12 

    13 #-------------------------------------------------------------------------------

    14 #                         Undo Buffer for PythonCode

    15 #-------------------------------------------------------------------------------

    16 

    17 # Length of the buffer

    18 UNDO_BUFFER_LENGTH = 20

    19 

    20 """

    21 Class implementing a buffer of changes made on the current editing model

    22 """

    23 class UndoBuffer:

    24 

    25     # Constructor initialising buffer

    26     def __init__(self, currentstate, issaved = False):

    27         self.Buffer = []

    28         self.CurrentIndex = -1

    29         self.MinIndex = -1

    30         self.MaxIndex = -1

    31         # if current state is defined

    32         if currentstate:

    33             self.CurrentIndex = 0

    34             self.MinIndex = 0

    35             self.MaxIndex = 0

    36         # Initialising buffer with currentstate at the first place

    37         for i in xrange(UNDO_BUFFER_LENGTH):

    38             if i == 0:

    39                 self.Buffer.append(currentstate)

    40             else:

    41                 self.Buffer.append(None)

    42         # Initialising index of state saved

    43         if issaved:

    44             self.LastSave = 0

    45         else:

    46             self.LastSave = -1

    47     

    48     # Add a new state in buffer

    49     def Buffering(self, currentstate):

    50         self.CurrentIndex = (self.CurrentIndex + 1) % UNDO_BUFFER_LENGTH

    51         self.Buffer[self.CurrentIndex] = currentstate

    52         # Actualising buffer limits

    53         self.MaxIndex = self.CurrentIndex

    54         if self.MinIndex == self.CurrentIndex:

    55             # If the removed state was the state saved, there is no state saved in the buffer

    56             if self.LastSave == self.MinIndex:

    57                 self.LastSave = -1

    58             self.MinIndex = (self.MinIndex + 1) % UNDO_BUFFER_LENGTH

    59         self.MinIndex = max(self.MinIndex, 0)

    60     

    61     # Return current state of buffer

    62     def Current(self):

    63         return self.Buffer[self.CurrentIndex]

    64     

    65     # Change current state to previous in buffer and return new current state

    66     def Previous(self):

    67         if self.CurrentIndex != self.MinIndex:

    68             self.CurrentIndex = (self.CurrentIndex - 1) % UNDO_BUFFER_LENGTH

    69             return self.Buffer[self.CurrentIndex]

    70         return None

    71     

    72     # Change current state to next in buffer and return new current state

    73     def Next(self):

    74         if self.CurrentIndex != self.MaxIndex:

    75             self.CurrentIndex = (self.CurrentIndex + 1) % UNDO_BUFFER_LENGTH

    76             return self.Buffer[self.CurrentIndex]

    77         return None

    78     

    79     # Return True if current state is the first in buffer

    80     def IsFirst(self):

    81         return self.CurrentIndex == self.MinIndex

    82     

    83     # Return True if current state is the last in buffer

    84     def IsLast(self):

    85         return self.CurrentIndex == self.MaxIndex

    86 

    87     # Note that current state is saved

    88     def CurrentSaved(self):

    89         self.LastSave = self.CurrentIndex

    90         

    91     # Return True if current state is saved

    92     def IsCurrentSaved(self):

    93         return self.LastSave == self.CurrentIndex