def __init__(self,scr,title = "Choose a Buffer", buffers = []):
    max_y,max_x = scr.getmaxyx()
    dw = max_x - 4
    lw = dw - 4
    lx = dw//2 - lw//2
    self.buffer_list = dialog.ListBox("buffers",1,lx,2,12,lw,"Buffers",0,buffers)
    dialog.Dialog.__init__(self,scr,"BufferDialog",20,dw, [ dialog.Frame(title),
                                                          self.buffer_list,
                                      dialog.Button("Ok",2,2,16,"OK",dialog.Component.CMP_KEY_OK),
                                      dialog.Button("Cancel",3,9,16,"CANCEL",dialog.Component.CMP_KEY_CANCEL)])

def btab(self):
    if self.focus_list:
        self.push_history(self.focus_list[self.current][1])
        self.current -= 1
        if self.current < 0:
            self.current = len(self.focus_list)-1

def focus(self):
    self.focus_list = []
    for c in self.children:
        self.pop_history(c)
        if c.getorder() > 0:
            self.focus_list.append((c.getorder(),c))
    if not self.focus_list:
        self.current = 0
        return
    self.focus_list.sort(key=lambda x: x[0])
    self.current = 0

def getname(self):
    """ get the name of this component """
    return self.name

def getorder(self):
    """ get this component's tab order number """
    return self.order

def getparent(self):
    """ get this component's curses target window """
    return self.parent

def getvalue(self):
    value = {}
    for c in self.children:
        if c.getname():
            value[c.getname()] = c.getvalue()
    return value

def goto(self, component):
    """ move focus to this component """
    for i in range(0,len(self.focus_list)):
        if self.focus_list[i][1] == component:
            self.current = i
            return True
    return False

def handle(self, ch):
    if self.focus_list and ch != keytab.KEYTAB_MOUSE:
        ch = self.focus_list[self.current][1].handle(ch)
    cmd_id,ch = keymap.mapseq( keymap.keymap_dialog, ch)
    if extension_manager.is_extension(cmd_id):
        if not extension_manager.invoke_extension( cmd_id, self, ch ):
            return ch
    if cmd_id == cmd_names.CMD_DLGNEXT:
        self.tab()
    elif cmd_id == cmd_names.CMD_DLGPREV:
        self.btab()
    elif cmd_id == cmd_names.CMD_DLGUP:
        if self.focus_list:
            self.pop_history(self.focus_list[self.current][1])
        ch = Component.CMP_KEY_NOP
    elif cmd_id == cmd_names.CMD_DLGMOUSE:
        ret = self.handle_mouse()
        if ret >= 0:
            ch = ret
    elif cmd_id == cmd_names.CMD_DLGRESIZE:
        self.resize()
    return ch

def handle_mouse(self):
    if self.focus_list and self.win:
        try:
            mid, mx, my, mz, mtype = curses.getmouse()
            by,bx = self.win.getbegyx()
            oy = my - by
            ox = mx - bx
            for i in range(0,len(self.focus_list)):
                c = self.focus_list[i][1]
                ret = c.mouse_event(ox,oy,mtype)
                if ret >= 0:
                    self.current = i
                    return ret
            else:
                return -1
        except:
            return -1

def isempty(self):
    """ test if the component entry is empty """
    return False

def main(self,blocking = True,force=False,ch_in = None):
    curses.mousemask( curses.BUTTON1_PRESSED| curses.BUTTON1_RELEASED| curses.BUTTON1_CLICKED)
    self.win.nodelay(1)
    self.win.notimeout(0)
    self.win.timeout(0)
    old_cursor = curses.curs_set(1)
    while (1):
        if (not keymap.keypending(self.win)) or force:
            self.render()
        if not ch_in:
            ch = self.handle(keymap.get_keyseq(self.win,keymap.getch(self.win)))
        else:
            ch = self.handle(ch_in)
        if blocking:
            if ch == Component.CMP_KEY_CANCEL:
                curses.curs_set(old_cursor)
                return {}
            elif ch == Component.CMP_KEY_OK:
                curses.curs_set(old_cursor)
                return self.getvalue()
        else:
            if ch == Component.CMP_KEY_CANCEL:
                curses.curs_set(old_cursor)
                return (ch, {})
            else:
                curses.curs_set(old_cursor)
                return (ch, self.getvalue())

def mouse_event(self, ox, oy, mtype):
    """ handle mouse events return key value or -1 for not handled """
    return -1

def pop_history( self, child ):
    if not self.enable_history:
        return
    if not issubclass(child.__class__, Prompt):
        return
    if self.getname() and child.getname() and child.getorder() >= 0:
        key = (self.getname(), child.getname())
        if key in Dialog.history:
            hist = Dialog.history[key]
            self.hist_idx += 1
            if self.hist_idx > len(hist):
                self.hist_idx = 0
            child.setvalue(hist[-self.hist_idx])

def push_history( self, child ):
    if not self.enable_history:
        return
    if not issubclass(child.__class__, Prompt):
        return
    if self.getname() and child.getname() and child.getorder() >= 0 and not child.isempty():
        key = (self.getname(), child.getname())
        if key in Dialog.history:
            if Dialog.history[key][-1] != child.getvalue():
                Dialog.history[key].append(child.getvalue())
        else:
            Dialog.history[key] = [child.getvalue()]

def render(self):
    self.win.leaveok(1)
    for c in self.children:
        if not self.focus_list or self.focus_list[self.current][1] != c:
            c.render()
    self.win.leaveok(0)
    if self.focus_list:
        self.focus_list[self.current][1].focus()
        self.focus_list[self.current][1].render()
    self.win.refresh()

def resize(self):
    pass

def set_history( self, state ):
    self.enable_history = state

def setparent(self,parent):
    """ set the parent curses target window """
    self.parent = parent

def setpos(self, x, y ):
    """ set the position of this component """
    self.x = x
    self.y = y

def setsize(self, height, width ):
    """ set the width of this component """
    self.height = height
    self.width = width

def setvalue(self, value):
    for c in self.children:
        if c.getname() in value:
            c.setvalue(value[c.getname()])
            self.push_history(c)

def tab(self):
    if self.focus_list:
        self.push_history(self.focus_list[self.current][1])
        self.current += 1
        if self.current >= len(self.focus_list):
            self.current = 0