Add inner_corner default setting

to allow removing the loops in inner corners

Related: #294

boxes/__init__.py

@@ -298,6 +298,10 @@ class Boxes:
         defaultgroup.add_argument(
             "--reference", action="store", type=float, default=100,
             help="print reference rectangle with given length (in mm)(zero to disable) [\U0001F6C8](https://florianfesti.github.io/boxes/html/usermanual.html#reference)")
+        defaultgroup.add_argument(
+            "--inner_corners", action="store", type=str, default="loop",
+            choices=["loop", "corner", "backarc"],
+            help="style for inner corners [\U0001F6C8](https://florianfesti.github.io/boxes/html/usermanual.html#inner-corners)")
         defaultgroup.add_argument(
             "--burn", action="store", type=float, default=0.1,
             help='burn correction (in mm)(bigger values for tighter fit) [\U0001F6C8](https://florianfesti.github.io/boxes/html/usermanual.html#burn)')
@@ -671,7 +675,7 @@ class Boxes:
         self.surface.set_metadata(self.metadata)
 
         self.surface.flush()
-        self.surface.finish()
+        self.surface.finish(self.inner_corners)
 
         self.formats.convert(self.output, self.format, self.metadata)
         if self.inkscapefile:

boxes/drawing.py

@@ -186,7 +186,10 @@ class Path:
                 if invert_y:
                     c[3] *= Affine.scale(1, -1)
 
-    def faster_edges(self):
+    def faster_edges(self, inner_corners):
+        if inner_corners == "backarc":
+            return
+
         for (i, p) in enumerate(self.path):
             if p[0] == "C" and i > 1 and i < len(self.path) - 1:
                 if self.path[i - 1][0] == "L" and self.path[i + 1][0] == "L":
@@ -200,8 +203,12 @@ class Path:
                     lines_intersect, x, y = line_intersection((p11, p12), (p21, p22))
                     if lines_intersect:
                         self.path[i - 1] = ("L", x, y)
-                        self.path[i] = ("C", x, y, *p12, *p21)
-
+                        if inner_corners == "loop":
+                            self.path[i] = ("C", x, y, *p12, *p21)
+                        else:
+                            self.path[i] =  ("L", x, y)
+        # filter duplicates
+        self.path = [p for n, p in enumerate(self.path) if p != self.path[n-1]]
 
 class Context:
     def __init__(self, surface, *al, **ad):
@@ -460,7 +467,7 @@ Creation date: {date}
         m.tail = '\n'
         root.insert(0, m)
 
-    def finish(self):
+    def finish(self, inner_corners="loop"):
         extents = self._adjust_coordinates()
         w = extents.width * self.scale
         h = extents.height * self.scale
@@ -498,7 +505,7 @@ Creation date: {date}
                 x, y = 0, 0
                 start = None
                 last = None
-                path.faster_edges()
+                path.faster_edges(inner_corners)
                 for c in path.path:
                     x0, y0 = x, y
                     C, x, y = c[0:3]
@@ -602,7 +609,7 @@ class PSSurface(Surface):
             desc += f'%%SettingsUrl: {md["url"].replace("&render=1", "")}\n'
         return desc
 
-    def finish(self):
+    def finish(self, inner_corners="loop"):
 
         extents = self._adjust_coordinates()
         w = extents.width
@@ -644,7 +651,7 @@ class PSSurface(Surface):
             for j, path in enumerate(part.pathes):
                 p = []
                 x, y = 0, 0
-                path.faster_edges()
+                path.faster_edges(inner_corners)
 
                 for c in path.path:
                     x0, y0 = x, y

documentation/src/faq.rst

@@ -32,12 +32,12 @@ Unfortunately some formats do not save the units of measurement or don't do so p
 Why are there tiny, weird loops in the corners?
 -----------------------------------------------
 
-These are called dog bones and make sure the corner is completely cut out. As lasers and milling tools are round they can't cut sharp inner corners. Have a look at :doc:`burn correction details <api_burn>`.
+These are called dog bones and make sure the corner is completely cut out. As lasers and milling tools are round they can't cut sharp inner corners. Have a look at :doc:`burn correction details <api_burn>` for details.
 
 I really don't want those weird, tiny loops?
 --------------------------------------------
 
-You can just set ``burn`` to ``0`` to make them go away. But you have then to use a separate CAM software to do the burn correction (aka kerf). Or your laser cutter software may be able to take care of that.
+You can set the ``inner_corners`` default setting to ``corner``
 
 What settings were used to generate a drawing?
 ----------------------------------------------

documentation/src/usermanual.rst

@@ -117,6 +117,21 @@ For plywood values of 0.2 to 0.3mm still allow getting the parts out
 by hand (Depending on you laser cutter and the exact material). With
 little more you will need a knife to cut them loose. 
 
+inner_corners
+.............
+
+How to handle inner corners. Inner corners are an issue as a round
+tool like a laser or mill cannot create sharp inner corners. There are
+different options:
+
+* ``loop`` create a loop that fills the corner
+* ``corner`` just a simple sharp corner in the path that will leave a
+  radius untouched.
+* ``backarc`` naive implementation with inverted arcs connection the
+  straight lines.
+
+See also :doc:`burn correction details <api_burn>`
+
 debug
 .....