###############################################################################

#   $Log $

#   

#   

"""

Superclass for renderers to factor out common functionality and default implementations.

"""

__version__=''' $Id $ '''

from reportlab.graphics.shapes import *

def inverse(A):

    "For A affine 2D represented as 6vec return 6vec version of A**(-1)"

    # I checked this RGB

    det = float(A[0]*A[3] - A[2]*A[1])

    R = [A[3]/det, -A[1]/det, -A[2]/det, A[0]/det]

    return tuple(R+[-R[0]*A[4]-R[2]*A[5],-R[1]*A[4]-R[3]*A[5]])

def mmult(A, B):

    "A postmultiplied by B"

    # I checked this RGB

    # [a0 a2 a4]    [b0 b2 b4]

    # [a1 a3 a5] *  [b1 b3 b5]

    # [      1 ]    [      1 ]

    #

    return (A[0]*B[0] + A[2]*B[1],

            A[1]*B[0] + A[3]*B[1],

            A[0]*B[2] + A[2]*B[3],

            A[1]*B[2] + A[3]*B[3],

            A[0]*B[4] + A[2]*B[5] + A[4],

            A[1]*B[4] + A[3]*B[5] + A[5])

def getStateDelta(shape):

    """Used to compute when we need to change the graphics state.

    For example, if we have two adjacent red shapes we don't need

    to set the pen color to red in between. Returns the effect

    the given shape would have on the graphics state"""

    delta = {}

    for (prop, value) in shape.getProperties().items():

        if STATE_DEFAULTS.has_key(prop):

            delta[prop] = value

    return delta

class StateTracker:

    """Keeps a stack of transforms and state

    properties.  It can contain any properties you

    want, but the keys 'transform' and 'ctm' have

    special meanings.  The getCTM()

    method returns the current transformation

    matrix at any point, without needing to

    invert matrixes when you pop."""

    def __init__(self, defaults=None):

        # one stack to keep track of what changes...

        self.__deltas = []

        # and another to keep track of cumulative effects.  Last one in

        # list is the current graphics state.  We put one in to simplify

        # loops below.

        self.__combined = []

        if defaults is None:

            defaults = STATE_DEFAULTS.copy()

        self.__combined.append(defaults)

    def push(self,delta):

        """Take a new state dictionary of changes and push it onto

        the stack.  After doing this, the combined state is accessible

        through getState()"""

        newstate = self.__combined[-1].copy()

        for (key, value) in delta.items():

            if key == 'transform':  #do cumulative matrix

                newstate['transform'] = delta['transform']

                newstate['ctm'] = mmult(self.__combined[-1]['transform'], delta['transform'])

            else:  #just overwrite it

                newstate[key] = value

        self.__combined.append(newstate)

        self.__deltas.append(delta)

    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 endm, 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 = {}

        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

    def getState(self):

        "returns the complete graphics state at this point"

        return self.__combined[-1]

    def getCTM(self):

        "returns the current transformation matrix at this point"""

        return self.__combined[-1]['ctm']

def testStateTracker():

    print 'Testing state tracker'

    defaults = {'fillColor':None, 'strokeColor':None,'fontName':None, 'transform':[1,0,0,1,0,0]}

    deltas = [

        {'fillColor':'red'},

        {'fillColor':'green', 'strokeColor':'blue','fontName':'Times-Roman'},

        {'transform':[0.5,0,0,0.5,0,0]},

        {'transform':[0.5,0,0,0.5,2,3]},

        {'strokeColor':'red'}

        ]

    st = StateTracker(defaults)

    print 'initial:', st.getState()

    print

    for delta in deltas:

        print 'pushing:', delta

        st.push(delta)

        print 'state:  ',st.getState(),'\n'

    for delta in deltas:

        print 'popping:',st.pop()

        print 'state:  ',st.getState(),'\n'

class Renderer:

    """Virtual superclass for Pingo renderers."""

    def __init__(self):

        self._tracker = StateTracker()

    def undefined(self, operation):

        raise ValueError, "%s operation not defined at superclass class=%s" %(operation, self.__class__)

    def draw(self, drawing, canvas, x, y):

        """This is the top level function, which

        draws the drawing at the given location.

        The recursive part is handled by drawNode."""

        self.undefined("draw")

    def drawNode(self, node):

        """This is the recursive method called for each node

        in the tree"""

        # Undefined here, but with closer analysis probably can be handled in superclass

        self.undefined("drawNode")

    def drawNodeDispatcher(self, node):

        """dispatch on the node's (super) class: shared code"""

        #print "drawNodeDispatcher", self, node.__class__

        # replace UserNode with its contents

        if isinstance(node, UserNode):

            node = node.provideNode()

        #draw the object, or recurse

        if isinstance(node, Line):

            self.drawLine(node)

        elif isinstance(node, Rect):

            self.drawRect(node)

        elif isinstance(node, Circle):

            self.drawCircle(node)

        elif isinstance(node, Ellipse):

            self.drawEllipse(node)

        elif isinstance(node, PolyLine):

            self.drawPolyLine(node)

        elif isinstance(node, Polygon):

            self.drawPolygon(node)

        elif isinstance(node, Path):

            self.drawPath(node)

        elif isinstance(node, String):

            self.drawString(node)

        elif isinstance(node, Group):

            for childNode in node.contents:

                self.drawNode(childNode)

        elif isinstance(node, Wedge):

            #print "drawWedge"

            self.drawWedge(node)

        else:

            print 'DrawingError','Unexpected element %s in pingo drawing!' % str(node)

        #print "done dispatching"

    _restores = {'stroke':'_stroke','stroke_width': '_lineWidth','stroke_linecap':'_lineCap',

                'stroke_linejoin':'_lineJoin','fill':'_fill','font_family':'_font',

                'font_size':'_fontSize'}

    def drawWedge(self, wedge):

        # by default ask the wedge to make a polygon of itself and draw that!

        #print "drawWedge"

        polygon = wedge.asPolygon()

        self.drawPolygon(polygon)

    def drawPath(self, path):

        polygons = path.asPolygons()

        for polygon in polygons:

                self.drawPolygon(polygon)

    def drawRect(self, rect):

        # could be implemented in terms of polygon

        self.undefined("drawRect")

    def drawLine(self, line):

        self.undefined("drawLine")

    def drawCircle(self, circle):

        self.undefined("drawCircle")

    def drawPolyLine(self, p):

        self.undefined("drawPolyLine")

    def drawEllipse(self, ellipse):

        self.undefined("drawEllipse")

    def drawPolygon(self, p):

        self.undefined("drawPolygon")

    def drawString(self, stringObj):

        self.undefined("drawString")

    def applyStateChanges(self, delta, newState):

        """This takes a set of states, and outputs the operators

        needed to set those properties"""

        self.undefined("applyStateChanges")

if __name__=='__main__':

    print "this file has no script interpretation"

    print __doc__