Use edgeSelected with passing shape as second argument

labelme/app.py

@@ -481,7 +481,7 @@ class MainWindow(QtWidgets.QMainWindow):
             onShapesPresent=(saveAs, hideAll, showAll),
         )
 
-        self.canvas.possibleToAddPoint.connect(self.actions.addPointToEdge.setEnabled)
+        self.canvas.edgeSelected.connect(self.canvasShapeEdgeSelected)
 
         self.menus = utils.struct(
             file=self.menu('&File'),
@@ -718,6 +718,11 @@ class MainWindow(QtWidgets.QMainWindow):
         for action in self.actions.onLoadActive:
             action.setEnabled(value)
 
+    def canvasShapeEdgeSelected(self, selected, shape):
+        self.actions.addPointToEdge.setEnabled(
+            selected and shape and shape.canAddPoint()
+        )
+
     def queueEvent(self, function):
         QtCore.QTimer.singleShot(0, function)
 

labelme/widgets/canvas.py

@@ -26,7 +26,7 @@ class Canvas(QtWidgets.QWidget):
     selectionChanged = QtCore.Signal(list)
     shapeMoved = QtCore.Signal()
     drawingPolygon = QtCore.Signal(bool)
-    possibleToAddPoint = QtCore.Signal(bool)
+    edgeSelected = QtCore.Signal(bool, object)
 
     CREATE, EDIT = 0, 1
 
@@ -267,7 +267,7 @@ class Canvas(QtWidgets.QWidget):
                 self.hShape.highlightClear()
                 self.update()
             self.hVertex, self.hShape, self.hEdge = None, None, None
-        self.possibleToAddPoint.emit(self.hEdge is not None and self.hShape is not None and self.hShape.canAddPoint())
+        self.edgeSelected.emit(self.hEdge is not None, self.hShape)
 
     def addPointToEdge(self):
         if (self.hShape is None and