Add line width argument for SVG preview and export

boxes/__init__.py

@@ -408,6 +408,9 @@ def __init__(self) -> None:
         defaultgroup.add_argument(
             "--output", action="store", type=str, default="box.svg",
             help="name of resulting file")
+        defaultgroup.add_argument(
+            "--line_width", action="store", type=(lambda x: float('NaN') if x == "" else float(x)), default="",
+            help='line width for SVG preview and export (in mm) (default: 2x burn but at least 0.05) [\U0001F6C8](https://florianfesti.github.io/boxes/html/usermanual.html#line-width)')
         def spacing_type(x):
             try:
                 return (float(x), 0.)
@@ -464,7 +467,10 @@ def open(self):
             self.ctx.set_line_width(0.01)
             self.set_source_color(Color.BLUE)
         else:
-            self.ctx.set_line_width(max(2 * self.burn, 0.05))
+            line_width = self.line_width
+            if line_width != line_width:  # check for NaN (default)
+                line_width = max(2 * self.burn, 0.05)
+            self.ctx.set_line_width(line_width)
             self.set_source_color(Color.BLACK)
 
         self.spacing = 2 * self.burn + self.spacing[0] * self.thickness + self.spacing[1]

documentation/src/usermanual.rst

@@ -87,6 +87,14 @@ much smaller it is than its nominal size. The burn value should be
 around half of the difference. To test the fit for several values at
 once you can use the **BurnTest** generator in the "Parts and Samples" section.
 
+line_width
+..........
+
+The line width parameter defines how wide the lines in the SVG preview
+and download files are drawn. By default it is twice the burn value but
+at least 0.05mm. This paramteter allows to overwrite if required by some
+laser engraving software.
+
 spacing
 .......