From fd476d8629d489245e18ec278d3c846ab1359eec Mon Sep 17 00:00:00 2001
From: Ron Yorston <rmy@pobox.com>
Date: Tue, 26 Apr 2016 11:12:42 +0100
Subject: libbb/lineedit: scroll to cursor position on any keypress

Also improve erase_till_end_of_screen.  Based on suggestions from
GitHub user avih.
---
 include/mingw.h  |  1 +
 libbb/lineedit.c |  8 +++++---
 win32/winansi.c  | 22 +++++++---------------
 3 files changed, 13 insertions(+), 18 deletions(-)

diff --git a/include/mingw.h b/include/mingw.h
index f30338ba8..5faef41bf 100644
--- a/include/mingw.h
+++ b/include/mingw.h
@@ -154,6 +154,7 @@ int mingw_pclose(FILE *fd);
  * ANSI emulation wrappers
  */
 
+void move_cursor_row(int n);
 int winansi_putchar(int c);
 int winansi_puts(const char *s);
 size_t winansi_fwrite(const void *ptr, size_t size, size_t nmemb, FILE *stream);
diff --git a/libbb/lineedit.c b/libbb/lineedit.c
index 37c106bd8..e7b9ddfa1 100644
--- a/libbb/lineedit.c
+++ b/libbb/lineedit.c
@@ -2440,6 +2440,11 @@ int FAST_FUNC read_line_input(line_input_t *st, const char *prompt, char *comman
 
 		fflush_all();
 		ic = ic_raw = lineedit_read_key(read_key_buffer, timeout);
+#if ENABLE_PLATFORM_MINGW32
+		/* scroll to cursor position on any keypress */
+		if (isatty(fileno(stdin)) && isatty(fileno(stdout)))
+			move_cursor_row(0);
+#endif
 
 #if ENABLE_FEATURE_REVERSE_SEARCH
  again:
@@ -2510,9 +2515,6 @@ int FAST_FUNC read_line_input(line_input_t *st, const char *prompt, char *comman
 		case CTRL('L'):
 		vi_case(CTRL('L')|VI_CMDMODE_BIT:)
 			/* Control-l -- clear screen */
-#if ENABLE_PLATFORM_MINGW32
-			printf(ESC"[0A"); /* move to current cursor postion */
-#endif
 			printf(ESC"[H"); /* cursor to top,left */
 			redraw(0, command_len - cursor);
 			break;
diff --git a/win32/winansi.c b/win32/winansi.c
index 78d5d5f5c..ebe831593 100644
--- a/win32/winansi.c
+++ b/win32/winansi.c
@@ -109,31 +109,23 @@ static void erase_in_line(void)
 static void erase_till_end_of_screen(void)
 {
 	CONSOLE_SCREEN_BUFFER_INFO sbi;
-	COORD pos;
-	DWORD dummy;
+	DWORD dummy, len;
 
 	if (!console)
 		return;
 
 	GetConsoleScreenBufferInfo(console, &sbi);
-	FillConsoleOutputCharacterA(console, ' ',
-		sbi.dwSize.X - sbi.dwCursorPosition.X, sbi.dwCursorPosition,
+	len = sbi.dwSize.X - sbi.dwCursorPosition.X +
+			sbi.dwSize.X * (sbi.srWindow.Bottom - sbi.dwCursorPosition.Y);
+
+	FillConsoleOutputCharacterA(console, ' ', len, sbi.dwCursorPosition,
 		&dummy);
-	FillConsoleOutputAttribute(console, plain_attr,
-		sbi.dwSize.X - sbi.dwCursorPosition.X, sbi.dwCursorPosition,
+	FillConsoleOutputAttribute(console, plain_attr, len, sbi.dwCursorPosition,
 		&dummy);
 
-	pos.X = 0;
-	for (pos.Y = sbi.dwCursorPosition.Y+1; pos.Y <= sbi.srWindow.Bottom;
-			pos.Y++) {
-		FillConsoleOutputCharacterA(console, ' ', sbi.dwSize.X,
-					    pos, &dummy);
-		FillConsoleOutputAttribute(console, plain_attr, sbi.dwSize.X,
-					    pos, &dummy);
-	}
 }
 
-static void move_cursor_row(int n)
+void move_cursor_row(int n)
 {
 	CONSOLE_SCREEN_BUFFER_INFO sbi;
 
-- 
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