New option for the bar tags: 'backdrop, <label>' will draw another image under the progressbar (only works with image and slider bars)

example:
%V(22,253,198,14,-)
%xl(a,PLAY_BAR_BACKDROP-240x320x16.bmp,0,0)
%pb(0,0,198,14,PLAY_BAR-240x320x16.bmp, backdrop, a)


git-svn-id: svn://svn.rockbox.org/rockbox/trunk@29127 a1c6a512-1295-4272-9138-f99709370657

apps/gui/scrollbar.c

@@ -192,7 +192,8 @@ void gui_bitmap_scrollbar_draw(struct screen * screen, struct bitmap *bm, int x,
     screen->set_drawmode(DRMODE_SOLID|DRMODE_INVERSEVID);
 
     /* clear pixels in progress bar */
-    screen->fillrect(x, y, width, height);
+    if ((flags&DONT_CLEAR_EXCESS) == 0)
+        screen->fillrect(x, y, width, height);
 
     screen->set_drawmode(DRMODE_SOLID);
 

apps/gui/scrollbar.h

@@ -37,6 +37,7 @@ enum orientation {
                                      color even if FOREGROUND */
     INNER_FILL_MASK   = 0x00c0,
 #endif
+    DONT_CLEAR_EXCESS = 0x0100,   /* Don't clear the entire bar area */
 };
 
 /*

apps/gui/skin_engine/skin_display.c

@@ -234,6 +234,28 @@ void draw_progressbar(struct gui_wps *gwps, int line, struct progressbar *pb)
             y += img->bm.height / 2;
         }
     }
+    
+    if (pb->backdrop)
+    {
+        struct gui_img *img = pb->backdrop;
+#if LCD_DEPTH > 1
+        if(img->bm.format == FORMAT_MONO) {
+#endif
+            display->mono_bitmap_part(img->bm.data,
+                                      0, 0, img->bm.width,
+                                      x, y, width, height);
+#if LCD_DEPTH > 1
+        } else {
+            display->transparent_bitmap_part((fb_data *)img->bm.data,
+                                             0, 0,
+                                             STRIDE(display->screen_type,
+                                             img->bm.width, img->bm.height),
+                                             x, y, width, height);
+        }
+#endif
+        flags |= DONT_CLEAR_EXCESS;
+	}
+    
     if (!pb->nobar)
     {
         if (pb->image)

apps/gui/skin_engine/skin_parser.c

@@ -601,6 +601,7 @@ static int parse_progressbar_tag(struct skin_element* element,
     pb->nobar = false;
     pb->image = NULL;
     pb->slider = NULL;
+    pb->backdrop = NULL;
     pb->invert_fill_direction = false;
     pb->horizontal = true;
     
@@ -696,6 +697,18 @@ static int parse_progressbar_tag(struct skin_element* element,
             else /* option needs the next param */
                 return -1;
         }
+        else if (!strcmp(param->data.text, "backdrop"))
+        {
+            if (curr_param+1 < element->params_count)
+            {
+                curr_param++;
+                param++;
+                pb->backdrop = find_image(param->data.text, wps_data);
+                
+            }
+            else /* option needs the next param */
+                return -1;
+        }
         else if (!strcmp(param->data.text, "vertical"))
         {
             pb->horizontal = false;
@@ -735,8 +748,7 @@ static int parse_progressbar_tag(struct skin_element* element,
             add_to_ll_chain(&wps_data->images, item);
             pb->image = img;
         }
-    }
-        
+    }    
         
     if (token->type == SKIN_TOKEN_VOLUME)
         token->type = SKIN_TOKEN_VOLUMEBAR;

apps/gui/skin_engine/wps_internals.h

@@ -111,6 +111,7 @@ struct progressbar {
     bool nobar;
     struct gui_img *slider;
     bool horizontal;
+    struct gui_img *backdrop;
 };
 #endif
 

manual/appendix/wps_tags.tex

@@ -663,9 +663,12 @@ display cycling round the defined sublines. See
   \item[vertical] -- force the bar to be drawn vertically.
   \item[invert] -- invert the draw direction (i.e. right to left, or top to
     bottom).
-  \item[slider] -- draw an preloaded image over the top of the bar so that
+  \item[slider] -- draw a preloaded image over the top of the bar so that
     the centre of the image matches the current position. This must be
     followed by the label of the desired image.
+  \item[backdrop] -- draw a preloaded image under the bar. The full
+    image will be displayed and must be the same size as the bar. 
+    This must be followed by the label of the desired image.
   \item[nofill] -- don't draw the bar, only its frame (for use with the
      ``slider'' option).
   \item[nobar] -- don't draw the bar or its frame (for use with the