diff -awurd 421vanilla/src/win/wddlock.c 421noasm/src/win/wddlock.c
--- 421vanilla/src/win/wddlock.c	Fri Oct 28 06:57:00 2005
+++ 421noasm/src/win/wddlock.c	Thu Mar  1 20:48:15 2007
@@ -23,9 +23,68 @@
 #define PREFIX_E                "al-wddlock ERROR: "
 
 
+//if asm is used, this code is in asmlock.s instead
+#if defined ALLEGRO_NO_ASM || defined ALLEGRO_USE_C
+
+static void update_dirty_lines (BITMAP *bmp) {
+   int i;
+   RECT rect;
+   //the width is always the full bitmap width, because we have no 
+   //  mechanism for measuring the X range of the update
+   rect.left = 0;
+   rect.right = bmp->w;
+   for (i = 0; i < bmp->h; i++) {
+      if (wd_dirty_lines[i]) {
+         int j = i+1;
+         rect.top = i;
+         //consecutive dirty lines are combined into ranges of Y values
+         for (; wd_dirty_lines[j]; j++) ;
+         rect.bottom = j;
+         update_window(&rect);
+         i = j+1;
+      }
+   }
+}
+
+uintptr_t gfx_directx_write_bank (BITMAP *bmp, int line) {
+   if (!(bmp->id & BMP_ID_LOCKED)) 
+      gfx_directx_autolock(bmp);
+   return (uintptr_t) bmp->line[line];
+}
+
+void gfx_directx_unwrite_bank (BITMAP *bmp) {
+   if (!(bmp->id & BMP_ID_AUTOLOCK)) return;
+   gfx_directx_unlock(bmp);
+   bmp->id &= ~ BMP_ID_AUTOLOCK;
+}
+
+uintptr_t gfx_directx_write_bank_win (BITMAP *bmp, int line) {
+   wd_dirty_lines[bmp->y_ofs+line] = 1;
+   if (!(bmp->id & BMP_ID_LOCKED)) gfx_directx_autolock(bmp);
+   return (uintptr_t) bmp->line[line];
+}
+
+void gfx_directx_unwrite_bank_win (BITMAP *bmp) {
+   if (!(bmp->id & BMP_ID_AUTOLOCK)) return;
+   gfx_directx_unlock(bmp);
+   bmp->id &= ~BMP_ID_AUTOLOCK;
+   // update dirty lines: this is safe because autolocking
+   // is guaranteed to be the only level of locking.
+   // (or at least, that's what it says in asmlock.s)
+   update_dirty_lines(gfx_directx_forefront_bitmap);
+}
+
+void gfx_directx_unlock_win (BITMAP *bmp) {
+   gfx_directx_unlock(bmp);
+   // forefront_bitmap may still be locked in case of nested locking
+   if (!(gfx_directx_forefront_bitmap->id & BMP_ID_LOCKED))
+      update_dirty_lines(gfx_directx_forefront_bitmap);
+}
+#else
+//asmlock.s requires these two variables
 void (*ptr_gfx_directx_autolock) (BITMAP* bmp) = gfx_directx_autolock;
 void (*ptr_gfx_directx_unlock) (BITMAP* bmp) = gfx_directx_unlock;
-
+#endif//defined ALLEGRO_NO_ASM || defined ALLEGRO_USE_C
 
 
 /* gfx_directx_switch_out:
diff -awurd 421vanilla/src/win/wddraw.h 421noasm/src/win/wddraw.h
--- 421vanilla/src/win/wddraw.h	Sun May 15 02:54:00 2005
+++ 421noasm/src/win/wddraw.h	Thu Mar  1 20:48:15 2007
@@ -116,18 +116,23 @@
 AL_FUNC(int, set_video_mode, (int w, int h, int v_w, int v_h, int color_depth));
 
 
-/* bitmap locking (from wddlock.c and asmlock.s) */
+/* bitmap locking (from wddlock.c and wgdi.c and possibly asmlock.s) */
 AL_FUNC(void, gfx_directx_lock, (BITMAP *bmp));
 AL_FUNC(void, gfx_directx_autolock, (BITMAP* bmp));
 AL_FUNC(void, gfx_directx_unlock, (BITMAP *bmp));
 AL_FUNC(void, gfx_directx_unlock_win, (BITMAP *bmp));
 AL_FUNC(void, gfx_directx_release_lock, (BITMAP * bmp));
-AL_FUNC(void, gfx_directx_write_bank, (void));
-AL_FUNC(void, gfx_directx_unwrite_bank, (void));
-AL_FUNC(void, gfx_directx_write_bank_win, (void));
-AL_FUNC(void, gfx_directx_unwrite_bank_win, (void));
-AL_FUNCPTR(void, ptr_gfx_directx_autolock, (BITMAP* bmp));
-AL_FUNCPTR(void, ptr_gfx_directx_unlock, (BITMAP* bmp));
+AL_FUNC(uintptr_t, gfx_directx_write_bank, (BITMAP *bmp, int line));
+AL_FUNC(void,      gfx_directx_unwrite_bank, (BITMAP *bmp));
+AL_FUNC(uintptr_t, gfx_directx_write_bank_win, (BITMAP *bmp, int line));
+AL_FUNC(void,      gfx_directx_unwrite_bank_win, (BITMAP *bmp));
+AL_FUNC(void,      gfx_gdi_autolock, (struct BITMAP* bmp));
+AL_FUNC(void,      gfx_gdi_unlock, (struct BITMAP* bmp));
+AL_FUNC(uintptr_t, gfx_gdi_write_bank, (BITMAP *bmp, int line));
+AL_FUNC(void,      gfx_gdi_unwrite_bank, (BITMAP *bmp));
+/* dirty window updating (from wddwin.c, used in wddlock.c or asmlock.s) */
+AL_VAR(char *,     wd_dirty_lines);
+AL_FUNCPTR(void,   update_window,  (RECT *rect));
 
 
 /* bitmap creation (from wddbmp.c) */
diff -awurd 421vanilla/src/win/wddwin.c 421noasm/src/win/wddwin.c
--- 421vanilla/src/win/wddwin.c	Sat Dec 31 12:42:00 2005
+++ 421noasm/src/win/wddwin.c	Thu Mar  1 20:48:15 2007
@@ -25,7 +25,6 @@
 #define PREFIX_E                "al-wddwin ERROR: "
 
 
-/* exported only for asmlock.s */
 char *wd_dirty_lines = NULL;  /* used in WRITE_BANK() */
 void (*update_window) (RECT *rect) = NULL;  /* window updater */
 
diff -awurd 421vanilla/src/win/wgdi.c 421noasm/src/win/wgdi.c
--- 421vanilla/src/win/wgdi.c	Sat Jul 29 15:57:00 2006
+++ 421noasm/src/win/wgdi.c	Thu Mar  1 20:48:15 2007
@@ -32,16 +32,32 @@
 #define PREFIX_E                "al-wgdi ERROR: "
 
 
-/* function from asmlock.s */ 
-extern void gfx_gdi_write_bank(void);
-extern void gfx_gdi_unwrite_bank(void);
-
-/* exported only for asmlock.s */
 static void gfx_gdi_autolock(struct BITMAP* bmp);
 static void gfx_gdi_unlock(struct BITMAP* bmp);
+
+//this is used only in asmlock.s and this file
+char *gdi_dirty_lines = NULL; /* used in WRITE_BANK() */
+
+//if asm is used, this code is in asmlock.s instead
+#if defined ALLEGRO_NO_ASM || defined ALLEGRO_USE_C
+
+uintptr_t gfx_gdi_write_bank (BITMAP *bmp, int line) {
+   gdi_dirty_lines[bmp->y_ofs] = 1;
+   if (!(bmp->id & BMP_ID_LOCKED)) gfx_gdi_autolock(bmp);
+   return (uintptr_t) bmp->line[line];
+}
+void gfx_gdi_unwrite_bank (BITMAP *bmp) {
+   if (!(bmp->id & BMP_ID_AUTOLOCK)) return;
+   gfx_gdi_unlock(bmp);
+   bmp->id &= ~ BMP_ID_AUTOLOCK;
+}
+#else
+//asmlock.s requires these two variables
 void (*ptr_gfx_gdi_autolock) (struct BITMAP* bmp) = gfx_gdi_autolock;
 void (*ptr_gfx_gdi_unlock) (struct BITMAP* bmp) = gfx_gdi_unlock;
-char *gdi_dirty_lines = NULL; /* used in WRITE_BANK() */
+//wddraw.h, despite its name, includes the exports from asmlock.s
+#include "wddraw.h"
+#endif//defined ALLEGRO_NO_ASM || defined ALLEGRO_USE_C
 
 
 static struct BITMAP *gfx_gdi_init(int w, int h, int v_w, int v_h, int color_depth);