feat(option): add curvestyle option (ortho or curved)

diagrams/__init__.py

@@ -39,6 +39,7 @@ def setcluster(cluster):
 
 class Diagram:
     __directions = ("TB", "BT", "LR", "RL")
+    __curvestyles = ("ortho", "curved")
     __outformats = ("png", "jpg", "svg", "pdf")
 
     # fmt: off
@@ -78,6 +79,7 @@ def __init__(
         name: str = "",
         filename: str = "",
         direction: str = "LR",
+        curvestyle: str = "ortho",
         outformat: str = "png",
         show: bool = True,
         graph_attr: dict = {},
@@ -91,6 +93,7 @@ def __init__(
         :param filename: The output filename, without the extension (.png).
             If not given, it will be generated from the name.
         :param direction: Data flow direction. Default is 'left to right'.
+        :param curvestyle: Curve bending style. One of "ortho" or "curved".
         :param outformat: Output file format. Default is 'png'.
         :param show: Open generated image after save if true, just only save otherwise.
         :param graph_attr: Provide graph_attr dot config attributes.
@@ -117,6 +120,10 @@ def __init__(
             raise ValueError(f'"{direction}" is not a valid direction')
         self.dot.graph_attr["rankdir"] = direction
 
+        if not self._validate_curvestyle(curvestyle):
+            raise ValueError(f'"{curvestyle}" is not a valid curvestyle')
+        self.dot.graph_attr["splines"] = curvestyle
+
         if not self._validate_outformat(outformat):
             raise ValueError(f'"{outformat}" is not a valid output format')
         self.outformat = outformat
@@ -151,6 +158,13 @@ def _validate_direction(self, direction: str) -> bool:
                 return True
         return False
 
+    def _validate_curvestyle(self, curvestyle: str) -> bool:
+        curvestyle = curvestyle.lower()
+        for v in self.__curvestyles:
+            if v == curvestyle:
+                return True
+        return False
+
     def _validate_outformat(self, outformat: str) -> bool:
         outformat = outformat.lower()
         for v in self.__outformats:

tests/test_diagram.py

@@ -33,6 +33,16 @@ def test_validate_direction(self):
             with self.assertRaises(ValueError):
                 Diagram(direction=dir)
 
+    def test_validate_curvestyle(self):
+        # Normal directions.
+        for cvs in ("ortho", "curved"):
+            Diagram(curvestyle=cvs)
+
+        # Invalid directions.
+        for cvs in ("tangent", "unknown"):
+            with self.assertRaises(ValueError):
+                Diagram(curvestyle=cvs)
+
     def test_validate_outformat(self):
         # Normal output formats.
         for fmt in ("png", "jpg", "svg", "pdf"):