Refs #328 - Make <symbol> rendered only when referenced

CHANGELOG.rst

@@ -7,6 +7,8 @@ Unreleased
 ----------
 
 - Support mmult import from reportlab < 3.5.61 (#316).
+- ``<symbol>`` nodes now only appears in documents when they are
+  referenced, not on their initial appearance.
 
 1.2.1 (2022-01-27)
 ------------------

svglib/svglib.py

@@ -588,7 +588,12 @@ def renderNode(self, node, parent=None):
             self.renderStyle(n)
         elif name == "symbol":
             item = self.renderSymbol(n)
-            parent.add(item)
+            # First time the symbol node is rendered, it should not be part of a group.
+            # It is only rendered to be part of definitions.
+            if n.attrib.get('_rendered'):
+                parent.add(item)
+            else:
+                n.set('_rendered', '1')
         elif name == "use":
             item = self.renderUse(n, clipping=clipping)
             parent.add(item)
@@ -852,16 +857,14 @@ def renderSvg(self, node, outermost=False):
 
         return group
 
-    def renderG(self, node, clipping=None, display=1):
+    def renderG(self, node, clipping=None):
         getAttr = node.getAttribute
         id, transform = map(getAttr, ("id", "transform"))
         gr = Group()
         if clipping:
             gr.add(clipping)
         for child in node.getchildren():
-            item = self.renderNode(child, parent=gr)
-            if item and display:
-                gr.add(item)
+            self.renderNode(child, parent=gr)
 
         if transform:
             self.shape_converter.applyTransformOnGroup(transform, gr)
@@ -872,7 +875,7 @@ def renderStyle(self, node):
         self.attrConverter.css_rules.add_styles(node.text or "")
 
     def renderSymbol(self, node):
-        return self.renderG(node, display=0)
+        return self.renderG(node)
 
     def renderA(self, node):
         # currently nothing but a group...

tests/test_basic.py

@@ -938,6 +938,19 @@ def test_use_node_with_unclosed_path(self):
 
 
 class TestSymbolNode:
+    def test_symbol_unused(self):
+        """<symbol> by itself should not be rendered."""
+        drawing = svglib.svg2rlg(io.StringIO(textwrap.dedent('''\
+            <?xml version="1.0"?>
+            <svg xmlns="http://www.w3.org/2000/svg"
+                 width="900" height="600" viewBox="0 0 100 100">
+                <symbol id="X">
+                    <path d="M 0,0100 V 0 H 50"/>
+                </symbol>
+            </svg>
+        ''')))
+        assert drawing.contents[0].contents == []
+
     def test_symbol_node(self):
         drawing = svglib.svg2rlg(io.StringIO(textwrap.dedent('''\
             <?xml version="1.0"?>