pyx/canvasitem.py

   1 # -*- encoding: utf-8 -*-
   2 #
   3 #
   4 # Copyright (C) 2002-2007 Jörg Lehmann <joergl@users.sourceforge.net>
   5 # Copyright (C) 2002-2007 André Wobst <wobsta@users.sourceforge.net>
   6 #
   7 # This file is part of PyX (http://pyx.sourceforge.net/).
   8 #
   9 # PyX is free software; you can redistribute it and/or modify
  10 # it under the terms of the GNU General Public License as published by
  11 # the Free Software Foundation; either version 2 of the License, or
  12 # (at your option) any later version.
  13 #
  14 # PyX is distributed in the hope that it will be useful,
  15 # but WITHOUT ANY WARRANTY; without even the implied warranty of
  16 # MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  17 # GNU General Public License for more details.
  18 #
  19 # You should have received a copy of the GNU General Public License
  20 # along with PyX; if not, write to the Free Software
  21 # Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301, USA
  22
  23 class canvasitem:
  24
  25     """Base class for everything which can be inserted into a canvas"""
  26
  27     def bbox(self):
  28         """return bounding box of canvasitem"""
  29         # TODO: we either should raise a NotImplementedError here or return
  30         # an empty bounding box instance, as adding empty to a bouding box is
  31         # allowed. (We could also alter the merging behavior of bboxes to allow
  32         # None. Currently, canvasitem instances not overwriting this bbox method
  33         # lead to an error.)
  34         pass
  35
  36     def processPS(self, file, writer, context, registry, bbox):
  37         """process canvasitem by writing the corresponding PS code to file and
  38         by updating context, registry as well as bbox
  39
  40         - the PS code corresponding to the canvasitem has to be written in the
  41           stream file, which provides a write(string) method
  42         - writer is the PSwriter used for the output
  43         - context is an instance of pswriter.context which is used for keeping
  44           track of the graphics state (current linewidth, colorspace and font))
  45         - registry is used for tracking resources needed by the canvasitem
  46         - bbox has to be updated to include the bounding box of the canvasitem
  47         """
  48         raise NotImplementedError()
  49
  50     def processPDF(self, file, writer, context, registry, bbox):
  51         """process canvasitem by writing the corresponding PDF code to file and
  52         by updating context, registry as well as bbox
  53
  54         - the PDF code corresponding to the canvasitem has to be written in the
  55           stream file, which provides a write(string) method
  56         - writer is the PDFwriter used for the output, which contains properties
  57           like whether streamcompression is used
  58         - context is an instance of pdfwriter.context which is used for keeping
  59           track of the graphics state, in particular for the emulation of PS
  60           behaviour regarding fill and stroke styles, for keeping track of the
  61           currently selected font as well as of text regions.
  62         - registry is used for tracking resources needed by the canvasitem
  63         - bbox has to be updated to include the bounding box of the canvasitem
  64         """
  65         raise NotImplementedError()