pygrub: Allow scrolling of the list of entries

When user wants to change entry in grub2 menu in pygrub, there
may be crash of pygrub in case of editing item ('e' key).

Crash on editing is caused longer entry list in case of grub2. As entry
window is 10 lines high, it can hold only 8 entries (2 lines for border).
Adding line outside of windows high causes crash. Patch add handling
for longer lists and scrolling through them.

Signed-off-by: Miroslav Rezanina <mrezanin@redhat.com>
Committed-by: Ian Jackson <ian.jackson@eu.citrix.com>

1 files changed, 19 insertions, 4 deletions

diff --git a/tools/pygrub/src/pygrub b/tools/pygrub/src/pygrub
index a0475a30cb..2db333e9e2 100644
--- a/tools/pygrub/src/pygrub
+++ b/tools/pygrub/src/pygrub
@@ -221,6 +221,7 @@ class GrubLineEditor(curses.textpad.Textbox):
         
 
 class Grub:
+    ENTRY_WIN_LINES = 8
     def __init__(self, file, fs = None):
         self.screen = None
         self.entry_win = None
@@ -238,7 +239,7 @@ class Grub:
                 except:
                     pass # Not important if we can't use colour
             enable_cursor(False)
-            self.entry_win = curses.newwin(10, 74, 2, 1)
+            self.entry_win = curses.newwin(Grub.ENTRY_WIN_LINES + 2, 74, 2, 1)
             self.text_win = curses.newwin(10, 70, 12, 5)
             curses.def_prog_mode()
         
@@ -287,12 +288,20 @@ class Grub:
             self.text_win.noutrefresh()
 
         curline = 0
+        pos = 0
         img = copy.deepcopy(origimg)
         while 1:
             draw()
             self.entry_win.erase()
-            self.entry_win.box()
-            for idx in range(0, len(img.lines)):
+
+            rs = 0
+            re = len(img.lines)
+            idp = 1
+            if re > Grub.ENTRY_WIN_LINES:
+                rs = curline - pos
+                re = rs + Grub.ENTRY_WIN_LINES
+
+            for idx in range(rs, re):
                 # current line should be highlighted
                 if idx == curline:
                     self.entry_win.attron(curses.A_REVERSE)
@@ -302,9 +311,11 @@ class Grub:
                 if len(l) > 70:
                     l = l[:69] + ">"
                     
-                self.entry_win.addstr(idx + 1, 2, l)
+                self.entry_win.addstr(idp, 2, l)
                 if idx == curline:
                     self.entry_win.attroff(curses.A_REVERSE)
+                idp += 1
+            self.entry_win.box()
             self.entry_win.noutrefresh()
             curses.doupdate()
 
@@ -313,8 +324,12 @@ class Grub:
                 break
             elif c == curses.KEY_UP:
                 curline -= 1
+                if pos > 0:
+                    pos -= 1
             elif c == curses.KEY_DOWN:
                 curline += 1
+                if pos < Grub.ENTRY_WIN_LINES - 1:
+                    pos += 1
             elif c == ord('b'):
                 self.isdone = True
                 break