reportlab/graphics/renderbase.py
changeset 568 9cadc5ef53db
child 580 62e61180ae41
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/reportlab/graphics/renderbase.py	Mon Jan 22 22:05:38 2001 +0000
@@ -0,0 +1,238 @@
+###############################################################################
+#   $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__