libbb/lineedit: scroll to cursor position on any keypress

Also improve erase_till_end_of_screen.  Based on suggestions from
GitHub user avih.

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;