change templates to call modal_handler_add() is called last since any errors between calling this function and returning will crash blender. see [#30687]

release/scripts/startup/bl_operators/wm.py

@@ -735,7 +735,7 @@ class WM_OT_context_modal_mouse(Operator):
 
         if not self._values:
             self.report({'WARNING'}, "Nothing to operate on: %s[ ].%s" %
-                    (self.data_path_iter, self.data_path_item))
+                        (self.data_path_iter, self.data_path_item))
 
             return {'CANCELLED'}
         else:

release/scripts/templates/operator_modal.py

@@ -26,9 +26,10 @@ class ModalOperator(bpy.types.Operator):
 
     def invoke(self, context, event):
         if context.object:
-            context.window_manager.modal_handler_add(self)
             self.first_mouse_x = event.mouse_x
             self.first_value = context.object.location.x
+
+            context.window_manager.modal_handler_add(self)
             return {'RUNNING_MODAL'}
         else:
             self.report({'WARNING'}, "No active object, could not finish")

release/scripts/templates/operator_modal_draw.py

@@ -53,14 +53,13 @@ class ModalDrawOperator(bpy.types.Operator):
 
     def invoke(self, context, event):
         if context.area.type == 'VIEW_3D':
-            context.window_manager.modal_handler_add(self)
-
             # Add the region OpenGL drawing callback
             # draw in view space with 'POST_VIEW' and 'PRE_VIEW'
             self._handle = context.region.callback_add(draw_callback_px, (self, context), 'POST_PIXEL')
 
             self.mouse_path = []
 
+            context.window_manager.modal_handler_add(self)
             return {'RUNNING_MODAL'}
         else:
             self.report({'WARNING'}, "View3D not found, cannot run operator")

release/scripts/templates/operator_modal_timer.py

@@ -21,8 +21,8 @@ class ModalTimerOperator(bpy.types.Operator):
         return {'PASS_THROUGH'}
 
     def execute(self, context):
-        context.window_manager.modal_handler_add(self)
         self._timer = context.window_manager.event_timer_add(0.1, context.window)
+        context.window_manager.modal_handler_add(self)
         return {'RUNNING_MODAL'}
 
     def cancel(self, context):

release/scripts/templates/operator_modal_view3d.py

@@ -45,14 +45,13 @@ class ViewOperator(bpy.types.Operator):
             v3d = context.space_data
             rv3d = v3d.region_3d
 
-            context.window_manager.modal_handler_add(self)
-
             if rv3d.view_perspective == 'CAMERA':
                 rv3d.view_perspective = 'PERSP'
 
             self._initial_mouse = Vector((event.mouse_x, event.mouse_y, 0.0))
             self._initial_location = rv3d.view_location.copy()
 
+            context.window_manager.modal_handler_add(self)
             return {'RUNNING_MODAL'}
         else:
             self.report({'WARNING'}, "Active space must be a View3d")

source/blender/windowmanager/intern/wm_event_system.c

@@ -1444,14 +1444,15 @@ static int wm_handler_operator_call(bContext *C, ListBase *handlers, wmEventHand
 			
 		}
 		else {
-			printf("%s: error - missing modal\n", __func__);
+			printf("%s: error '%s' missing modal\n", __func__, op->idname);
 		}
 	}
 	else {
 		wmOperatorType *ot = WM_operatortype_find(event->keymap_idname, 0);
 
-		if (ot)
+		if (ot) {
 			retval = wm_operator_invoke(C, ot, event, properties, NULL, FALSE);
+		}
 	}
 	/* Finished and pass through flag as handled */