crecord: call prevsibling() and nextsibling() directly

The 3 classes for items used in crecord (uiheader, uihunk, uihunkline) all have
prevsibling() and nextsibling() methods. The two methods are used to get the
previous/next item of the same type of the same parent element as the current
one: when `a` is a uihunkline instance, a.nextsibling() returns the next line
in this hunk (or None, if `a` is the last line).

There are also two similar methods: previtem() and nextitem(). When called with
constrainlevel=True (the default) they simply returned the result of
prevsibling()/nextsibling(). Only when called with constrainlevel=False they
did something different: they returned previous/next item regardless of its
type (so if `a` is the last line in a hunk, a.nextitem(constrainlevel=False)
could return the next hunk or the next file -- something that is not a line).

Let's simplify this logic and make code call -sibling() methods when only
siblings are needed and -item() methods when any item would do, and then remove
the constrainlevel argument from previtem() and nextitem().

mercurial/crecord.py

@@ -1,1661 +1,1645 b''
 # stuff related specifically to patch manipulation / parsing
 #
 # Copyright 2008 Mark Edgington <[e-mail]>
 #
 # This software may be used and distributed according to the terms of the
 # GNU General Public License version 2 or any later version.
 #
 # This code is based on the Mark Edgington's crecord extension.
 # (Itself based on Bryan O'Sullivan's record extension.)
 
 from __future__ import absolute_import
 
 import locale
 import os
 import re
 import signal
 import struct
 import sys
 
 from .i18n import _
 from . import (
     encoding,
     error,
     patch as patchmod,
     util,
 )
 stringio = util.stringio
 
 # This is required for ncurses to display non-ASCII characters in default user
 # locale encoding correctly.  --immerrr
 locale.setlocale(locale.LC_ALL, '')
 
 # patch comments based on the git one
 diffhelptext = _("""# To remove '-' lines, make them ' ' lines (context).
 # To remove '+' lines, delete them.
 # Lines starting with # will be removed from the patch.
 """)
 
 hunkhelptext = _("""#
 # If the patch applies cleanly, the edited hunk will immediately be
 # added to the record list. If it does not apply cleanly, a rejects file
 # will be generated. You can use that when you try again. If all lines
 # of the hunk are removed, then the edit is aborted and the hunk is left
 # unchanged.
 """)
 
 patchhelptext = _("""#
 # If the patch applies cleanly, the edited patch will immediately
 # be finalised. If it does not apply cleanly, rejects files will be
 # generated. You can use those when you try again.
 """)
 
 try:
     import curses
     import fcntl
     import termios
     curses.error
     fcntl.ioctl
     termios.TIOCGWINSZ
 except ImportError:
     # I have no idea if wcurses works with crecord...
     try:
         import wcurses as curses
         curses.error
     except ImportError:
         # wcurses is not shipped on Windows by default, or python is not
         # compiled with curses
         curses = False
 
 def checkcurses(ui):
     """Return True if the user wants to use curses
 
     This method returns True if curses is found (and that python is built with
     it) and that the user has the correct flag for the ui.
     """
     return curses and ui.interface("chunkselector") == "curses"
 
 _origstdout = sys.__stdout__ # used by gethw()
 
 class patchnode(object):
     """abstract class for patch graph nodes
     (i.e. patchroot, header, hunk, hunkline)
     """
 
     def firstchild(self):
         raise NotImplementedError("method must be implemented by subclass")
 
     def lastchild(self):
         raise NotImplementedError("method must be implemented by subclass")
 
     def allchildren(self):
         "Return a list of all of the direct children of this node"
         raise NotImplementedError("method must be implemented by subclass")
 
     def nextsibling(self):
         """
         Return the closest next item of the same type where there are no items
         of different types between the current item and this closest item.
         If no such item exists, return None.
         """
         raise NotImplementedError("method must be implemented by subclass")
 
     def prevsibling(self):
         """
         Return the closest previous item of the same type where there are no
         items of different types between the current item and this closest item.
         If no such item exists, return None.
         """
         raise NotImplementedError("method must be implemented by subclass")
 
     def parentitem(self):
         raise NotImplementedError("method must be implemented by subclass")
 
-    def nextitem(self, constrainlevel=True, skipfolded=True):
+    def nextitem(self, skipfolded=True):
         """
-        If constrainLevel == True, return the closest next item
-        of the same type where there are no items of different types between
-        the current item and this closest item.
+        Try to return the next item closest to this item, regardless of item's
+        type (header, hunk, or hunkline).
 
-        If constrainLevel == False, then try to return the next item
-        closest to this item, regardless of item's type (header, hunk, or
-        HunkLine).
-
-        If skipFolded == True, and the current item is folded, then the child
+        If skipfolded == True, and the current item is folded, then the child
         items that are hidden due to folding will be skipped when determining
         the next item.
 
         If it is not possible to get the next item, return None.
         """
         try:
             itemfolded = self.folded
         except AttributeError:
             itemfolded = False
-        if constrainlevel:
-            return self.nextsibling()
-        elif skipfolded and itemfolded:
+        if skipfolded and itemfolded:
             nextitem = self.nextsibling()
             if nextitem is None:
                 try:
                     nextitem = self.parentitem().nextsibling()
                 except AttributeError:
                     nextitem = None
             return nextitem
         else:
             # try child
             item = self.firstchild()
             if item is not None:
                 return item
 
             # else try next sibling
             item = self.nextsibling()
             if item is not None:
                 return item
 
             try:
                 # else try parent's next sibling
                 item = self.parentitem().nextsibling()
                 if item is not None:
                     return item
 
                 # else return grandparent's next sibling (or None)
                 return self.parentitem().parentitem().nextsibling()
 
             except AttributeError: # parent and/or grandparent was None
                 return None
 
-    def previtem(self, constrainlevel=True):
+    def previtem(self):
         """
-        If constrainLevel == True, return the closest previous item
-        of the same type where there are no items of different types between
-        the current item and this closest item.
-
-        If constrainLevel == False, then try to return the previous item
-        closest to this item, regardless of item's type (header, hunk, or
-        HunkLine).
+        Try to return the previous item closest to this item, regardless of
+        item's type (header, hunk, or hunkline).
 
         If it is not possible to get the previous item, return None.
         """
-        if constrainlevel:
-            return self.prevsibling()
-        else:
-            # try previous sibling's last child's last child,
-            # else try previous sibling's last child, else try previous sibling
-            prevsibling = self.prevsibling()
-            if prevsibling is not None:
-                prevsiblinglastchild = prevsibling.lastchild()
-                if ((prevsiblinglastchild is not None) and
-                    not prevsibling.folded):
-                    prevsiblinglclc = prevsiblinglastchild.lastchild()
-                    if ((prevsiblinglclc is not None) and
-                        not prevsiblinglastchild.folded):
-                        return prevsiblinglclc
-                    else:
-                        return prevsiblinglastchild
+        # try previous sibling's last child's last child,
+        # else try previous sibling's last child, else try previous sibling
+        prevsibling = self.prevsibling()
+        if prevsibling is not None:
+            prevsiblinglastchild = prevsibling.lastchild()
+            if ((prevsiblinglastchild is not None) and
+                not prevsibling.folded):
+                prevsiblinglclc = prevsiblinglastchild.lastchild()
+                if ((prevsiblinglclc is not None) and
+                    not prevsiblinglastchild.folded):
+                    return prevsiblinglclc
                 else:
-                    return prevsibling
+                    return prevsiblinglastchild
+            else:
+                return prevsibling
 
-            # try parent (or None)
-            return self.parentitem()
+        # try parent (or None)
+        return self.parentitem()
 
 class patch(patchnode, list): # todo: rename patchroot
     """
     list of header objects representing the patch.
     """
     def __init__(self, headerlist):
         self.extend(headerlist)
         # add parent patch object reference to each header
         for header in self:
             header.patch = self
 
 class uiheader(patchnode):
     """patch header
 
     xxx shouldn't we move this to mercurial/patch.py ?
     """
 
     def __init__(self, header):
         self.nonuiheader = header
         # flag to indicate whether to apply this chunk
         self.applied = True
         # flag which only affects the status display indicating if a node's
         # children are partially applied (i.e. some applied, some not).
         self.partial = False
 
         # flag to indicate whether to display as folded/unfolded to user
         self.folded = True
 
         # list of all headers in patch
         self.patch = None
 
         # flag is False if this header was ever unfolded from initial state
         self.neverunfolded = True
         self.hunks = [uihunk(h, self) for h in self.hunks]
 
     def prettystr(self):
         x = stringio()
         self.pretty(x)
         return x.getvalue()
 
     def nextsibling(self):
         numheadersinpatch = len(self.patch)
         indexofthisheader = self.patch.index(self)
 
         if indexofthisheader < numheadersinpatch - 1:
             nextheader = self.patch[indexofthisheader + 1]
             return nextheader
         else:
             return None
 
     def prevsibling(self):
         indexofthisheader = self.patch.index(self)
         if indexofthisheader > 0:
             previousheader = self.patch[indexofthisheader - 1]
             return previousheader
         else:
             return None
 
     def parentitem(self):
         """
         there is no 'real' parent item of a header that can be selected,
         so return None.
         """
         return None
 
     def firstchild(self):
         "return the first child of this item, if one exists.  otherwise None."
         if len(self.hunks) > 0:
             return self.hunks[0]
         else:
             return None
 
     def lastchild(self):
         "return the last child of this item, if one exists.  otherwise None."
         if len(self.hunks) > 0:
             return self.hunks[-1]
         else:
             return None
 
     def allchildren(self):
         "return a list of all of the direct children of this node"
         return self.hunks
 
     def __getattr__(self, name):
         return getattr(self.nonuiheader, name)
 
 class uihunkline(patchnode):
     "represents a changed line in a hunk"
     def __init__(self, linetext, hunk):
         self.linetext = linetext
         self.applied = True
         # the parent hunk to which this line belongs
         self.hunk = hunk
         # folding lines currently is not used/needed, but this flag is needed
         # in the previtem method.
         self.folded = False
 
     def prettystr(self):
         return self.linetext
 
     def nextsibling(self):
         numlinesinhunk = len(self.hunk.changedlines)
         indexofthisline = self.hunk.changedlines.index(self)
 
         if (indexofthisline < numlinesinhunk - 1):
             nextline = self.hunk.changedlines[indexofthisline + 1]
             return nextline
         else:
             return None
 
     def prevsibling(self):
         indexofthisline = self.hunk.changedlines.index(self)
         if indexofthisline > 0:
             previousline = self.hunk.changedlines[indexofthisline - 1]
             return previousline
         else:
             return None
 
     def parentitem(self):
         "return the parent to the current item"
         return self.hunk
 
     def firstchild(self):
         "return the first child of this item, if one exists.  otherwise None."
         # hunk-lines don't have children
         return None
 
     def lastchild(self):
         "return the last child of this item, if one exists.  otherwise None."
         # hunk-lines don't have children
         return None
 
 class uihunk(patchnode):
     """ui patch hunk, wraps a hunk and keep track of ui behavior """
     maxcontext = 3
 
     def __init__(self, hunk, header):
         self._hunk = hunk
         self.changedlines = [uihunkline(line, self) for line in hunk.hunk]
         self.header = header
         # used at end for detecting how many removed lines were un-applied
         self.originalremoved = self.removed
 
         # flag to indicate whether to display as folded/unfolded to user
         self.folded = True
         # flag to indicate whether to apply this chunk
         self.applied = True
         # flag which only affects the status display indicating if a node's
         # children are partially applied (i.e. some applied, some not).
         self.partial = False
 
     def nextsibling(self):
         numhunksinheader = len(self.header.hunks)
         indexofthishunk = self.header.hunks.index(self)
 
         if (indexofthishunk < numhunksinheader - 1):
             nexthunk = self.header.hunks[indexofthishunk + 1]
             return nexthunk
         else:
             return None
 
     def prevsibling(self):
         indexofthishunk = self.header.hunks.index(self)
         if indexofthishunk > 0:
             previoushunk = self.header.hunks[indexofthishunk - 1]
             return previoushunk
         else:
             return None
 
     def parentitem(self):
         "return the parent to the current item"
         return self.header
 
     def firstchild(self):
         "return the first child of this item, if one exists.  otherwise None."
         if len(self.changedlines) > 0:
             return self.changedlines[0]
         else:
             return None
 
     def lastchild(self):
         "return the last child of this item, if one exists.  otherwise None."
         if len(self.changedlines) > 0:
             return self.changedlines[-1]
         else:
             return None
 
     def allchildren(self):
         "return a list of all of the direct children of this node"
         return self.changedlines
 
     def countchanges(self):
         """changedlines -> (n+,n-)"""
         add = len([l for l in self.changedlines if l.applied
                    and l.prettystr()[0] == '+'])
         rem = len([l for l in self.changedlines if l.applied
                    and l.prettystr()[0] == '-'])
         return add, rem
 
     def getfromtoline(self):
         # calculate the number of removed lines converted to context lines
         removedconvertedtocontext = self.originalremoved - self.removed
 
         contextlen = (len(self.before) + len(self.after) +
                       removedconvertedtocontext)
         if self.after and self.after[-1] == '\\ no newline at end of file\n':
             contextlen -= 1
         fromlen = contextlen + self.removed
         tolen = contextlen + self.added
 
         # diffutils manual, section "2.2.2.2 detailed description of unified
         # format": "an empty hunk is considered to end at the line that
         # precedes the hunk."
         #
         # so, if either of hunks is empty, decrease its line start. --immerrr
         # but only do this if fromline > 0, to avoid having, e.g fromline=-1.
         fromline, toline = self.fromline, self.toline
         if fromline != 0:
             if fromlen == 0:
                 fromline -= 1
             if tolen == 0:
                 toline -= 1
 
         fromtoline = '@@ -%d,%d +%d,%d @@%s\n' % (
             fromline, fromlen, toline, tolen,
             self.proc and (' ' + self.proc))
         return fromtoline
 
     def write(self, fp):
         # updated self.added/removed, which are used by getfromtoline()
         self.added, self.removed = self.countchanges()
         fp.write(self.getfromtoline())
 
         hunklinelist = []
         # add the following to the list: (1) all applied lines, and
         # (2) all unapplied removal lines (convert these to context lines)
         for changedline in self.changedlines:
             changedlinestr = changedline.prettystr()
             if changedline.applied:
                 hunklinelist.append(changedlinestr)
             elif changedlinestr[0] == "-":
                 hunklinelist.append(" " + changedlinestr[1:])
 
         fp.write(''.join(self.before + hunklinelist + self.after))
 
     pretty = write
 
     def prettystr(self):
         x = stringio()
         self.pretty(x)
         return x.getvalue()
 
     def __getattr__(self, name):
         return getattr(self._hunk, name)
 
     def __repr__(self):
         return '<hunk %r@%d>' % (self.filename(), self.fromline)
 
 def filterpatch(ui, chunks, chunkselector, operation=None):
     """interactively filter patch chunks into applied-only chunks"""
 
     if operation is None:
         operation = _('confirm')
     chunks = list(chunks)
     # convert chunks list into structure suitable for displaying/modifying
     # with curses.  create a list of headers only.
     headers = [c for c in chunks if isinstance(c, patchmod.header)]
 
     # if there are no changed files
     if len(headers) == 0:
         return [], {}
     uiheaders = [uiheader(h) for h in headers]
     # let user choose headers/hunks/lines, and mark their applied flags
     # accordingly
     ret = chunkselector(ui, uiheaders)
     appliedhunklist = []
     for hdr in uiheaders:
         if (hdr.applied and
             (hdr.special() or len([h for h in hdr.hunks if h.applied]) > 0)):
             appliedhunklist.append(hdr)
             fixoffset = 0
             for hnk in hdr.hunks:
                 if hnk.applied:
                     appliedhunklist.append(hnk)
                     # adjust the 'to'-line offset of the hunk to be correct
                     # after de-activating some of the other hunks for this file
                     if fixoffset:
                         #hnk = copy.copy(hnk) # necessary??
                         hnk.toline += fixoffset
                 else:
                     fixoffset += hnk.removed - hnk.added
 
     return (appliedhunklist, ret)
 
 def gethw():
     """
     magically get the current height and width of the window (without initscr)
 
     this is a rip-off of a rip-off - taken from the bpython code.  it is
     useful / necessary because otherwise curses.initscr() must be called,
     which can leave the terminal in a nasty state after exiting.
     """
     h, w = struct.unpack(
         "hhhh", fcntl.ioctl(_origstdout, termios.TIOCGWINSZ, "\000"*8))[0:2]
     return h, w
 
 def chunkselector(ui, headerlist):
     """
     curses interface to get selection of chunks, and mark the applied flags
     of the chosen chunks.
     """
     ui.write(_('starting interactive selection\n'))
     chunkselector = curseschunkselector(headerlist, ui)
     f = signal.getsignal(signal.SIGTSTP)
     curses.wrapper(chunkselector.main)
     if chunkselector.initerr is not None:
         raise error.Abort(chunkselector.initerr)
     # ncurses does not restore signal handler for SIGTSTP
     signal.signal(signal.SIGTSTP, f)
     return chunkselector.opts
 
 def testdecorator(testfn, f):
     def u(*args, **kwargs):
         return f(testfn, *args, **kwargs)
     return u
 
 def testchunkselector(testfn, ui, headerlist):
     """
     test interface to get selection of chunks, and mark the applied flags
     of the chosen chunks.
     """
     chunkselector = curseschunkselector(headerlist, ui)
     if testfn and os.path.exists(testfn):
         testf = open(testfn)
         testcommands = map(lambda x: x.rstrip('\n'), testf.readlines())
         testf.close()
         while True:
             if chunkselector.handlekeypressed(testcommands.pop(0), test=True):
                 break
     return chunkselector.opts
 
 class curseschunkselector(object):
     def __init__(self, headerlist, ui):
         # put the headers into a patch object
         self.headerlist = patch(headerlist)
 
         self.ui = ui
         self.opts = {}
 
         self.errorstr = None
         # list of all chunks
         self.chunklist = []
         for h in headerlist:
             self.chunklist.append(h)
             self.chunklist.extend(h.hunks)
 
         # dictionary mapping (fgcolor, bgcolor) pairs to the
         # corresponding curses color-pair value.
         self.colorpairs = {}
         # maps custom nicknames of color-pairs to curses color-pair values
         self.colorpairnames = {}
 
         # the currently selected header, hunk, or hunk-line
         self.currentselecteditem = self.headerlist[0]
 
         # updated when printing out patch-display -- the 'lines' here are the
         # line positions *in the pad*, not on the screen.
         self.selecteditemstartline = 0
         self.selecteditemendline = None
 
         # define indentation levels
         self.headerindentnumchars = 0
         self.hunkindentnumchars = 3
         self.hunklineindentnumchars = 6
 
         # the first line of the pad to print to the screen
         self.firstlineofpadtoprint = 0
 
         # keeps track of the number of lines in the pad
         self.numpadlines = None
 
         self.numstatuslines = 2
 
         # keep a running count of the number of lines printed to the pad
         # (used for determining when the selected item begins/ends)
         self.linesprintedtopadsofar = 0
 
         # the first line of the pad which is visible on the screen
         self.firstlineofpadtoprint = 0
 
         # stores optional text for a commit comment provided by the user
         self.commenttext = ""
 
         # if the last 'toggle all' command caused all changes to be applied
         self.waslasttoggleallapplied = True
 
     def uparrowevent(self):
         """
         try to select the previous item to the current item that has the
         most-indented level.  for example, if a hunk is selected, try to select
         the last hunkline of the hunk prior to the selected hunk.  or, if
         the first hunkline of a hunk is currently selected, then select the
         hunk itself.
         """
         currentitem = self.currentselecteditem
 
-        nextitem = currentitem.previtem(constrainlevel=False)
+        nextitem = currentitem.previtem()
 
         if nextitem is None:
             # if no parent item (i.e. currentitem is the first header), then
             # no change...
             nextitem = currentitem
 
         self.currentselecteditem = nextitem
 
     def uparrowshiftevent(self):
         """
         select (if possible) the previous item on the same level as the
         currently selected item.  otherwise, select (if possible) the
         parent-item of the currently selected item.
         """
         currentitem = self.currentselecteditem
-        nextitem = currentitem.previtem()
-        # if there's no previous item on this level, try choosing the parent
+        nextitem = currentitem.prevsibling()
+        # if there's no previous sibling, try choosing the parent
         if nextitem is None:
             nextitem = currentitem.parentitem()
         if nextitem is None:
             # if no parent item (i.e. currentitem is the first header), then
             # no change...
             nextitem = currentitem
 
         self.currentselecteditem = nextitem
 
     def downarrowevent(self):
         """
         try to select the next item to the current item that has the
         most-indented level.  for example, if a hunk is selected, select
         the first hunkline of the selected hunk.  or, if the last hunkline of
         a hunk is currently selected, then select the next hunk, if one exists,
         or if not, the next header if one exists.
         """
         #self.startprintline += 1 #debug
         currentitem = self.currentselecteditem
 
-        nextitem = currentitem.nextitem(constrainlevel=False)
+        nextitem = currentitem.nextitem()
         # if there's no next item, keep the selection as-is
         if nextitem is None:
             nextitem = currentitem
 
         self.currentselecteditem = nextitem
 
     def downarrowshiftevent(self):
         """
         select (if possible) the next item on the same level as the currently
         selected item.  otherwise, select (if possible) the next item on the
         same level as the parent item of the currently selected item.
         """
         currentitem = self.currentselecteditem
-        nextitem = currentitem.nextitem()
-        # if there's no next item on this level, try choosing the parent's
-        # nextitem.
+        nextitem = currentitem.nextsibling()
+        # if there's no next sibling, try choosing the parent's nextsibling
         if nextitem is None:
             try:
-                nextitem = currentitem.parentitem().nextitem()
+                nextitem = currentitem.parentitem().nextsibling()
             except AttributeError:
-                # parentitem returned None, so nextitem() can't be called
+                # parentitem returned None, so nextsibling() can't be called
                 nextitem = None
         if nextitem is None:
-            # if no next item on parent-level, then no change...
+            # if parent has no next sibling, then no change...
             nextitem = currentitem
 
         self.currentselecteditem = nextitem
 
     def rightarrowevent(self):
         """
         select (if possible) the first of this item's child-items.
         """
         currentitem = self.currentselecteditem
         nextitem = currentitem.firstchild()
 
         # turn off folding if we want to show a child-item
         if currentitem.folded:
             self.togglefolded(currentitem)
 
         if nextitem is None:
             # if no next item on parent-level, then no change...
             nextitem = currentitem
 
         self.currentselecteditem = nextitem
 
     def leftarrowevent(self):
         """
         if the current item can be folded (i.e. it is an unfolded header or
         hunk), then fold it.  otherwise try select (if possible) the parent
         of this item.
         """
         currentitem = self.currentselecteditem
 
         # try to fold the item
         if not isinstance(currentitem, uihunkline):
             if not currentitem.folded:
                 self.togglefolded(item=currentitem)
                 return
 
         # if it can't be folded, try to select the parent item
         nextitem = currentitem.parentitem()
 
         if nextitem is None:
             # if no item on parent-level, then no change...
             nextitem = currentitem
             if not nextitem.folded:
                 self.togglefolded(item=nextitem)
 
         self.currentselecteditem = nextitem
 
     def leftarrowshiftevent(self):
         """
         select the header of the current item (or fold current item if the
         current item is already a header).
         """
         currentitem = self.currentselecteditem
 
         if isinstance(currentitem, uiheader):
             if not currentitem.folded:
                 self.togglefolded(item=currentitem)
                 return
 
         # select the parent item recursively until we're at a header
         while True:
             nextitem = currentitem.parentitem()
             if nextitem is None:
                 break
             else:
                 currentitem = nextitem
 
         self.currentselecteditem = currentitem
 
     def updatescroll(self):
         "scroll the screen to fully show the currently-selected"
         selstart = self.selecteditemstartline
         selend = self.selecteditemendline
         #selnumlines = selend - selstart
         padstart = self.firstlineofpadtoprint
         padend = padstart + self.yscreensize - self.numstatuslines - 1
         # 'buffered' pad start/end values which scroll with a certain
         # top/bottom context margin
         padstartbuffered = padstart + 3
         padendbuffered = padend - 3
 
         if selend > padendbuffered:
             self.scrolllines(selend - padendbuffered)
         elif selstart < padstartbuffered:
             # negative values scroll in pgup direction
             self.scrolllines(selstart - padstartbuffered)
 
     def scrolllines(self, numlines):
         "scroll the screen up (down) by numlines when numlines >0 (<0)."
         self.firstlineofpadtoprint += numlines
         if self.firstlineofpadtoprint < 0:
             self.firstlineofpadtoprint = 0
         if self.firstlineofpadtoprint > self.numpadlines - 1:
             self.firstlineofpadtoprint = self.numpadlines - 1
 
     def toggleapply(self, item=None):
         """
         toggle the applied flag of the specified item.  if no item is specified,
         toggle the flag of the currently selected item.
         """
         if item is None:
             item = self.currentselecteditem
 
         item.applied = not item.applied
 
         if isinstance(item, uiheader):
             item.partial = False
             if item.applied:
                 # apply all its hunks
                 for hnk in item.hunks:
                     hnk.applied = True
                     # apply all their hunklines
                     for hunkline in hnk.changedlines:
                         hunkline.applied = True
             else:
                 # un-apply all its hunks
                 for hnk in item.hunks:
                     hnk.applied = False
                     hnk.partial = False
                     # un-apply all their hunklines
                     for hunkline in hnk.changedlines:
                         hunkline.applied = False
         elif isinstance(item, uihunk):
             item.partial = False
             # apply all it's hunklines
             for hunkline in item.changedlines:
                 hunkline.applied = item.applied
 
             siblingappliedstatus = [hnk.applied for hnk in item.header.hunks]
             allsiblingsapplied = not (False in siblingappliedstatus)
             nosiblingsapplied = not (True in siblingappliedstatus)
 
             siblingspartialstatus = [hnk.partial for hnk in item.header.hunks]
             somesiblingspartial = (True in siblingspartialstatus)
 
             #cases where applied or partial should be removed from header
 
             # if no 'sibling' hunks are applied (including this hunk)
             if nosiblingsapplied:
                 if not item.header.special():
                     item.header.applied = False
                     item.header.partial = False
             else: # some/all parent siblings are applied
                 item.header.applied = True
                 item.header.partial = (somesiblingspartial or
                                         not allsiblingsapplied)
 
         elif isinstance(item, uihunkline):
             siblingappliedstatus = [ln.applied for ln in item.hunk.changedlines]
             allsiblingsapplied = not (False in siblingappliedstatus)
             nosiblingsapplied = not (True in siblingappliedstatus)
 
             # if no 'sibling' lines are applied
             if nosiblingsapplied:
                 item.hunk.applied = False
                 item.hunk.partial = False
             elif allsiblingsapplied:
                 item.hunk.applied = True
                 item.hunk.partial = False
             else: # some siblings applied
                 item.hunk.applied = True
                 item.hunk.partial = True
 
             parentsiblingsapplied = [hnk.applied for hnk
                                      in item.hunk.header.hunks]
             noparentsiblingsapplied = not (True in parentsiblingsapplied)
             allparentsiblingsapplied = not (False in parentsiblingsapplied)
 
             parentsiblingspartial = [hnk.partial for hnk
                                      in item.hunk.header.hunks]
             someparentsiblingspartial = (True in parentsiblingspartial)
 
             # if all parent hunks are not applied, un-apply header
             if noparentsiblingsapplied:
                 if not item.hunk.header.special():
                     item.hunk.header.applied = False
                     item.hunk.header.partial = False
             # set the applied and partial status of the header if needed
             else: # some/all parent siblings are applied
                 item.hunk.header.applied = True
                 item.hunk.header.partial = (someparentsiblingspartial or
                                             not allparentsiblingsapplied)
 
     def toggleall(self):
         "toggle the applied flag of all items."
         if self.waslasttoggleallapplied: # then unapply them this time
             for item in self.headerlist:
                 if item.applied:
                     self.toggleapply(item)
         else:
             for item in self.headerlist:
                 if not item.applied:
                     self.toggleapply(item)
         self.waslasttoggleallapplied = not self.waslasttoggleallapplied
 
     def togglefolded(self, item=None, foldparent=False):
         "toggle folded flag of specified item (defaults to currently selected)"
         if item is None:
             item = self.currentselecteditem
         if foldparent or (isinstance(item, uiheader) and item.neverunfolded):
             if not isinstance(item, uiheader):
                 # we need to select the parent item in this case
                 self.currentselecteditem = item = item.parentitem()
             elif item.neverunfolded:
                 item.neverunfolded = False
 
             # also fold any foldable children of the parent/current item
             if isinstance(item, uiheader): # the original or 'new' item
                 for child in item.allchildren():
                     child.folded = not item.folded
 
         if isinstance(item, (uiheader, uihunk)):
             item.folded = not item.folded
 
     def alignstring(self, instr, window):
         """
         add whitespace to the end of a string in order to make it fill
         the screen in the x direction.  the current cursor position is
         taken into account when making this calculation.  the string can span
         multiple lines.
         """
         y, xstart = window.getyx()
         width = self.xscreensize
         # turn tabs into spaces
         instr = instr.expandtabs(4)
         strwidth = encoding.colwidth(instr)
         numspaces = (width - ((strwidth + xstart) % width) - 1)
         return instr + " " * numspaces + "\n"
 
     def printstring(self, window, text, fgcolor=None, bgcolor=None, pair=None,
         pairname=None, attrlist=None, towin=True, align=True, showwhtspc=False):
         """
         print the string, text, with the specified colors and attributes, to
         the specified curses window object.
 
         the foreground and background colors are of the form
         curses.color_xxxx, where xxxx is one of: [black, blue, cyan, green,
         magenta, red, white, yellow].  if pairname is provided, a color
         pair will be looked up in the self.colorpairnames dictionary.
 
         attrlist is a list containing text attributes in the form of
         curses.a_xxxx, where xxxx can be: [bold, dim, normal, standout,
         underline].
 
         if align == True, whitespace is added to the printed string such that
         the string stretches to the right border of the window.
 
         if showwhtspc == True, trailing whitespace of a string is highlighted.
         """
         # preprocess the text, converting tabs to spaces
         text = text.expandtabs(4)
         # strip \n, and convert control characters to ^[char] representation
         text = re.sub(r'[\x00-\x08\x0a-\x1f]',
                 lambda m:'^' + chr(ord(m.group()) + 64), text.strip('\n'))
 
         if pair is not None:
             colorpair = pair
         elif pairname is not None:
             colorpair = self.colorpairnames[pairname]
         else:
             if fgcolor is None:
                 fgcolor = -1
             if bgcolor is None:
                 bgcolor = -1
             if (fgcolor, bgcolor) in self.colorpairs:
                 colorpair = self.colorpairs[(fgcolor, bgcolor)]
             else:
                 colorpair = self.getcolorpair(fgcolor, bgcolor)
         # add attributes if possible
         if attrlist is None:
             attrlist = []
         if colorpair < 256:
             # then it is safe to apply all attributes
             for textattr in attrlist:
                 colorpair |= textattr
         else:
             # just apply a select few (safe?) attributes
             for textattr in (curses.A_UNDERLINE, curses.A_BOLD):
                 if textattr in attrlist:
                     colorpair |= textattr
 
         y, xstart = self.chunkpad.getyx()
         t = "" # variable for counting lines printed
         # if requested, show trailing whitespace
         if showwhtspc:
             origlen = len(text)
             text = text.rstrip(' \n') # tabs have already been expanded
             strippedlen = len(text)
             numtrailingspaces = origlen - strippedlen
 
         if towin:
             window.addstr(text, colorpair)
         t += text
 
         if showwhtspc:
                 wscolorpair = colorpair | curses.A_REVERSE
                 if towin:
                     for i in range(numtrailingspaces):
                         window.addch(curses.ACS_CKBOARD, wscolorpair)
                 t += " " * numtrailingspaces
 
         if align:
             if towin:
                 extrawhitespace = self.alignstring("", window)
                 window.addstr(extrawhitespace, colorpair)
             else:
                 # need to use t, since the x position hasn't incremented
                 extrawhitespace = self.alignstring(t, window)
             t += extrawhitespace
 
         # is reset to 0 at the beginning of printitem()
 
         linesprinted = (xstart + len(t)) / self.xscreensize
         self.linesprintedtopadsofar += linesprinted
         return t
 
     def updatescreen(self):
         self.statuswin.erase()
         self.chunkpad.erase()
 
         printstring = self.printstring
 
         # print out the status lines at the top
         try:
             if self.errorstr is not None:
                 printstring(self.statuswin, self.errorstr, pairname='legend')
                 printstring(self.statuswin, 'Press any key to continue',
                             pairname='legend')
                 self.statuswin.refresh()
                 return
             line1 = ("SELECT CHUNKS: (j/k/up/dn/pgup/pgdn) move cursor; "
                    "(space/A) toggle hunk/all; (e)dit hunk;")
             line2 = (" (f)old/unfold; (c)onfirm applied; (q)uit; (?) help "
                    "| [X]=hunk applied **=folded, toggle [a]mend mode")
 
             printstring(self.statuswin,
                         util.ellipsis(line1, self.xscreensize - 1),
                         pairname="legend")
             printstring(self.statuswin,
                         util.ellipsis(line2, self.xscreensize - 1),
                         pairname="legend")
         except curses.error:
             pass
 
         # print out the patch in the remaining part of the window
         try:
             self.printitem()
             self.updatescroll()
             self.chunkpad.refresh(self.firstlineofpadtoprint, 0,
                                   self.numstatuslines, 0,
                                   self.yscreensize + 1 - self.numstatuslines,
                                   self.xscreensize)
         except curses.error:
             pass
 
         # refresh([pminrow, pmincol, sminrow, smincol, smaxrow, smaxcol])
         self.statuswin.refresh()
 
     def getstatusprefixstring(self, item):
         """
         create a string to prefix a line with which indicates whether 'item'
         is applied and/or folded.
         """
 
         # create checkbox string
         if item.applied:
             if not isinstance(item, uihunkline) and item.partial:
                 checkbox = "[~]"
             else:
                 checkbox = "[x]"
         else:
             checkbox = "[ ]"
 
         try:
             if item.folded:
                 checkbox += "**"
                 if isinstance(item, uiheader):
                     # one of "m", "a", or "d" (modified, added, deleted)
                     filestatus = item.changetype
 
                     checkbox += filestatus + " "
             else:
                 checkbox += "  "
                 if isinstance(item, uiheader):
                     # add two more spaces for headers
                     checkbox += "  "
         except AttributeError: # not foldable
             checkbox += "  "
 
         return checkbox
 
     def printheader(self, header, selected=False, towin=True,
                     ignorefolding=False):
         """
         print the header to the pad.  if countlines is True, don't print
         anything, but just count the number of lines which would be printed.
         """
 
         outstr = ""
         text = header.prettystr()
         chunkindex = self.chunklist.index(header)
 
         if chunkindex != 0 and not header.folded:
             # add separating line before headers
             outstr += self.printstring(self.chunkpad, '_' * self.xscreensize,
                                        towin=towin, align=False)
         # select color-pair based on if the header is selected
         colorpair = self.getcolorpair(name=selected and "selected" or "normal",
                                       attrlist=[curses.A_BOLD])
 
         # print out each line of the chunk, expanding it to screen width
 
         # number of characters to indent lines on this level by
         indentnumchars = 0
         checkbox = self.getstatusprefixstring(header)
         if not header.folded or ignorefolding:
             textlist = text.split("\n")
             linestr = checkbox + textlist[0]
         else:
             linestr = checkbox + header.filename()
         outstr += self.printstring(self.chunkpad, linestr, pair=colorpair,
                                    towin=towin)
         if not header.folded or ignorefolding:
             if len(textlist) > 1:
                 for line in textlist[1:]:
                     linestr = " "*(indentnumchars + len(checkbox)) + line
                     outstr += self.printstring(self.chunkpad, linestr,
                                                pair=colorpair, towin=towin)
 
         return outstr
 
     def printhunklinesbefore(self, hunk, selected=False, towin=True,
                              ignorefolding=False):
         "includes start/end line indicator"
         outstr = ""
         # where hunk is in list of siblings
         hunkindex = hunk.header.hunks.index(hunk)
 
         if hunkindex != 0:
             # add separating line before headers
             outstr += self.printstring(self.chunkpad, ' '*self.xscreensize,
                                        towin=towin, align=False)
 
         colorpair = self.getcolorpair(name=selected and "selected" or "normal",
                                       attrlist=[curses.A_BOLD])
 
         # print out from-to line with checkbox
         checkbox = self.getstatusprefixstring(hunk)
 
         lineprefix = " "*self.hunkindentnumchars + checkbox
         frtoline = "   " + hunk.getfromtoline().strip("\n")
 
         outstr += self.printstring(self.chunkpad, lineprefix, towin=towin,
                                    align=False) # add uncolored checkbox/indent
         outstr += self.printstring(self.chunkpad, frtoline, pair=colorpair,
                                    towin=towin)
 
         if hunk.folded and not ignorefolding:
             # skip remainder of output
             return outstr
 
         # print out lines of the chunk preceeding changed-lines
         for line in hunk.before:
             linestr = " "*(self.hunklineindentnumchars + len(checkbox)) + line
             outstr += self.printstring(self.chunkpad, linestr, towin=towin)
 
         return outstr
 
     def printhunklinesafter(self, hunk, towin=True, ignorefolding=False):
         outstr = ""
         if hunk.folded and not ignorefolding:
             return outstr
 
         # a bit superfluous, but to avoid hard-coding indent amount
         checkbox = self.getstatusprefixstring(hunk)
         for line in hunk.after:
             linestr = " "*(self.hunklineindentnumchars + len(checkbox)) + line
             outstr += self.printstring(self.chunkpad, linestr, towin=towin)
 
         return outstr
 
     def printhunkchangedline(self, hunkline, selected=False, towin=True):
         outstr = ""
         checkbox = self.getstatusprefixstring(hunkline)
 
         linestr = hunkline.prettystr().strip("\n")
 
         # select color-pair based on whether line is an addition/removal
         if selected:
             colorpair = self.getcolorpair(name="selected")
         elif linestr.startswith("+"):
             colorpair = self.getcolorpair(name="addition")
         elif linestr.startswith("-"):
             colorpair = self.getcolorpair(name="deletion")
         elif linestr.startswith("\\"):
             colorpair = self.getcolorpair(name="normal")
 
         lineprefix = " "*self.hunklineindentnumchars + checkbox
         outstr += self.printstring(self.chunkpad, lineprefix, towin=towin,
                                    align=False) # add uncolored checkbox/indent
         outstr += self.printstring(self.chunkpad, linestr, pair=colorpair,
                                    towin=towin, showwhtspc=True)
         return outstr
 
     def printitem(self, item=None, ignorefolding=False, recursechildren=True,
                   towin=True):
         """
         use __printitem() to print the the specified item.applied.
         if item is not specified, then print the entire patch.
         (hiding folded elements, etc. -- see __printitem() docstring)
         """
 
         if item is None:
             item = self.headerlist
         if recursechildren:
             self.linesprintedtopadsofar = 0
 
         outstr = []
         self.__printitem(item, ignorefolding, recursechildren, outstr,
                                   towin=towin)
         return ''.join(outstr)
 
     def outofdisplayedarea(self):
         y, _ = self.chunkpad.getyx() # cursor location
         # * 2 here works but an optimization would be the max number of
         # consecutive non selectable lines
         # i.e the max number of context line for any hunk in the patch
         miny = min(0, self.firstlineofpadtoprint - self.yscreensize)
         maxy = self.firstlineofpadtoprint + self.yscreensize * 2
         return y < miny or y > maxy
 
     def handleselection(self, item, recursechildren):
         selected = (item is self.currentselecteditem)
         if selected and recursechildren:
             # assumes line numbering starting from line 0
             self.selecteditemstartline = self.linesprintedtopadsofar
             selecteditemlines = self.getnumlinesdisplayed(item,
                                                           recursechildren=False)
             self.selecteditemendline = (self.selecteditemstartline +
                                         selecteditemlines - 1)
         return selected
 
     def __printitem(self, item, ignorefolding, recursechildren, outstr,
                     towin=True):
         """
         recursive method for printing out patch/header/hunk/hunk-line data to
         screen.  also returns a string with all of the content of the displayed
         patch (not including coloring, etc.).
 
         if ignorefolding is True, then folded items are printed out.
 
         if recursechildren is False, then only print the item without its
         child items.
         """
 
         if towin and self.outofdisplayedarea():
             return
 
         selected = self.handleselection(item, recursechildren)
 
         # patch object is a list of headers
         if isinstance(item, patch):
             if recursechildren:
                 for hdr in item:
                     self.__printitem(hdr, ignorefolding,
                             recursechildren, outstr, towin)
         # todo: eliminate all isinstance() calls
         if isinstance(item, uiheader):
             outstr.append(self.printheader(item, selected, towin=towin,
                                        ignorefolding=ignorefolding))
             if recursechildren:
                 for hnk in item.hunks:
                     self.__printitem(hnk, ignorefolding,
                             recursechildren, outstr, towin)
         elif (isinstance(item, uihunk) and
               ((not item.header.folded) or ignorefolding)):
             # print the hunk data which comes before the changed-lines
             outstr.append(self.printhunklinesbefore(item, selected, towin=towin,
                                                 ignorefolding=ignorefolding))
             if recursechildren:
                 for l in item.changedlines:
                     self.__printitem(l, ignorefolding,
                             recursechildren, outstr, towin)
                 outstr.append(self.printhunklinesafter(item, towin=towin,
                                                 ignorefolding=ignorefolding))
         elif (isinstance(item, uihunkline) and
               ((not item.hunk.folded) or ignorefolding)):
             outstr.append(self.printhunkchangedline(item, selected,
                 towin=towin))
 
         return outstr
 
     def getnumlinesdisplayed(self, item=None, ignorefolding=False,
                              recursechildren=True):
         """
         return the number of lines which would be displayed if the item were
         to be printed to the display.  the item will not be printed to the
         display (pad).
         if no item is given, assume the entire patch.
         if ignorefolding is True, folded items will be unfolded when counting
         the number of lines.
         """
 
         # temporarily disable printing to windows by printstring
         patchdisplaystring = self.printitem(item, ignorefolding,
                                             recursechildren, towin=False)
         numlines = len(patchdisplaystring) / self.xscreensize
         return numlines
 
     def sigwinchhandler(self, n, frame):
         "handle window resizing"
         try:
             curses.endwin()
             self.yscreensize, self.xscreensize = gethw()
             self.statuswin.resize(self.numstatuslines, self.xscreensize)
             self.numpadlines = self.getnumlinesdisplayed(ignorefolding=True) + 1
             self.chunkpad = curses.newpad(self.numpadlines, self.xscreensize)
             # todo: try to resize commit message window if possible
         except curses.error:
             pass
 
     def getcolorpair(self, fgcolor=None, bgcolor=None, name=None,
                      attrlist=None):
         """
         get a curses color pair, adding it to self.colorpairs if it is not
         already defined.  an optional string, name, can be passed as a shortcut
         for referring to the color-pair.  by default, if no arguments are
         specified, the white foreground / black background color-pair is
         returned.
 
         it is expected that this function will be used exclusively for
         initializing color pairs, and not curses.init_pair().
 
         attrlist is used to 'flavor' the returned color-pair.  this information
         is not stored in self.colorpairs.  it contains attribute values like
         curses.A_BOLD.
         """
 
         if (name is not None) and name in self.colorpairnames:
             # then get the associated color pair and return it
             colorpair = self.colorpairnames[name]
         else:
             if fgcolor is None:
                 fgcolor = -1
             if bgcolor is None:
                 bgcolor = -1
             if (fgcolor, bgcolor) in self.colorpairs:
                 colorpair = self.colorpairs[(fgcolor, bgcolor)]
             else:
                 pairindex = len(self.colorpairs) + 1
                 curses.init_pair(pairindex, fgcolor, bgcolor)
                 colorpair = self.colorpairs[(fgcolor, bgcolor)] = (
                     curses.color_pair(pairindex))
                 if name is not None:
                     self.colorpairnames[name] = curses.color_pair(pairindex)
 
         # add attributes if possible
         if attrlist is None:
             attrlist = []
         if colorpair < 256:
             # then it is safe to apply all attributes
             for textattr in attrlist:
                 colorpair |= textattr
         else:
             # just apply a select few (safe?) attributes
             for textattrib in (curses.A_UNDERLINE, curses.A_BOLD):
                 if textattrib in attrlist:
                     colorpair |= textattrib
         return colorpair
 
     def initcolorpair(self, *args, **kwargs):
         "same as getcolorpair."
         self.getcolorpair(*args, **kwargs)
 
     def helpwindow(self):
         "print a help window to the screen.  exit after any keypress."
         helptext = """            [press any key to return to the patch-display]
 
 crecord allows you to interactively choose among the changes you have made,
 and confirm only those changes you select for further processing by the command
 you are running (commit/shelve/revert), after confirming the selected
 changes, the unselected changes are still present in your working copy, so you
 can use crecord multiple times to split large changes into smaller changesets.
 the following are valid keystrokes:
 
                 [space] : (un-)select item ([~]/[x] = partly/fully applied)
                       A : (un-)select all items
     up/down-arrow [k/j] : go to previous/next unfolded item
         pgup/pgdn [K/J] : go to previous/next item of same type
  right/left-arrow [l/h] : go to child item / parent item
  shift-left-arrow   [H] : go to parent header / fold selected header
                       f : fold / unfold item, hiding/revealing its children
                       F : fold / unfold parent item and all of its ancestors
                       m : edit / resume editing the commit message
                       e : edit the currently selected hunk
                       a : toggle amend mode, only with commit -i
                       c : confirm selected changes
                       r : review/edit and confirm selected changes
                       q : quit without confirming (no changes will be made)
                       ? : help (what you're currently reading)"""
 
         helpwin = curses.newwin(self.yscreensize, 0, 0, 0)
         helplines = helptext.split("\n")
         helplines = helplines + [" "]*(
             self.yscreensize - self.numstatuslines - len(helplines) - 1)
         try:
             for line in helplines:
                 self.printstring(helpwin, line, pairname="legend")
         except curses.error:
             pass
         helpwin.refresh()
         try:
             helpwin.getkey()
         except curses.error:
             pass
 
     def confirmationwindow(self, windowtext):
         "display an informational window, then wait for and return a keypress."
 
         confirmwin = curses.newwin(self.yscreensize, 0, 0, 0)
         try:
             lines = windowtext.split("\n")
             for line in lines:
                 self.printstring(confirmwin, line, pairname="selected")
         except curses.error:
             pass
         self.stdscr.refresh()
         confirmwin.refresh()
         try:
             response = chr(self.stdscr.getch())
         except ValueError:
             response = None
 
         return response
 
     def reviewcommit(self):
         """ask for 'y' to be pressed to confirm selected. return True if
         confirmed."""
         confirmtext = (
 """if you answer yes to the following, the your currently chosen patch chunks
 will be loaded into an editor.  you may modify the patch from the editor, and
 save the changes if you wish to change the patch.  otherwise, you can just
 close the editor without saving to accept the current patch as-is.
 
 note: don't add/remove lines unless you also modify the range information.
       failing to follow this rule will result in the commit aborting.
 
 are you sure you want to review/edit and confirm the selected changes [yn]?
 """)
         response = self.confirmationwindow(confirmtext)
         if response is None:
             response = "n"
         if response.lower().startswith("y"):
             return True
         else:
             return False
 
     def toggleamend(self, opts, test):
         """Toggle the amend flag.
 
         When the amend flag is set, a commit will modify the most recently
         committed changeset, instead of creating a new changeset.  Otherwise, a
         new changeset will be created (the normal commit behavior).
         """
 
         try:
             ver = float(util.version()[:3])
         except ValueError:
             ver = 1
         if ver < 2.19:
             msg = ("The amend option is unavailable with hg versions < 2.2\n\n"
                    "Press any key to continue.")
         elif opts.get('amend') is None:
             opts['amend'] = True
             msg = ("Amend option is turned on -- commiting the currently "
                    "selected changes will not create a new changeset, but "
                    "instead update the most recently committed changeset.\n\n"
                    "Press any key to continue.")
         elif opts.get('amend') is True:
             opts['amend'] = None
             msg = ("Amend option is turned off -- commiting the currently "
                    "selected changes will create a new changeset.\n\n"
                    "Press any key to continue.")
         if not test:
             self.confirmationwindow(msg)
 
     def recenterdisplayedarea(self):
         """
         once we scrolled with pg up pg down we can be pointing outside of the
         display zone. we print the patch with towin=False to compute the
         location of the selected item even though it is outside of the displayed
         zone and then update the scroll.
         """
         self.printitem(towin=False)
         self.updatescroll()
 
     def toggleedit(self, item=None, test=False):
         """
         edit the currently selected chunk
         """
         def updateui(self):
             self.numpadlines = self.getnumlinesdisplayed(ignorefolding=True) + 1
             self.chunkpad = curses.newpad(self.numpadlines, self.xscreensize)
             self.updatescroll()
             self.stdscr.refresh()
             self.statuswin.refresh()
             self.stdscr.keypad(1)
 
         def editpatchwitheditor(self, chunk):
             if chunk is None:
                 self.ui.write(_('cannot edit patch for whole file'))
                 self.ui.write("\n")
                 return None
             if chunk.header.binary():
                 self.ui.write(_('cannot edit patch for binary file'))
                 self.ui.write("\n")
                 return None
 
             # write the initial patch
             patch = stringio()
             patch.write(diffhelptext + hunkhelptext)
             chunk.header.write(patch)
             chunk.write(patch)
 
             # start the editor and wait for it to complete
             try:
                 patch = self.ui.edit(patch.getvalue(), "",
                                      extra={"suffix": ".diff"})
             except error.Abort as exc:
                 self.errorstr = str(exc)
                 return None
 
             # remove comment lines
             patch = [line + '\n' for line in patch.splitlines()
                      if not line.startswith('#')]
             return patchmod.parsepatch(patch)
 
         if item is None:
             item = self.currentselecteditem
         if isinstance(item, uiheader):
             return
         if isinstance(item, uihunkline):
             item = item.parentitem()
         if not isinstance(item, uihunk):
             return
 
         # To go back to that hunk or its replacement at the end of the edit
         itemindex = item.parentitem().hunks.index(item)
 
         beforeadded, beforeremoved = item.added, item.removed
         newpatches = editpatchwitheditor(self, item)
         if newpatches is None:
             if not test:
                 updateui(self)
             return
         header = item.header
         editedhunkindex = header.hunks.index(item)
         hunksbefore = header.hunks[:editedhunkindex]
         hunksafter = header.hunks[editedhunkindex + 1:]
         newpatchheader = newpatches[0]
         newhunks = [uihunk(h, header) for h in newpatchheader.hunks]
         newadded = sum([h.added for h in newhunks])
         newremoved = sum([h.removed for h in newhunks])
         offset = (newadded - beforeadded) - (newremoved - beforeremoved)
 
         for h in hunksafter:
             h.toline += offset
         for h in newhunks:
             h.folded = False
         header.hunks = hunksbefore + newhunks + hunksafter
         if self.emptypatch():
             header.hunks = hunksbefore + [item] + hunksafter
         self.currentselecteditem = header
         if len(header.hunks) > itemindex:
             self.currentselecteditem = header.hunks[itemindex]
 
         if not test:
             updateui(self)
 
     def emptypatch(self):
         item = self.headerlist
         if not item:
             return True
         for header in item:
             if header.hunks:
                 return False
         return True
 
     def handlekeypressed(self, keypressed, test=False):
         """
         Perform actions based on pressed keys.
 
         Return true to exit the main loop.
         """
         if keypressed in ["k", "KEY_UP"]:
             self.uparrowevent()
         if keypressed in ["K", "KEY_PPAGE"]:
             self.uparrowshiftevent()
         elif keypressed in ["j", "KEY_DOWN"]:
             self.downarrowevent()
         elif keypressed in ["J", "KEY_NPAGE"]:
             self.downarrowshiftevent()
         elif keypressed in ["l", "KEY_RIGHT"]:
             self.rightarrowevent()
         elif keypressed in ["h", "KEY_LEFT"]:
             self.leftarrowevent()
         elif keypressed in ["H", "KEY_SLEFT"]:
             self.leftarrowshiftevent()
         elif keypressed in ["q"]:
             raise error.Abort(_('user quit'))
         elif keypressed in ['a']:
             self.toggleamend(self.opts, test)
         elif keypressed in ["c"]:
             return True
         elif test and keypressed in ['X']:
             return True
         elif keypressed in ["r"]:
             if self.reviewcommit():
                 self.opts['review'] = True
                 return True
         elif test and keypressed in ['R']:
             self.opts['review'] = True
             return True
         elif keypressed in [' '] or (test and keypressed in ["TOGGLE"]):
             self.toggleapply()
         elif keypressed in ['A']:
             self.toggleall()
         elif keypressed in ['e']:
             self.toggleedit(test=test)
         elif keypressed in ["f"]:
             self.togglefolded()
         elif keypressed in ["F"]:
             self.togglefolded(foldparent=True)
         elif keypressed in ["?"]:
             self.helpwindow()
             self.stdscr.clear()
             self.stdscr.refresh()
 
     def main(self, stdscr):
         """
         method to be wrapped by curses.wrapper() for selecting chunks.
         """
 
         signal.signal(signal.SIGWINCH, self.sigwinchhandler)
         self.stdscr = stdscr
         # error during initialization, cannot be printed in the curses
         # interface, it should be printed by the calling code
         self.initerr = None
         self.yscreensize, self.xscreensize = self.stdscr.getmaxyx()
 
         curses.start_color()
         curses.use_default_colors()
 
         # available colors: black, blue, cyan, green, magenta, white, yellow
         # init_pair(color_id, foreground_color, background_color)
         self.initcolorpair(None, None, name="normal")
         self.initcolorpair(curses.COLOR_WHITE, curses.COLOR_MAGENTA,
                            name="selected")
         self.initcolorpair(curses.COLOR_RED, None, name="deletion")
         self.initcolorpair(curses.COLOR_GREEN, None, name="addition")
         self.initcolorpair(curses.COLOR_WHITE, curses.COLOR_BLUE, name="legend")
         # newwin([height, width,] begin_y, begin_x)
         self.statuswin = curses.newwin(self.numstatuslines, 0, 0, 0)
         self.statuswin.keypad(1) # interpret arrow-key, etc. esc sequences
 
         # figure out how much space to allocate for the chunk-pad which is
         # used for displaying the patch
 
         # stupid hack to prevent getnumlinesdisplayed from failing
         self.chunkpad = curses.newpad(1, self.xscreensize)
 
         # add 1 so to account for last line text reaching end of line
         self.numpadlines = self.getnumlinesdisplayed(ignorefolding=True) + 1
 
         try:
             self.chunkpad = curses.newpad(self.numpadlines, self.xscreensize)
         except curses.error:
             self.initerr = _('this diff is too large to be displayed')
             return
         # initialize selecteitemendline (initial start-line is 0)
         self.selecteditemendline = self.getnumlinesdisplayed(
             self.currentselecteditem, recursechildren=False)
 
         while True:
             self.updatescreen()
             try:
                 keypressed = self.statuswin.getkey()
                 if self.errorstr is not None:
                     self.errorstr = None
                     continue
             except curses.error:
                 keypressed = "foobar"
             if self.handlekeypressed(keypressed):
                 break