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.

4 files changed, 25 insertions, 1 deletions

diff --git a/editors/vi.c b/editors/vi.c
index b2d185193..75ce8d396 100644
--- a/editors/vi.c
+++ b/editors/vi.c
@@ -3074,7 +3074,12 @@ static void go_bottom_and_clear_to_eol(void)
 //----- Erase from cursor to end of screen -----------------------
 static void clear_to_eos(void)
 {
+#if !ENABLE_PLATFORM_MINGW32
         write1(ESC_CLEAR2EOS);
+#else
+        /* in practice clear_to_eos() always clears the entire screen */
+        reset_screen();
+#endif
 }
 
 //----- Start standout mode ------------------------------------
diff --git a/include/mingw.h b/include/mingw.h
index 5faef41bf..555fa96b7 100644
--- a/include/mingw.h
+++ b/include/mingw.h
@@ -155,6 +155,7 @@ int mingw_pclose(FILE *fd);
  */
 
 void move_cursor_row(int n);
+void reset_screen(void);
 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/miscutils/less.c b/miscutils/less.c
index 014a649e0..cc0e20bc7 100644
--- a/miscutils/less.c
+++ b/miscutils/less.c
@@ -1068,7 +1068,7 @@ static void reinitialize(void)
                 printf("\033[999;999H" "\033[6n");
 #endif
 #if ENABLE_PLATFORM_MINGW32
-        puts(CLEAR);
+        reset_screen();
 #endif
         buffer_fill_and_print();
 }
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)