merge: Implement two-point oblique vector snapping (#454)

capellambse/diagram/_diagram.py

@@ -16,6 +16,7 @@
 ]
 
 import collections.abc as cabc
+import contextlib
 import enum
 import logging
 import math
@@ -272,18 +273,20 @@ def vector_snap(
             source = diagram.Vector2D(*source)
 
         if style is RoutingStyle.OBLIQUE:
-            return self.__vector_snap_oblique(point)
+            if point == source:
+                return self.__vector_snap_closest(point)
+            return self.__vector_snap_oblique(point, source)
         if style is RoutingStyle.MANHATTAN:
             return self.__vector_snap_manhattan(point, point - source)
         if style is RoutingStyle.TREE:
             return self.__vector_snap_tree(point, point - source)
         raise ValueError(f"Unsupported routing style: {style}")
 
-    def __vector_snap_oblique(
+    def __vector_snap_closest(
         self, source: diagram.Vector2D
     ) -> diagram.Vector2D:
         if source == self.center:
-            return source
+            return self.pos + self.size @ (0, 0.5)
 
         angle = self.size.angleto(source - self.center)
         alpha = 2 * self.size.angleto((1, 0))
@@ -310,6 +313,61 @@ def __vector_snap_oblique(
             (self.pos, self.pos + self.size @ (0, 1)),
         )
 
+    def __vector_snap_oblique(
+        self, point: diagram.Vector2D, source: diagram.Vector2D
+    ) -> diagram.Vector2D:
+        assert point != source
+        if not (
+            self.pos.x <= point.x <= self.pos.x + self.size.x
+            and self.pos.y <= point.y <= self.pos.y + self.size.y
+        ):
+            point = self.center
+        direction = point - source
+        edge = (source, point)
+        assert direction.x or direction.y, f"{edge} doesn't have a direction"
+
+        edges: set[str] = set()
+        if direction.x > 0:
+            edges.add("left")
+        elif direction.x < 0:
+            edges.add("right")
+
+        if direction.y > 0:
+            edges.add("top")
+        elif direction.y < 0:
+            edges.add("bottom")
+        assert len(edges) in (1, 2), f"{edge} doesn't have a direction"
+
+        intersections: list[diagram.Vector2D] = []
+        if "top" in edges:
+            border = (self.pos, self.pos + self.size @ (1, 0))
+            with contextlib.suppress(ValueError):
+                intersection = diagram.line_intersect(border, edge)
+                if border[0].x <= intersection.x <= border[1].x:
+                    intersections.append(intersection)
+        if "left" in edges:
+            border = (self.pos, self.pos + self.size @ (0, 1))
+            with contextlib.suppress(ValueError):
+                intersection = diagram.line_intersect(border, edge)
+                if border[0].y <= intersection.y <= border[1].y:
+                    intersections.append(intersection)
+        if "right" in edges:
+            border = (self.pos + self.size @ (1, 0), self.pos + self.size)
+            with contextlib.suppress(ValueError):
+                intersection = diagram.line_intersect(border, edge)
+                if border[0].y <= intersection.y <= border[1].y:
+                    intersections.append(intersection)
+        if "bottom" in edges:
+            border = (self.pos + self.size @ (0, 1), self.pos + self.size)
+            with contextlib.suppress(ValueError):
+                intersection = diagram.line_intersect(border, edge)
+                if border[0].x <= intersection.x <= border[1].x:
+                    intersections.append(intersection)
+
+        assert len(intersections) > 0, f"{edge} doesn't intersect {edges}"
+        assert len(intersections) < 2, f"{edge} intersects multiple {edges}"
+        return intersections[0]
+
     def __vector_snap_manhattan(
         self, point: diagram.Vector2D, direction: diagram.Vector2D
     ) -> diagram.Vector2D: