From 8c40ff39d7ef7278878b4da4a55f67d69b62be57 Mon Sep 17 00:00:00 2001
From: rdb <git@rdb.name>
Date: Fri, 23 Aug 2019 12:04:26 +0200
Subject: [PATCH] bullet: fix contact added callback behavior

The API seems to imply that the callback is per-world, when it is actually a global setting.  This fixes it to truly behave per-world.  This also fixes a crash on shutdown caused by the callback destructing when the Python interpreter is already shutting down.

Fixes #712
---
 panda/src/bullet/bulletWorld.cxx | 8 ++++++--
 panda/src/bullet/bulletWorld.h   | 1 +
 2 files changed, 7 insertions(+), 2 deletions(-)

diff --git a/panda/src/bullet/bulletWorld.cxx b/panda/src/bullet/bulletWorld.cxx
index 930fe10111..6fa0381949 100644
--- a/panda/src/bullet/bulletWorld.cxx
+++ b/panda/src/bullet/bulletWorld.cxx
@@ -222,6 +222,8 @@ int BulletWorld::
 do_physics(PN_stdfloat dt, int max_substeps, PN_stdfloat stepsize) {
   LightMutexHolder holder(get_global_lock());
 
+  bullet_contact_added_callback = _contact_added_callback_obj;
+
   _pstat_physics.start();
 
   int num_substeps = clamp(int(dt / stepsize), 1, max_substeps);
@@ -249,6 +251,8 @@ do_physics(PN_stdfloat dt, int max_substeps, PN_stdfloat stepsize) {
 
   _pstat_physics.stop();
 
+  bullet_contact_added_callback.clear();
+
   return n;
 }
 
@@ -1146,7 +1150,7 @@ set_contact_added_callback(CallbackObject *obj) {
   _world->getSolverInfo().m_solverMode |= SOLVER_USE_2_FRICTION_DIRECTIONS;
   _world->getSolverInfo().m_solverMode |= SOLVER_ENABLE_FRICTION_DIRECTION_CACHING;
 
-  bullet_contact_added_callback = obj;
+  _contact_added_callback_obj = obj;
 }
 
 /**
@@ -1160,7 +1164,7 @@ clear_contact_added_callback() {
   _world->getSolverInfo().m_solverMode &= ~SOLVER_USE_2_FRICTION_DIRECTIONS;
   _world->getSolverInfo().m_solverMode &= ~SOLVER_ENABLE_FRICTION_DIRECTION_CACHING;
 
-  bullet_contact_added_callback = nullptr;
+  _contact_added_callback_obj = nullptr;
 }
 
 /**
diff --git a/panda/src/bullet/bulletWorld.h b/panda/src/bullet/bulletWorld.h
index 67607923dd..bc032f1934 100644
--- a/panda/src/bullet/bulletWorld.h
+++ b/panda/src/bullet/bulletWorld.h
@@ -272,6 +272,7 @@ private:
   btOverlapFilterCallback *_filter_cb;
 
   PT(CallbackObject) _tick_callback_obj;
+  PT(CallbackObject) _contact_added_callback_obj;
 
   PT(BulletDebugNode) _debug;