winansi: add a routine to clear the screen bufferansi

And use it to restore the old behaviour of vi and less:  they reset
the cursor to the top of the buffer and clear it.

1 files changed, 18 insertions, 0 deletions

diff --git a/win32/winansi.c b/win32/winansi.c
index ebe831593..d61e8a2cf 100644
--- a/win32/winansi.c
+++ b/win32/winansi.c
@@ -122,7 +122,25 @@ static void erase_till_end_of_screen(void)
                 &dummy);
         FillConsoleOutputAttribute(console, plain_attr, len, sbi.dwCursorPosition,
                 &dummy);
+}
+
+void reset_screen(void)
+{
+        CONSOLE_SCREEN_BUFFER_INFO sbi;
+        COORD pos;
+        DWORD dummy, len;
 
+        if (!console)
+                return;
+
+        /* move to start of screen buffer and clear it all */
+        GetConsoleScreenBufferInfo(console, &sbi);
+        pos.X = 0;
+        pos.Y = 0;
+        SetConsoleCursorPosition(console, pos);
+        len = sbi.dwSize.X * sbi.dwSize.Y;
+        FillConsoleOutputCharacterA(console, ' ', len, pos, &dummy);
+        FillConsoleOutputAttribute(console, plain_attr, len, pos, &dummy);
 }
 
 void move_cursor_row(int n)