bernhard: thuban/Extensions/svgexport svgmapwriter.py,1.8,1.9

[cvs@intevation.de]

Author: bernhard

Update of /thubanrepository/thuban/Extensions/svgexport
In directory doto:/tmp/cvs-serv29643/Extensions/svgexport

Modified Files:
	svgmapwriter.py 
Log Message:
	* Doc/technotes/coding_guidelines.txt: easy typo fixed. 

	* Extensions/svgexport/test/test_svgmapwriter.py:
	Removed test_drawbezier in favour of new test_drawspline3 and 
	test_drawspline4 within new class TestDrawSplines(TestVirtualDC).
	All only to test DrawSpline.

	* Extensions/svgexport/svgmapwriter.py(DrawSpline):
	New implementation now really using the strange algorithm of
	xfig 3.1's approximated splines and its conversion to postscript
	with one twist: SVG can do quadratic beziers, so skipped translation
	to cubic beziers.
	(TestWithDC): Typo in comment fixed.


Index: svgmapwriter.py
===================================================================
RCS file: /thubanrepository/thuban/Extensions/svgexport/svgmapwriter.py,v
retrieving revision 1.8
retrieving revision 1.9
diff -u -d -r1.8 -r1.9
--- svgmapwriter.py	7 Dec 2004 11:19:38 -0000	1.8
+++ svgmapwriter.py	11 Dec 2004 02:03:47 -0000	1.9
@@ -701,14 +701,50 @@
             self.make_meta(), join(data, '') ) )
 
     def DrawSpline(self, points, closed=0):
-        """Draw a spline object.
+        """Calculate square bezier points for an xfig approximated spline.
+
+        DrawSpline() needs to do the same as the function of the Device Context
+        of wxWidgets. Code inspection shows it uses the "approximated
+        splines" of xfig <= 3.1. This can be mapped 
+        on SVG's squared bezier curves,
+        by doing the same calculation like wxPostScriptDC::DoDrawSpline() in
+        wxWidgets src/generic/dcpsg.cpp.
+        Which is derived from xfig's 3.1.4 u_draw.c(draw_open_spline()).
+
+        And then leave out the last translation to cubic beziers
+        done in the postscript code of DrawSplineSection.
         """
         self.write_indent('<path %s ' % (self.make_style(1,1,0)))
         datastr = ""
-        # we have four points: start, control, control, end
-        datastr+=('M %s %s C' % (points[0].x, points[0].y))
-        for i in (1,2,3):
-            datastr+=(' %s %s' %  (points[i].x,points[i].y))
+
+        x1=points[0].x
+        y1=points[0].y
+
+        datastr+=('M %s %s ' % (x1, y1))
+
+        c=points[1].x
+        d=points[1].y
+
+        x3  = (x1 + c) / 2;
+        y3  = (y1 + d) / 2;
+
+        datastr+=('L %s %s ' % (x3,y3))
+
+        for point in points[2:]:
+            x2 = c
+            y2 = d
+            c = point.x
+            d = point.y
+            x3 = (x2 + c) / 2;
+            y3 = (y2 + d) / 2;
+
+            # With SVG's bezier commands, the last point becomes the next start
+            # so no new L necessary
+            # SVG Spec 1.1 recommends to not uses lines longer than 255 chars
+            datastr+=('Q %s %s %s %s\n' % (x2,y2,x3,y3))
+
+        datastr+=('L %s %s' % (c,d))
+
         self.file.write('%s %s d="%s"/>\n' % (self.make_id(), 
             self.make_meta(), datastr ) )