[reportlab-users] probable bug in renderbase.StateTracker treatment of transforms

[Boris Borcic]

Hello,

In short, shouldn't renderbase.StateTracker.pop() read like :

     def pop(self) :
         del self._combined[-1]
         prevState = self._combined[-1]
         lastDelta = self._deltas.pop()
         reverseDelta = {}
         for key, curValue in lastDelta.items():
             if key == 'transform' :
                 if curValue != (1 0 0 1 0 0) :
                     reverseDelta[key] = inverse(curValue)
             elif curValue <> prevState[key] :
                 reverseDelta[key] = prevState[key]
         return reverseDelta

rather than the current :

     def pop(self):
         """steps back one, and returns a state dictionary with the
         deltas to reverse out of wherever you are.  Depending
         on your back end, you may not need the return value,
         since you can get the complete state afterwards with getState()"""

         del self._combined[-1]
         newState = self._combined[-1]
         lastDelta = self._deltas[-1]
         del  self._deltas[-1]
         #need to diff this against the last one in the state
         reverseDelta = {}
         #print 'pop()...'
         for key, curValue in lastDelta.items():
             prevValue = newState[key]
----------->if prevValue <> curValue:
----------->    if key == 'transform':
----------->        reverseDelta[key] = inverse(lastDelta['transform'])
                 else:  #just return to previous state
                     reverseDelta[key] = prevValue
         return reverseDelta

The 3 lines marked by arrows look inconsistent to me. If lastDelta['transform'] 
needs to be special-cased as it is there, this means that the condition of 
relevance for it, is not that prevValue<>curValue but rather that curValue isn't 
the identity transform.

Or am I missing something ?

TIA for comments,

Boris Borcic