[PATCH] [6/?] grub-core/gfxmenu/gui_list.c - sanity checks for the scrollbar

[Vladimir Testov <vladimir.testov@rosalab.ru>]

[-- Attachment #1: Type: text/plain, Size: 568 bytes --]

some needed checks so we won't see error messages during the boot process

also the patch handles rare cases: when we have too many menu entries and / or 
too small scrollbar height, the scrollbar thumb's height could be less than 
it's vertical padding (height of north slice + height of south slice). So the 
scrollbar thumb will be drawn incorrectly.

In this case we set the height of the thumb to it's vertical padding and 
recount the position of the thumb.

-- 
With best regards,
_______________________________
Vladimir Testov, ROSA Laboratory.
www.rosalab.ru

[-- Attachment #2: grub-list-scrollbar-thumb-sanity-checks.patch --]
[-- Type: text/x-patch, Size: 2866 bytes --]

diff -Naur grub-new5/grub-core/gfxmenu/gui_list.c grub-new6/grub-core/gfxmenu/gui_list.c
--- grub-new5/grub-core/gfxmenu/gui_list.c	2013-07-17 18:57:56.597740755 +0400
+++ grub-new6/grub-core/gfxmenu/gui_list.c	2013-07-17 20:07:37.664064169 +0400
@@ -148,6 +148,33 @@
                              self->theme_dir);
 
       self->need_to_recreate_scrollbar = 0;
+
+      /* Sanity checks. */
+      if (self->scrollbar_frame != 0 && self->scrollbar_thumb != 0)
+        {
+          grub_gfxmenu_box_t box = self->menu_box;
+          grub_gfxmenu_box_t frame = self->scrollbar_frame;
+          grub_gfxmenu_box_t thumb = self->scrollbar_thumb;
+          int box_vertical_pad = (box->get_top_pad (box)
+                                  + box->get_bottom_pad (box));
+          int frame_horizontal_pad = (frame->get_left_pad (frame)
+                                      + frame->get_right_pad (frame));
+          int frame_vertical_pad = (frame->get_top_pad (frame)
+                                    + frame->get_bottom_pad (frame));
+          int thumb_horizontal_pad = (thumb->get_left_pad (thumb)
+                                      + thumb->get_right_pad (thumb));
+          int thumb_vertical_pad = (thumb->get_top_pad (thumb)
+                                    + thumb->get_bottom_pad (thumb));
+          int scrollbar_height = self->bounds.height - box_vertical_pad;
+
+          if (self->scrollbar_width < frame_horizontal_pad
+                                      + thumb_horizontal_pad
+              || scrollbar_height < frame_vertical_pad + thumb_vertical_pad)
+            {
+              self->draw_scrollbar = 0;
+              return 0;
+            }
+        }
     }
 
   return (self->scrollbar_frame != 0 && self->scrollbar_thumb != 0);
@@ -228,8 +255,18 @@
   frame->set_content_size (frame,
                            scrollbar_width - frame_horizontal_pad,
                            tracklen);
-  int thumby = tracktop + tracklen * (value - min) / (max - min);
+  int thumby;
   int thumbheight = tracklen * extent / (max - min) + 1;
+  if (thumbheight >= thumb_vertical_pad)
+    {
+      thumby = tracktop + tracklen * (value - min) / (max - min);
+    }
+  else /* Rare occasion. Thumb height is too low.  */
+    {
+      thumbheight = thumb_vertical_pad;
+      thumby = tracktop + ((tracklen - thumb_vertical_pad) * (value - min)
+                           / (max - extent));
+    }
   thumb->set_content_size (thumb,
                            scrollbar_width - frame_horizontal_pad
                            - thumb_horizontal_pad,
@@ -584,7 +621,7 @@
     }
   else if (grub_strcmp (name, "scrollbar_width") == 0)
     {
-      self->scrollbar_width = grub_strtol (value, 0, 10);
+      self->scrollbar_width = grub_strtoul (value, 0, 10);
     }
   else if (grub_strcmp (name, "scrollbar") == 0)
     {