diff --git a/commands/videotest.c b/commands/videotest.c
index 6fe4b9b..8434b1f 100644
--- a/commands/videotest.c
+++ b/commands/videotest.c
@@ -34,10 +34,10 @@ grub_cmd_videotest (grub_command_t cmd __attribute__ ((unused)),
     return grub_errno;
 
   grub_video_color_t color;
-  unsigned int x;
-  unsigned int y;
-  unsigned int width;
-  unsigned int height;
+  int x;
+  int y;
+  int width;
+  int height;
   int i;
   grub_font_t sansbig;
   grub_font_t sans;
diff --git a/include/grub/fbfill.h b/include/grub/fbfill.h
index c85fa12..b60a7ba 100644
--- a/include/grub/fbfill.h
+++ b/include/grub/fbfill.h
@@ -32,10 +32,10 @@ struct grub_video_fbrender_target
 
   struct
   {
-    unsigned int x;
-    unsigned int y;
-    unsigned int width;
-    unsigned int height;
+    int x;
+    int y;
+    int width;
+    int height;
   } viewport;
 
   /* Indicates whether the data has been allocated by us and must be freed
diff --git a/include/grub/video.h b/include/grub/video.h
index 4145db4..c24b44b 100644
--- a/include/grub/video.h
+++ b/include/grub/video.h
@@ -184,11 +184,9 @@ struct grub_video_adapter
   grub_err_t (*get_palette) (unsigned int start, unsigned int count,
                              struct grub_video_palette_data *palette_data);
 
-  grub_err_t (*set_viewport) (unsigned int x, unsigned int y,
-                              unsigned int width, unsigned int height);
+  grub_err_t (*set_viewport) (int x, int y, int width, int height);
 
-  grub_err_t (*get_viewport) (unsigned int *x, unsigned int *y,
-                              unsigned int *width, unsigned int *height);
+  grub_err_t (*get_viewport) (int *x, int *y, int *width, int *height);
 
   grub_video_color_t (*map_color) (grub_uint32_t color_name);
 
@@ -203,17 +201,17 @@ struct grub_video_adapter
                              grub_uint8_t *blue, grub_uint8_t *alpha);
 
   grub_err_t (*fill_rect) (grub_video_color_t color, int x, int y,
-                           unsigned int width, unsigned int height);
+                           int width, int height);
 
   grub_err_t (*blit_bitmap) (struct grub_video_bitmap *bitmap,
                              enum grub_video_blit_operators oper,
                              int x, int y, int offset_x, int offset_y,
-                             unsigned int width, unsigned int height);
+                             int width, int height);
 
   grub_err_t (*blit_render_target) (struct grub_video_render_target *source,
                                     enum grub_video_blit_operators oper,
                                     int x, int y, int offset_x, int offset_y,
-                                    unsigned int width, unsigned int height);
+                                    int width, int height);
 
   grub_err_t (*scroll) (grub_video_color_t color, int dx, int dy);
 
@@ -258,11 +256,11 @@ grub_err_t grub_video_set_palette (unsigned int start, unsigned int count,
 grub_err_t grub_video_get_palette (unsigned int start, unsigned int count,
                                    struct grub_video_palette_data *palette_data);
 
-grub_err_t grub_video_set_viewport (unsigned int x, unsigned int y,
-                                    unsigned int width, unsigned int height);
+grub_err_t grub_video_set_viewport (int x, int y,
+                                    int width, int height);
 
-grub_err_t grub_video_get_viewport (unsigned int *x, unsigned int *y,
-                                    unsigned int *width, unsigned int *height);
+grub_err_t grub_video_get_viewport (int *x, int *y,
+                                    int *width, int *height);
 
 grub_video_color_t grub_video_map_color (grub_uint32_t color_name);
 
@@ -277,19 +275,18 @@ grub_err_t grub_video_unmap_color (grub_video_color_t color,
                                    grub_uint8_t *blue, grub_uint8_t *alpha);
 
 grub_err_t grub_video_fill_rect (grub_video_color_t color, int x, int y,
-                                 unsigned int width, unsigned int height);
+                                 int width, int height);
 
 grub_err_t grub_video_blit_bitmap (struct grub_video_bitmap *bitmap,
                                    enum grub_video_blit_operators oper,
                                    int x, int y, int offset_x, int offset_y,
-                                   unsigned int width, unsigned int height);
+                                   int width, int height);
 
 grub_err_t grub_video_blit_render_target (struct grub_video_render_target *source,
                                           enum grub_video_blit_operators oper,
                                           int x, int y,
                                           int offset_x, int offset_y,
-                                          unsigned int width,
-                                          unsigned int height);
+                                          int width, int height);
 
 grub_err_t grub_video_scroll (grub_video_color_t color, int dx, int dy);
 
diff --git a/include/grub/video_fb.h b/include/grub/video_fb.h
index 850946d..f1aa295 100644
--- a/include/grub/video_fb.h
+++ b/include/grub/video_fb.h
@@ -36,6 +36,22 @@ struct grub_video_fbblit_info;
 
 struct grub_video_fbrender_target;
 
+/* make width and height of a rectangle non-negative */
+static inline grub_err_t grub_fb_norm_rect(int *x, int *y, int *width, int *height)
+{
+  if(*width < 0)
+    {
+      *width = -*width;
+      *x -= *width - 1;
+    }
+  if(*height < 0)
+    {
+      *height = -*height;
+      *y -= *height - 1;
+    }
+  return GRUB_ERR_NONE;
+}
+
 #define GRUB_VIDEO_FBSTD_NUMCOLORS 16
 extern struct grub_video_palette_data grub_video_fbstd_colors[GRUB_VIDEO_FBSTD_NUMCOLORS];
 
@@ -55,11 +71,11 @@ grub_err_t
 grub_video_fb_set_palette (unsigned int start, unsigned int count,
 			   struct grub_video_palette_data *palette_data);
 grub_err_t
-grub_video_fb_set_viewport (unsigned int x, unsigned int y,
-			    unsigned int width, unsigned int height);
+grub_video_fb_set_viewport (int x, int y,
+			    int width, int height);
 grub_err_t
-grub_video_fb_get_viewport (unsigned int *x, unsigned int *y,
-			    unsigned int *width, unsigned int *height);
+grub_video_fb_get_viewport (int *x, int *y,
+			    int *width, int *height);
 
 grub_video_color_t
 grub_video_fb_map_color (grub_uint32_t color_name);
@@ -85,19 +101,19 @@ grub_video_fb_unmap_color_int (struct grub_video_fbblit_info * source,
 
 grub_err_t
 grub_video_fb_fill_rect (grub_video_color_t color, int x, int y,
-			 unsigned int width, unsigned int height);
+			 int width, int height);
 
 grub_err_t
 grub_video_fb_blit_bitmap (struct grub_video_bitmap *bitmap,
 			   enum grub_video_blit_operators oper, int x, int y,
 			   int offset_x, int offset_y,
-			   unsigned int width, unsigned int height);
+			   int width, int height);
 
 grub_err_t
 grub_video_fb_blit_render_target (struct grub_video_fbrender_target *source,
                                    enum grub_video_blit_operators oper,
                                    int x, int y, int offset_x, int offset_y,
-				  unsigned int width, unsigned int height);
+				  int width, int height);
 
 grub_err_t
 grub_video_fb_scroll (grub_video_color_t color, int dx, int dy);
diff --git a/video/fb/video_fb.c b/video/fb/video_fb.c
index 5f2917d..2fb108e 100644
--- a/video/fb/video_fb.c
+++ b/video/fb/video_fb.c
@@ -117,27 +117,27 @@ grub_video_fb_set_palette (unsigned int start, unsigned int count,
 }
 
 grub_err_t
-grub_video_fb_set_viewport (unsigned int x, unsigned int y,
-			    unsigned int width, unsigned int height)
+grub_video_fb_set_viewport (int x, int y, int width, int height)
 {
+  grub_fb_norm_rect(&x, &y, &width, &height);
   /* Make sure viewport is withing screen dimensions.  If viewport was set
      to be out of the region, mark its size as zero.  */
-  if (x > render_target->mode_info.width)
+  if (x > (int)render_target->mode_info.width)
     {
       x = 0;
       width = 0;
     }
 
-  if (y > render_target->mode_info.height)
+  if (y > (int)render_target->mode_info.height)
     {
       y = 0;
       height = 0;
     }
 
-  if (x + width > render_target->mode_info.width)
+  if (x + width > (int)render_target->mode_info.width)
     width = render_target->mode_info.width - x;
 
-  if (y + height > render_target->mode_info.height)
+  if (y + height > (int)render_target->mode_info.height)
     height = render_target->mode_info.height - y;
 
   render_target->viewport.x = x;
@@ -149,8 +149,7 @@ grub_video_fb_set_viewport (unsigned int x, unsigned int y,
 }
 
 grub_err_t
-grub_video_fb_get_viewport (unsigned int *x, unsigned int *y,
-			    unsigned int *width, unsigned int *height)
+grub_video_fb_get_viewport (int *x, int *y, int *width, int *height)
 {
   if (x) *x = render_target->viewport.x;
   if (y) *y = render_target->viewport.y;
@@ -399,14 +398,15 @@ grub_video_fb_unmap_color_int (struct grub_video_fbblit_info * source,
 
 grub_err_t
 grub_video_fb_fill_rect (grub_video_color_t color, int x, int y,
-			 unsigned int width, unsigned int height)
+			 int width, int height)
 {
   struct grub_video_fbblit_info target;
 
+  grub_fb_norm_rect(&x, &y, &width, &height);
   /* Make sure there is something to do.  */
-  if ((x >= (int)render_target->viewport.width) || (x + (int)width < 0))
+  if ((x >= render_target->viewport.width) || (x + width < 0))
     return GRUB_ERR_NONE;
-  if ((y >= (int)render_target->viewport.height) || (y + (int)height < 0))
+  if ((y >= render_target->viewport.height) || (y + height < 0))
     return GRUB_ERR_NONE;
 
   /* Do not allow drawing out of viewport.  */
@@ -485,7 +485,7 @@ static void
 common_blitter (struct grub_video_fbblit_info *target,
                 struct grub_video_fbblit_info *source,
                 enum grub_video_blit_operators oper, int x, int y,
-                unsigned int width, unsigned int height,
+                int width, int height,
                 int offset_x, int offset_y)
 {
   if (oper == GRUB_VIDEO_BLIT_REPLACE)
@@ -751,27 +751,34 @@ grub_err_t
 grub_video_fb_blit_bitmap (struct grub_video_bitmap *bitmap,
 			   enum grub_video_blit_operators oper, int x, int y,
 			   int offset_x, int offset_y,
-			   unsigned int width, unsigned int height)
+			   int width, int height)
 {
   struct grub_video_fbblit_info source;
   struct grub_video_fbblit_info target;
+  int src_x = offset_x;
+  int src_y = offset_y;
+
+  /* Normalize source rectangle and shift target insert point accordingly.  */
+  grub_fb_norm_rect(&offset_x, &offset_y, &width, &height);
+  x += offset_x - src_x;
+  y += offset_y - src_y;
 
   /* Make sure there is something to do.  */
   if ((width == 0) || (height == 0))
     return GRUB_ERR_NONE;
-  if ((x >= (int)render_target->viewport.width) || (x + (int)width < 0))
+  if ((x >= render_target->viewport.width) || (x + width < 0))
     return GRUB_ERR_NONE;
-  if ((y >= (int)render_target->viewport.height) || (y + (int)height < 0))
+  if ((y >= render_target->viewport.height) || (y + height < 0))
     return GRUB_ERR_NONE;
   if ((x + (int)bitmap->mode_info.width) < 0)
     return GRUB_ERR_NONE;
   if ((y + (int)bitmap->mode_info.height) < 0)
     return GRUB_ERR_NONE;
   if ((offset_x >= (int)bitmap->mode_info.width)
-      || (offset_x + (int)width < 0))
+      || (offset_x + width < 0))
     return GRUB_ERR_NONE;
   if ((offset_y >= (int)bitmap->mode_info.height)
-      || (offset_y + (int)height < 0))
+      || (offset_y + height < 0))
     return GRUB_ERR_NONE;
 
   /* If we have negative coordinates, optimize drawing to minimum.  */
@@ -809,16 +816,16 @@ grub_video_fb_blit_bitmap (struct grub_video_bitmap *bitmap,
   if ((y + height) > render_target->viewport.height)
     height = render_target->viewport.height - y;
 
-  if ((offset_x + width) > bitmap->mode_info.width)
+  if ((offset_x + width) > (int)bitmap->mode_info.width)
     width = bitmap->mode_info.width - offset_x;
-  if ((offset_y + height) > bitmap->mode_info.height)
+  if ((offset_y + height) > (int)bitmap->mode_info.height)
     height = bitmap->mode_info.height - offset_y;
 
   /* Limit drawing to source render target dimensions.  */
-  if (width > bitmap->mode_info.width)
+  if (width > (int)bitmap->mode_info.width)
     width = bitmap->mode_info.width;
 
-  if (height > bitmap->mode_info.height)
+  if (height > (int)bitmap->mode_info.height)
     height = bitmap->mode_info.height;
 
   /* Add viewport offset.  */
@@ -842,27 +849,34 @@ grub_err_t
 grub_video_fb_blit_render_target (struct grub_video_fbrender_target *source,
                                    enum grub_video_blit_operators oper,
                                    int x, int y, int offset_x, int offset_y,
-                                   unsigned int width, unsigned int height)
+                                   int width, int height)
 {
   struct grub_video_fbblit_info source_info;
   struct grub_video_fbblit_info target_info;
+  int src_x = offset_x;
+  int src_y = offset_y;
+
+  /* Normalize source rectangle and shift target insert point accordingly.  */
+  grub_fb_norm_rect(&offset_x, &offset_y, &width, &height);
+  x += offset_x - src_x;
+  y += offset_y - src_y;
 
   /* Make sure there is something to do.  */
   if ((width == 0) || (height == 0))
     return GRUB_ERR_NONE;
-  if ((x >= (int)render_target->viewport.width) || (x + (int)width < 0))
+  if ((x >= render_target->viewport.width) || (x + width < 0))
     return GRUB_ERR_NONE;
-  if ((y >= (int)render_target->viewport.height) || (y + (int)height < 0))
+  if ((y >= render_target->viewport.height) || (y + height < 0))
     return GRUB_ERR_NONE;
   if ((x + (int)source->mode_info.width) < 0)
     return GRUB_ERR_NONE;
   if ((y + (int)source->mode_info.height) < 0)
     return GRUB_ERR_NONE;
   if ((offset_x >= (int)source->mode_info.width)
-      || (offset_x + (int)width < 0))
+      || (offset_x + width < 0))
     return GRUB_ERR_NONE;
   if ((offset_y >= (int)source->mode_info.height)
-      || (offset_y + (int)height < 0))
+      || (offset_y + height < 0))
     return GRUB_ERR_NONE;
 
   /* If we have negative coordinates, optimize drawing to minimum.  */
@@ -900,16 +914,16 @@ grub_video_fb_blit_render_target (struct grub_video_fbrender_target *source,
   if ((y + height) > render_target->viewport.height)
     height = render_target->viewport.height - y;
 
-  if ((offset_x + width) > source->mode_info.width)
+  if ((offset_x + width) > (int)source->mode_info.width)
     width = source->mode_info.width - offset_x;
-  if ((offset_y + height) > source->mode_info.height)
+  if ((offset_y + height) > (int)source->mode_info.height)
     height = source->mode_info.height - offset_y;
 
   /* Limit drawing to source render target dimensions.  */
-  if (width > source->mode_info.width)
+  if (width > (int)source->mode_info.width)
     width = source->mode_info.width;
 
-  if (height > source->mode_info.height)
+  if (height > (int)source->mode_info.height)
     height = source->mode_info.height;
 
   /* Add viewport offset.  */
@@ -969,8 +983,8 @@ grub_video_fb_scroll (grub_video_color_t color, int dx, int dy)
     }
 
   /* 2. Check if there is need to copy data.  */
-  if ((grub_abs (dx) < render_target->viewport.width)
-       && (grub_abs (dy) < render_target->viewport.height))
+  if (((int)grub_abs (dx) < render_target->viewport.width)
+       && ((int)grub_abs (dy) < render_target->viewport.height))
     {
       /* 3. Move data in render target.  */
       struct grub_video_fbblit_info target;
@@ -1011,7 +1025,7 @@ grub_video_fb_scroll (grub_video_color_t color, int dx, int dy)
     grub_video_fb_fill_rect (color, 0, 0, render_target->viewport.width, dy);
   else if (dy < 0)
     {
-      if (render_target->viewport.height < grub_abs (dy))
+      if (render_target->viewport.height < (int)grub_abs (dy))
         dy = -render_target->viewport.height;
 
       grub_video_fb_fill_rect (color, 0, render_target->viewport.height + dy,
@@ -1024,7 +1038,7 @@ grub_video_fb_scroll (grub_video_color_t color, int dx, int dy)
                               dx, render_target->viewport.height);
   else if (dx < 0)
     {
-      if (render_target->viewport.width < grub_abs (dx))
+      if (render_target->viewport.width < (int)grub_abs (dx))
         dx = -render_target->viewport.width;
 
       grub_video_fb_fill_rect (color, render_target->viewport.width + dx, 0,
diff --git a/video/video.c b/video/video.c
index c1d66bd..29d760f 100644
--- a/video/video.c
+++ b/video/video.c
@@ -227,8 +227,7 @@ grub_video_get_palette (unsigned int start, unsigned int count,
 
 /* Set viewport dimensions.  */
 grub_err_t
-grub_video_set_viewport (unsigned int x, unsigned int y,
-                         unsigned int width, unsigned int height)
+grub_video_set_viewport (int x, int y, int width, int height)
 {
   if (! grub_video_adapter_active)
     return grub_error (GRUB_ERR_BAD_DEVICE, "No video mode activated");
@@ -238,8 +237,7 @@ grub_video_set_viewport (unsigned int x, unsigned int y,
 
 /* Get viewport dimensions.  */
 grub_err_t
-grub_video_get_viewport (unsigned int *x, unsigned int *y,
-                         unsigned int *width, unsigned int *height)
+grub_video_get_viewport (int *x, int *y, int *width, int *height)
 {
   if (! grub_video_adapter_active)
     return grub_error (GRUB_ERR_BAD_DEVICE, "No video mode activated");
@@ -297,7 +295,7 @@ grub_video_unmap_color (grub_video_color_t color, grub_uint8_t *red,
 /* Fill rectangle using specified color.  */
 grub_err_t
 grub_video_fill_rect (grub_video_color_t color, int x, int y,
-                      unsigned int width, unsigned int height)
+                      int width, int height)
 {
   if (! grub_video_adapter_active)
     return grub_error (GRUB_ERR_BAD_DEVICE, "No video mode activated");
@@ -310,7 +308,7 @@ grub_err_t
 grub_video_blit_bitmap (struct grub_video_bitmap *bitmap,
                         enum grub_video_blit_operators oper,
                         int x, int y, int offset_x, int offset_y,
-                        unsigned int width, unsigned int height)
+                        int width, int height)
 {
   if (! grub_video_adapter_active)
     return grub_error (GRUB_ERR_BAD_DEVICE, "No video mode activated");
@@ -325,7 +323,7 @@ grub_err_t
 grub_video_blit_render_target (struct grub_video_render_target *target,
                                enum grub_video_blit_operators oper,
                                int x, int y, int offset_x, int offset_y,
-                               unsigned int width, unsigned int height)
+                               int width, int height)
 {
   if (! grub_video_adapter_active)
     return grub_error (GRUB_ERR_BAD_DEVICE, "No video mode activated");