie Harwood <rharwood@redhat.com>
+Date: Thu, 21 Oct 2021 15:15:33 -0400
+Subject: [PATCH] Fix backspace when editing a multiline cmdline
+
+Once the cmdline had passed the width of the screen, adding additional
+characters introduced a spurious newline, and another newline at the
+width of input.  Furthermore, hitting backspace would not start
+redrawing at the end of input, but rather at the beginning of the
+current line - resulting in extra duplicate lines scrolling the console.
+
+First, fix the assumption that the length of cmdline is the width - it
+needs to include the length of the prompt (i.e., length of input and
+space).
+
+Second, fix the behavior of single-line redraw (i.e., redraw == 1) to
+move the cursor to the row the line begins at.
+
+Third, don't scroll the cursor down when a line wrap would occur - it's
+not necessary since line wrap is enabled, and results in the extra blank
+line.
+
+Finally, comment all used escape sequences so that I don't need to look
+them up again.
+
+Signed-off-by: Robbie Harwood <rharwood@redhat.com>
+---
+ com32/elflink/ldlinux/cli.c | 33 ++++++++++++++++++---------------
+ 1 file changed, 18 insertions(+), 15 deletions(-)
+
+diff --git a/com32/elflink/ldlinux/cli.c b/com32/elflink/ldlinux/cli.c
+index 3119b11f..4913f038 100644
+--- a/com32/elflink/ldlinux/cli.c
++++ b/com32/elflink/ldlinux/cli.c
+@@ -135,6 +135,7 @@ const char *edit_cmdline(const char *input, int top /*, int width */ ,
+     struct cli_command *comm_counter = NULL;
+     clock_t kbd_to = kbdtimeout;
+     clock_t tto = totaltimeout;
++    int prompt_len = 1 + strlen(input);
+ 
+     if (!width) {
+ 	int height;
+@@ -144,7 +145,7 @@ const char *edit_cmdline(const char *input, int top /*, int width */ ,
+ 
+     len = cursor = 0;
+     prev_len = 0;
+-    x = y = 0;
++    y = 0;
+ 
+     /*
+      * Before we start messing with the x,y coordinates print 'input'
+@@ -152,6 +153,7 @@ const char *edit_cmdline(const char *input, int top /*, int width */ ,
+      * previously.
+      */
+     printf("%s ", input);
++    x = prompt_len;
+ 
+     while (!done) {
+ 	if (redraw > 1) {
+@@ -162,8 +164,7 @@ const char *edit_cmdline(const char *input, int top /*, int width */ ,
+ 	    if (pDraw_Menu)
+ 		    (*pDraw_Menu) (-1, top, 1);
+ 	    prev_len = 0;
+-	    printf("\033[2J\033[H");
+-	    // printf("\033[0m\033[2J\033[H");
++	    printf("\033[2J\033[H"); /* Clear entire screen; move to 0, 0. */
+ 	}
+ 
+ 	if (redraw > 0) {
+@@ -172,10 +173,14 @@ const char *edit_cmdline(const char *input, int top /*, int width */ ,
+ 	    prev_len = max(len, prev_len);
+ 
+ 	    /* Redraw the command line */
+-	    printf("\033[?25l");
+-	    printf("\033[1G%s ", input);
++	    printf("\033[?25l"); /* Hide cursor. */
++	    printf("\033[1G"); /* Column 1. */
++	    if (y > 0)
++		printf("\033[%dA", y); /* Directly up. */
+ 
+-	    x = strlen(input);
++	    printf("%s ", input);
++
++	    x = prompt_len;
+ 	    y = 0;
+ 	    at = 0;
+ 	    while (at < prev_len) {
+@@ -183,23 +188,22 @@ const char *edit_cmdline(const char *input, int top /*, int width */ ,
+ 		at++;
+ 		x++;
+ 		if (x >= width) {
+-		    printf("\r\n");
+ 		    x = 0;
+ 		    y++;
+ 		}
+ 	    }
+-	    printf("\033[K\r");
++	    printf("\033[K\r"); /* Clear to end of line; go to beginning. */
+ 
+-	    dy = y - (cursor + strlen(input) + 1) / width;
+-	    x = (cursor + strlen(input) + 1) % width;
++	    dy = y - (cursor + prompt_len) / width;
++	    x = (cursor + prompt_len) % width;
+ 
+ 	    if (dy) {
+-		printf("\033[%dA", dy);
++		printf("\033[%dA", dy); /* Cursor directly up. */
+ 		y -= dy;
+ 	    }
+ 	    if (x)
+-		printf("\033[%dC", x);
+-	    printf("\033[?25h");
++		printf("\033[%dC", x); /* Cursor forward. */
++	    printf("\033[?25h"); /* Show cursor. */
+ 	    prev_len = len;
+ 	    redraw = 0;
+ 	}
+@@ -439,7 +443,6 @@ const char *edit_cmdline(const char *input, int top /*, int width */ ,
+ 		    cursor++;
+ 		    x++;
+ 		    if (x >= width) {
+-			printf("\r\n\033[K");
+ 			y++;
+ 			x = 0;
+ 		    }
+@@ -459,7 +462,7 @@ const char *edit_cmdline(const char *input, int top /*, int width */ ,
+ 	}
+     }
+ 
+-    printf("\033[?7h");
++    printf("\033[?7h"); /* Enable line wrap. */
+ 
+     /* Add the command to the history if its length is larger than 0 */
+     len = strlen(ret);
+-- 
+2.33.0
+

syslinux.spec

@@ -7,7 +7,7 @@ Summary: Simple kernel loader which boots from a FAT filesystem
 Name: syslinux
 Version: 6.04
 %define tarball_version 6.04-pre1
-Release: 0.19%{?dist}
+Release: 0.20%{?dist}
 License: GPLv2+
 URL: http://syslinux.zytor.com/wiki/index.php/The_Syslinux_Project
 Source0: http://www.kernel.org/pub/linux/utils/boot/syslinux/%{name}-%{tarball_version}.tar.xz
@@ -17,6 +17,7 @@ Patch0003: 0003-include-sysmacros-h.patch
 Patch0004: 0004-Add-RPMOPTFLAGS-to-CFLAGS-for-some-stuff.patch
 Patch0005: 0005-Workaround-multiple-definition-of-symbol-errors.patch
 Patch0006: 0006-Replace-builtin-strlen-that-appears-to-get-optimized.patch
+Patch0007: 0007-Fix-backspace-when-editing-a-multiline-cmdline.patch
 
 # this is to keep rpmbuild from thinking the .c32 / .com / .0 / memdisk files
 # in noarch packages are a reason to stop the build.
@@ -256,6 +257,9 @@ fi
 %endif
 
 %changelog
+* Thu Oct 21 2021 Robbie Harwood <rharwood@redhat.com> - 6.04-0.20
+- Fix behavior of backspace in multiline cmdline editing
+
 * Wed Sep 01 2021 Robbie Harwood <rharwood@redhat.com> - 6.04-0.19
 - Place extlinux(1) in the extlinux subpackage
 - Resolves: #977004