possibly a fix for inkscape 1.2.x

bubbles/bubbles.py

@@ -7,12 +7,11 @@ def __init__(self,
                  grad_offset=30.0,
                  font_family='Latin Modern Sans', font_weight='normal'):
         self.pars = locals(); self.pars.pop('self')
-        self.bubble = {}
-        self._bubbles  = []
+        self.bubble = {}  # bubble definitions
+        self._bubbles  = []  # bubble placements (id, x, y)
         self._liaisons = []
         self._texts    = []
-        self._colors   = []
-        self._colorsid = []
+        self._colors   = []  # color definition
 
     def def_bubble(self, key, fill=0xFFFFFF, r=50, stroke=0x990000, stroke_w=10):
 
@@ -140,12 +139,17 @@ def put_liaison_equal(self, r0, x, y0, y1, h):
         '''
 
         l = abs(y1-y0)
+        assert 0.5*h <= r0 , f"bad h parameter, should be less or equal to {2*r0}"
+        if 0.5*l < r0:
+            assert 0.25*(l**2+h**2) >= r0**2, f"bad h parameter, should be greater or equal to {2*math.sqrt(r0**2-l**2/4)}"
+
         R = (0.25*l**2 + 0.25*h**2 - r0**2) / (2.0*r0 - h)
 
         dx = 0.5*h + R
         dy = 0.5*l
         dr = math.hypot(dx, dy)
 
+        # position of a tangent point wrt C0's center
         xx = dx*r0 / dr
         yy = dy*r0 / dr
         return R, x+xx, y0+yy, 0,  2.0*(dy-yy), -2.0*xx
@@ -270,6 +274,7 @@ def get_canvsize(self):
 
 
 def _gold(f, eps, bra, ket):
+    """Golden ratio optimisation: find a local minimum for f between bra and key, with tolerence eps"""
     phi = (math.sqrt(5.0)-1.0)*0.5
     d   = ket-bra
     x1  = ket-d*phi

inkscape-ext/bubblebond.py

@@ -3,7 +3,16 @@
 from itertools import count
 import inkex
 from lxml import etree
-import bubbles
+
+try:
+    import bubbles
+except ImportError:
+    # try and detect the bubbles.py file next to this one
+    import sys, os
+    sys.path.append(os.path.split(__file__)[0])
+    import bubbles
+    del sys.path[-1]
+    del sys,os
 
 
 class BubbleBond(inkex.Effect):
@@ -36,7 +45,19 @@ def effect(self):
             raise inkex.AbortExtension("These are not circles.")
         h = width * 2.0*min(r0, r1)
 
-        colors = (st0['stroke'], st1['stroke'])
+        if 'stroke' in st0 and st0['stroke'] != 'none':
+            col0 = st0['stroke']
+        elif 'fill' in st0:
+            col0 = st0['fill']
+        else:
+            col0 = 'none'
+        if 'stroke' in st1 and st1['stroke'] != 'none':
+            col1 = st1['stroke']
+        elif 'fill' in st0:
+            col1 = st1['fill']
+        else:
+            col1 = 'none'
+        colors = (col0, col1)
         x0 = float(c0.attrib['cx'])
         y0 = float(c0.attrib['cy'])
         x1 = float(c1.attrib['cx'])
@@ -98,14 +119,19 @@ def get_radius(self, c0, st0):
             r0 = c0.radius[0]
         else:
             return None
-        return r0 + float(st0['stroke-width'])/2
+        if 'stroke' in st0 and st0['stroke'] != 'none':
+            return r0 + float(st0['stroke-width'])/2
+        else:
+            return r0
 
     def get_style_dict(self, c0):
         st0_str = c0.attrib['style']
         st0_obj = inkex.styles.Style.parse_str(st0_str)
-        st0_dict = {}
-        for key, val in st0_obj:
-            st0_dict[key] = val
+        if hasattr(st0_obj, 'items'):
+            st0_dict = { k:v for k,v in st0_obj.items() }
+        else:
+            # fallback that only works on old versions of inkscape (before which one?)
+            st0_dict = { k:v for k,v in st0_obj }
         return st0_dict