SVG not valid - wrong tag in svg.py

[mkurz4]

Describe the bug SvgBackend produces a svg file with a tag named "" which is wrong and should be re-named to "" according to https://developer.mozilla.org/en-US/docs/Web/SVG/Element/defs

The incorrect tag leads to style classes beeing not applied in some SVG viewers (or if you use reportlab). Geometries are filled although fill is set to none.

If you open the svg and replace "def" with "defs", then all works in reportlab and some other svg viewers.

Needed change: ezdxf/addons/drawings/svg.py:220 - rename "def" to "defs"

To Reproduce ezdxf 1.3.3 reportlab 4.2.2

`import ezdxf from ezdxf.addons.drawing import RenderContext, svg, Frontend, layout from reportlab.pdfgen import canvas from reportlab.graphics import renderPDF from svglib.svglib import svg2rlg from ezdxf.addons.drawing import config as ezdxf_config

dxf_doc = ezdxf.new("AC1015", setup=True) msp = dxf_doc.modelspace()

boundary = [ [0., 0.], [1., 0.], [1., 1.], [0., 1.], ]

msp.add_lwpolyline(boundary, close=True)

1. create the render context

context = RenderContext(dxf_doc, export_mode=False)

2. create the backend

backend = svg.SVGBackend()

create a new configuration for a white background

cfg = ezdxf_config.Configuration( color_policy=ezdxf_config.ColorPolicy.COLOR, background_policy=ezdxf_config.BackgroundPolicy.WHITE, )

3. create the frontend

frontend = Frontend(context, backend, config=cfg)

4. draw the modelspace

frontend.draw_layout(msp)

5. create an A4 page layout, not required for all backends

page = layout.Page( 100, 100, layout.Units.mm, margins=layout.Margins.all(2), max_width=100, max_height=100, )

svg file

file = "tmp.svg"

with open(file, "w") as f: f.write(backend.get_string(page))

reportlab pdf

drawing=svg2rlg(file) drawing.scale(0.3, 0.3)

c = canvas.Canvas('tmp.pdf') renderPDF.draw(drawing,c, 10, 40) c.showPage() c.save() `

Screenshots erroneous: working: