Remove circular reference between Graph and FilterContext

av/filter/context.pxd

@@ -7,7 +7,7 @@ from av.filter.graph cimport Graph
 cdef class FilterContext:
 
     cdef lib.AVFilterContext *ptr
-    cdef readonly Graph graph
+    cdef readonly object _graph
     cdef readonly Filter filter
 
     cdef object _inputs

av/filter/context.pyi

@@ -1,3 +1,4 @@
+from av.filter import Graph
 from av.frame import Frame
 
 from .pad import FilterContextPad
@@ -11,5 +12,7 @@ class FilterContext:
     def link_to(
         self, input_: FilterContext, output_idx: int = 0, input_idx: int = 0
     ) -> None: ...
+    @property
+    def graph(self) -> Graph: ...
     def push(self, frame: Frame) -> None: ...
     def pull(self) -> Frame: ...

av/filter/context.pyx

@@ -1,3 +1,5 @@
+import weakref
+
 from av.audio.frame cimport alloc_audio_frame
 from av.dictionary cimport _Dictionary
 from av.dictionary import Dictionary
@@ -13,7 +15,7 @@ cdef object _cinit_sentinel = object()
 
 cdef FilterContext wrap_filter_context(Graph graph, Filter filter, lib.AVFilterContext *ptr):
     cdef FilterContext self = FilterContext(_cinit_sentinel)
-    self.graph = graph
+    self._graph = weakref.ref(graph)
     self.filter = filter
     self.ptr = ptr
     return self
@@ -72,6 +74,13 @@ cdef class FilterContext:
 
     def link_to(self, FilterContext input_, int output_idx=0, int input_idx=0):
         err_check(lib.avfilter_link(self.ptr, output_idx, input_.ptr, input_idx))
+
+    @property
+    def graph(self):
+        if (graph := self._graph()):
+            return graph
+        else:
+            raise RuntimeError("graph is unallocated")
 
     def push(self, Frame frame):
         cdef int res

av/filter/graph.pxd

@@ -4,6 +4,8 @@ from av.filter.context cimport FilterContext
 
 
 cdef class Graph:
+    cdef object __weakref__
+
     cdef lib.AVFilterGraph *ptr
 
     cdef readonly bint configured