Merge pull request #83 from rezural/harness-testbed-integration

Harness testbed integration

14 files changed, 300 insertions, 296 deletions

diff --git a/examples2d/add_remove2.rs b/examples2d/add_remove2.rs
index a3d223d..0aeffbe 100644
--- a/examples2d/add_remove2.rs
+++ b/examples2d/add_remove2.rs
@@ -10,7 +10,7 @@ pub fn init_world(testbed: &mut Testbed) {
     let rad = 0.5;
 
     // Callback that will be executed on the main loop to handle proximities.
-    testbed.add_callback(move |window, physics, _, graphics, _| {
+    testbed.add_callback(move |mut window, mut graphics, physics, _, _| {
         let rigid_body = RigidBodyBuilder::new_dynamic()
             .translation(0.0, 10.0)
             .build();
@@ -19,7 +19,10 @@ pub fn init_world(testbed: &mut Testbed) {
         physics
             .colliders
             .insert(collider, handle, &mut physics.bodies);
-        graphics.add(window, handle, &physics.bodies, &physics.colliders);
+
+        if let (Some(graphics), Some(window)) = (&mut graphics, &mut window) {
+            graphics.add(*window, handle, &physics.bodies, &physics.colliders);
+        }
 
         let to_remove: Vec<_> = physics
             .bodies
@@ -31,7 +34,10 @@ pub fn init_world(testbed: &mut Testbed) {
             physics
                 .bodies
                 .remove(handle, &mut physics.colliders, &mut physics.joints);
-            graphics.remove_body_nodes(window, handle);
+
+            if let (Some(graphics), Some(window)) = (&mut graphics, &mut window) {
+                graphics.remove_body_nodes(*window, handle);
+            }
         }
     });
 
diff --git a/examples2d/platform2.rs b/examples2d/platform2.rs
index 20b2e59..afd4d64 100644
--- a/examples2d/platform2.rs
+++ b/examples2d/platform2.rs
@@ -60,13 +60,13 @@ pub fn init_world(testbed: &mut Testbed) {
     /*
      * Setup a callback to control the platform.
      */
-    testbed.add_callback(move |_, physics, _, _, time| {
+    testbed.add_callback(move |_, _, physics, _, run_state| {
         let platform = physics.bodies.get_mut(platform_handle).unwrap();
         let mut next_pos = *platform.position();
 
         let dt = 0.016;
-        next_pos.translation.vector.y += (time * 5.0).sin() * dt;
-        next_pos.translation.vector.x += time.sin() * 5.0 * dt;
+        next_pos.translation.vector.y += (run_state.time * 5.0).sin() * dt;
+        next_pos.translation.vector.x += run_state.time.sin() * 5.0 * dt;
 
         if next_pos.translation.vector.x >= rad * 10.0 {
             next_pos.translation.vector.x -= dt;
diff --git a/examples2d/sensor2.rs b/examples2d/sensor2.rs
index 959ecbf..3d5976d 100644
--- a/examples2d/sensor2.rs
+++ b/examples2d/sensor2.rs
@@ -69,7 +69,7 @@ pub fn init_world(testbed: &mut Testbed) {
     testbed.set_body_color(sensor_handle, Point3::new(0.5, 1.0, 1.0));
 
     // Callback that will be executed on the main loop to handle proximities.
-    testbed.add_callback(move |_, physics, events, graphics, _| {
+    testbed.add_callback(move |_, mut graphics, physics, events, _| {
         while let Ok(prox) = events.proximity_events.try_recv() {
             let color = match prox.new_status {
                 Proximity::WithinMargin | Proximity::Intersecting => Point3::new(1.0, 1.0, 0.0),
@@ -78,12 +78,13 @@ pub fn init_world(testbed: &mut Testbed) {
 
             let parent_handle1 = physics.colliders.get(prox.collider1).unwrap().parent();
             let parent_handle2 = physics.colliders.get(prox.collider2).unwrap().parent();
-
-            if parent_handle1 != ground_handle && parent_handle1 != sensor_handle {
-                graphics.set_body_color(parent_handle1, color);
-            }
-            if parent_handle2 != ground_handle && parent_handle2 != sensor_handle {
-                graphics.set_body_color(parent_handle2, color);
+            if let Some(graphics) = &mut graphics {
+                if parent_handle1 != ground_handle && parent_handle1 != sensor_handle {
+                    graphics.set_body_color(parent_handle1, color);
+                }
+                if parent_handle2 != ground_handle && parent_handle2 != sensor_handle {
+                    graphics.set_body_color(parent_handle2, color);
+                }
             }
         }
     });
diff --git a/examples3d/debug_add_remove_collider3.rs b/examples3d/debug_add_remove_collider3.rs
index a42dc97..f353162 100644
--- a/examples3d/debug_add_remove_collider3.rs
+++ b/examples3d/debug_add_remove_collider3.rs
@@ -34,7 +34,7 @@ pub fn init_world(testbed: &mut Testbed) {
     let collider = ColliderBuilder::ball(ball_rad).density(100.0).build();
     colliders.insert(collider, ball_handle, &mut bodies);
 
-    testbed.add_callback(move |window, physics, _, graphics, _| {
+    testbed.add_callback(move |mut window, mut graphics, physics, _, _| {
         // Remove then re-add the ground collider.
         let coll = physics
             .colliders
@@ -43,7 +43,10 @@ pub fn init_world(testbed: &mut Testbed) {
         ground_collider_handle = physics
             .colliders
             .insert(coll, ground_handle, &mut physics.bodies);
-        graphics.add_collider(window, ground_collider_handle, &physics.colliders);
+
+        if let (Some(graphics), Some(window)) = (&mut graphics, &mut window) {
+            graphics.add_collider(window, ground_collider_handle, &physics.colliders);
+        }
     });
 
     /*
diff --git a/examples3d/debug_dynamic_collider_add3.rs b/examples3d/debug_dynamic_collider_add3.rs
index a71e95e..bd7205e 100644
--- a/examples3d/debug_dynamic_collider_add3.rs
+++ b/examples3d/debug_dynamic_collider_add3.rs
@@ -45,7 +45,7 @@ pub fn init_world(testbed: &mut Testbed) {
     let mut extra_colliders = Vec::new();
     let snapped_frame = 51;
 
-    testbed.add_callback(move |window, physics, _, graphics, _| {
+    testbed.add_callback(move |mut window, mut graphics, physics, _, _| {
         step += 1;
 
         // Add a bigger ball collider
@@ -56,7 +56,11 @@ pub fn init_world(testbed: &mut Testbed) {
             physics
                 .colliders
                 .insert(collider, ball_handle, &mut physics.bodies);
-        graphics.add_collider(window, new_ball_collider_handle, &physics.colliders);
+
+        if let (Some(graphics), Some(window)) = (&mut graphics, &mut window) {
+            graphics.add_collider(window, new_ball_collider_handle, &physics.colliders);
+        }
+
         extra_colliders.push(new_ball_collider_handle);
 
         // Snap the ball velocity or restore it.
@@ -95,7 +99,11 @@ pub fn init_world(testbed: &mut Testbed) {
             physics
                 .colliders
                 .insert(coll, ground_handle, &mut physics.bodies);
-        graphics.add_collider(window, new_ground_collider_handle, &physics.colliders);
+
+        if let (Some(graphics), Some(window)) = (&mut graphics, &mut window) {
+            graphics.add_collider(window, new_ground_collider_handle, &physics.colliders);
+        }
+
         extra_colliders.push(new_ground_collider_handle);
     });
 
diff --git a/examples3d/debug_rollback3.rs b/examples3d/debug_rollback3.rs
index 19f9474..27b27cf 100644
--- a/examples3d/debug_rollback3.rs
+++ b/examples3d/debug_rollback3.rs
@@ -44,7 +44,7 @@ pub fn init_world(testbed: &mut Testbed) {
     let mut step = 0;
     let snapped_frame = 51;
 
-    testbed.add_callback(move |_, physics, _, _, _| {
+    testbed.add_callback(move |_, _, physics, _, _| {
         step += 1;
 
         // Snap the ball velocity or restore it.
diff --git a/examples3d/fountain3.rs b/examples3d/fountain3.rs
index fafa988..5acc2e8 100644
--- a/examples3d/fountain3.rs
+++ b/examples3d/fountain3.rs
@@ -26,7 +26,7 @@ pub fn init_world(testbed: &mut Testbed) {
     let mut k = 0;
 
     // Callback that will be executed on the main loop to handle proximities.
-    testbed.add_callback(move |window, physics, _, graphics, _| {
+    testbed.add_callback(move |mut window, mut graphics, physics, _, _| {
         k += 1;
         let rigid_body = RigidBodyBuilder::new_dynamic()
             .translation(0.0, 10.0, 0.0)
@@ -41,7 +41,10 @@ pub fn init_world(testbed: &mut Testbed) {
         physics
             .colliders
             .insert(collider, handle, &mut physics.bodies);
-        graphics.add(window, handle, &physics.bodies, &physics.colliders);
+
+        if let (Some(graphics), Some(window)) = (&mut graphics, &mut window) {
+            graphics.add(window, handle, &physics.bodies, &physics.colliders);
+        }
 
         if physics.bodies.len() > MAX_NUMBER_OF_BODIES {
             let mut to_remove: Vec<_> = physics
@@ -67,7 +70,10 @@ pub fn init_world(testbed: &mut Testbed) {
                 physics
                     .narrow_phase
                     .maintain(&mut physics.colliders, &mut physics.bodies);
-                graphics.remove_body_nodes(window, *handle);
+
+                if let (Some(graphics), Some(window)) = (&mut graphics, &mut window) {
+                    graphics.remove_body_nodes(window, *handle);
+                }
             }
         }
     });
diff --git a/examples3d/platform3.rs b/examples3d/platform3.rs
index 0975f39..7b5c986 100644
--- a/examples3d/platform3.rs
+++ b/examples3d/platform3.rs
@@ -65,7 +65,7 @@ pub fn init_world(testbed: &mut Testbed) {
      * Setup a callback to control the platform.
      */
     let mut count = 0;
-    testbed.add_callback(move |_, physics, _, _, time| {
+    testbed.add_callback(move |_, _, physics, _, run_state| {
         count += 1;
         if count % 100 > 50 {
             return;
@@ -75,8 +75,8 @@ pub fn init_world(testbed: &mut Testbed) {
             let mut next_pos = *platform.position();
 
             let dt = 0.016;
-            next_pos.translation.vector.y += (time * 5.0).sin() * dt;
-            next_pos.translation.vector.z += time.sin() * 5.0 * dt;
+            next_pos.translation.vector.y += (run_state.time * 5.0).sin() * dt;
+            next_pos.translation.vector.z += run_state.time.sin() * 5.0 * dt;
 
             if next_pos.translation.vector.z >= rad * 10.0 {
                 next_pos.translation.vector.z -= dt;
diff --git a/examples3d/sensor3.rs b/examples3d/sensor3.rs
index 7b218fe..4160248 100644
--- a/examples3d/sensor3.rs
+++ b/examples3d/sensor3.rs
@@ -73,7 +73,7 @@ pub fn init_world(testbed: &mut Testbed) {
     testbed.set_body_color(sensor_handle, Point3::new(0.5, 1.0, 1.0));
 
     // Callback that will be executed on the main loop to handle proximities.
-    testbed.add_callback(move |_, physics, events, graphics, _| {
+    testbed.add_callback(move |_, mut graphics, physics, events, _| {
         while let Ok(prox) = events.proximity_events.try_recv() {
             let color = match prox.new_status {
                 Proximity::WithinMargin | Proximity::Intersecting => Point3::new(1.0, 1.0, 0.0),
@@ -83,11 +83,13 @@ pub fn init_world(testbed: &mut Testbed) {
             let parent_handle1 = physics.colliders.get(prox.collider1).unwrap().parent();
             let parent_handle2 = physics.colliders.get(prox.collider2).unwrap().parent();
 
-            if parent_handle1 != ground_handle && parent_handle1 != sensor_handle {
-                graphics.set_body_color(parent_handle1, color);
-            }
-            if parent_handle2 != ground_handle && parent_handle2 != sensor_handle {
-                graphics.set_body_color(parent_handle2, color);
+            if let Some(graphics) = &mut graphics {
+                if parent_handle1 != ground_handle && parent_handle1 != sensor_handle {
+                    graphics.set_body_color(parent_handle1, color);
+                }
+                if parent_handle2 != ground_handle && parent_handle2 != sensor_handle {
+                    graphics.set_body_color(parent_handle2, color);
+                }
             }
         }
     });
diff --git a/src_testbed/harness/mod.rs b/src_testbed/harness/mod.rs
index fa6c4c6..51bf315 100644
--- a/src_testbed/harness/mod.rs
+++ b/src_testbed/harness/mod.rs
@@ -1,4 +1,8 @@
-use crate::physics::{PhysicsEvents, PhysicsState};
+use crate::{
+    physics::{PhysicsEvents, PhysicsState},
+    GraphicsManager,
+};
+use kiss3d::window::Window;
 use plugin::HarnessPlugin;
 use rapier::dynamics::{IntegrationParameters, JointSet, RigidBodySet};
 use rapier::geometry::{BroadPhase, ColliderSet, NarrowPhase};
@@ -7,24 +11,58 @@ use rapier::pipeline::{ChannelEventCollector, PhysicsPipeline, QueryPipeline};
 
 pub mod plugin;
 
-pub struct HarnessState {
+pub struct RunState {
     #[cfg(feature = "parallel")]
     pub thread_pool: rapier::rayon::ThreadPool,
+    #[cfg(feature = "parallel")]
+    pub num_threads: usize,
     pub timestep_id: usize,
+    pub time: f32,
+}
+
+impl RunState {
+    pub fn new() -> Self {
+        #[cfg(feature = "parallel")]
+        let num_threads = num_cpus::get_physical();
+
+        #[cfg(feature = "parallel")]
+        let thread_pool = rapier::rayon::ThreadPoolBuilder::new()
+            .num_threads(num_threads)
+            .build()
+            .unwrap();
+
+        Self {
+            #[cfg(feature = "parallel")]
+            thread_pool: thread_pool,
+            #[cfg(feature = "parallel")]
+            num_threads,
+            timestep_id: 0,
+            time: 0.0,
+        }
+    }
 }
 
 pub struct Harness {
-    physics: PhysicsState,
+    pub physics: PhysicsState,
     max_steps: usize,
     callbacks: Callbacks,
     plugins: Vec<Box<dyn HarnessPlugin>>,
-    time: f32,
     events: PhysicsEvents,
     event_handler: ChannelEventCollector,
-    pub state: HarnessState,
+    pub state: RunState,
 }
 
-type Callbacks = Vec<Box<dyn FnMut(&mut PhysicsState, &PhysicsEvents, &HarnessState, f32)>>;
+type Callbacks = Vec<
+    Box<
+        dyn FnMut(
+            Option<&mut Window>,
+            Option<&mut GraphicsManager>,
+            &mut PhysicsState,
+            &PhysicsEvents,
+            &RunState,
+        ),
+    >,
+>;
 
 #[allow(dead_code)]
 impl Harness {
@@ -46,18 +84,13 @@ impl Harness {
             proximity_events: proximity_channel.1,
         };
         let physics = PhysicsState::new();
-        let state = HarnessState {
-            #[cfg(feature = "parallel")]
-            thread_pool,
-            timestep_id: 0,
-        };
+        let state = RunState::new();
 
         Self {
             physics,
             max_steps: 1000,
             callbacks: Vec::new(),
             plugins: Vec::new(),
-            time: 0.0,
             events,
             event_handler,
             state,
@@ -101,7 +134,6 @@ impl Harness {
         self.physics.joints = joints;
         self.physics.broad_phase = BroadPhase::new();
         self.physics.narrow_phase = NarrowPhase::new();
-        self.time = 0.0;
         self.state.timestep_id = 0;
         self.physics.query_pipeline = QueryPipeline::new();
         self.physics.pipeline = PhysicsPipeline::new();
@@ -113,7 +145,13 @@ impl Harness {
     }
 
     pub fn add_callback<
-        F: FnMut(&mut PhysicsState, &PhysicsEvents, &HarnessState, f32) + 'static,
+        F: FnMut(
+                Option<&mut Window>,
+                Option<&mut GraphicsManager>,
+                &mut PhysicsState,
+                &PhysicsEvents,
+                &RunState,
+            ) + 'static,
     >(
         &mut self,
         callback: F,
@@ -122,6 +160,14 @@ impl Harness {
     }
 
     pub fn step(&mut self) {
+        self.step_with_graphics(None, None);
+    }
+
+    pub fn step_with_graphics(
+        &mut self,
+        window: Option<&mut Window>,
+        graphics: Option<&mut GraphicsManager>,
+    ) {
         #[cfg(feature = "parallel")]
         {
             let physics = &mut self.physics;
@@ -161,26 +207,44 @@ impl Harness {
             .update(&self.physics.bodies, &self.physics.colliders);
 
         for plugin in &mut self.plugins {
-            plugin.step(&mut self.physics)
+            plugin.step(&mut self.physics, &self.state)
         }
 
-        for f in &mut self.callbacks {
-            f(&mut self.physics, &self.events, &self.state, self.time)
+        // FIXME: This assumes either window & graphics are Some, or they are all None
+        // this is required as we cannot pass Option<&mut Window> & Option<&mut GraphicsManager directly in a loop
+        // there must be a better way of doing this?
+        match (window, graphics) {
+            (Some(window), Some(graphics)) => {
+                for f in &mut self.callbacks {
+                    f(
+                        Some(window),
+                        Some(graphics),
+                        &mut self.physics,
+                        &self.events,
+                        &self.state,
+                    );
+                }
+            }
+            _ => {
+                for f in &mut self.callbacks {
+                    f(None, None, &mut self.physics, &self.events, &self.state);
+                }
+            }
         }
 
         for plugin in &mut self.plugins {
-            plugin.run_callbacks(&mut self.physics, &self.events, &self.state, self.time)
+            plugin.run_callbacks(&mut self.physics, &self.events, &self.state)
         }
 
         self.events.poll_all();
 
-        self.time += self.physics.integration_parameters.dt();
+        self.state.time += self.physics.integration_parameters.dt();
+        self.state.timestep_id += 1;
     }
 
     pub fn run(&mut self) {
         for _ in 0..self.max_steps {
             self.step();
-            self.state.timestep_id += 1;
         }
     }
 }
diff --git a/src_testbed/harness/plugin.rs b/src_testbed/harness/plugin.rs
index 078219e..ac20945 100644
--- a/src_testbed/harness/plugin.rs
+++ b/src_testbed/harness/plugin.rs
@@ -1,4 +1,4 @@
-use crate::harness::HarnessState;
+use crate::harness::RunState;
 use crate::physics::PhysicsEvents;
 use crate::PhysicsState;
 
@@ -7,9 +7,8 @@ pub trait HarnessPlugin {
         &mut self,
         physics: &mut PhysicsState,
         events: &PhysicsEvents,
-        harness_state: &HarnessState,
-        t: f32,
+        harness_state: &RunState,
     );
-    fn step(&mut self, physics: &mut PhysicsState);
+    fn step(&mut self, physics: &mut PhysicsState, run_state: &RunState);
     fn profiling_string(&self) -> String;
 }
diff --git a/src_testbed/plugin.rs b/src_testbed/plugin.rs
index 872cdf5..877e7f6 100644
--- a/src_testbed/plugin.rs
+++ b/src_testbed/plugin.rs
@@ -1,3 +1,4 @@
+use crate::harness::RunState;
 use crate::physics::PhysicsState;
 use kiss3d::window::Window;
 use na::Point3;
@@ -5,7 +6,12 @@ use na::Point3;
 pub trait TestbedPlugin {
     fn init_graphics(&mut self, window: &mut Window, gen_color: &mut dyn FnMut() -> Point3<f32>);
     fn clear_graphics(&mut self, window: &mut Window);
-    fn run_callbacks(&mut self, window: &mut Window, physics: &mut PhysicsState, t: f32);
+    fn run_callbacks(
+        &mut self,
+        window: &mut Window,
+        physics: &mut PhysicsState,
+        run_state: &RunState,
+    );
     fn step(&mut self, physics: &mut PhysicsState);
     fn draw(&mut self);
     fn profiling_string(&self) -> String;
diff --git a/src_testbed/testbed.rs b/src_testbed/testbed.rs
index 4fac8e1..fd6b9a0 100644
--- a/src_testbed/testbed.rs
+++ b/src_testbed/testbed.rs
@@ -3,10 +3,10 @@ use std::mem;
 use std::path::Path;
 use std::rc::Rc;
 
-use crate::engine::GraphicsManager;
 use crate::physics::{PhysicsEvents, PhysicsSnapshot, PhysicsState};
 use crate::plugin::TestbedPlugin;
 use crate::ui::TestbedUi;
+use crate::{engine::GraphicsManager, harness::RunState};
 
 use kiss3d::camera::Camera;
 use kiss3d::event::Event;
@@ -21,14 +21,14 @@ use na::{self, Point2, Point3, Vector3};
 use rapier::dynamics::{
     ActivationStatus, IntegrationParameters, JointSet, RigidBodyHandle, RigidBodySet,
 };
-use rapier::geometry::{BroadPhase, ColliderHandle, ColliderSet, NarrowPhase};
+use rapier::geometry::{ColliderHandle, ColliderSet, NarrowPhase};
 #[cfg(feature = "dim3")]
 use rapier::geometry::{InteractionGroups, Ray};
 use rapier::math::Vector;
-use rapier::pipeline::{ChannelEventCollector, PhysicsPipeline, QueryPipeline};
 
 #[cfg(all(feature = "dim2", feature = "other-backends"))]
 use crate::box2d_backend::Box2dWorld;
+use crate::harness::Harness;
 #[cfg(feature = "other-backends")]
 use crate::nphysics_backend::NPhysicsWorld;
 #[cfg(all(feature = "dim3", feature = "other-backends"))]
@@ -114,30 +114,22 @@ pub struct TestbedState {
     pub selected_example: usize,
     pub selected_backend: usize,
     pub physx_use_two_friction_directions: bool,
-    pub num_threads: usize,
     pub snapshot: Option<PhysicsSnapshot>,
-    #[cfg(feature = "parallel")]
-    pub thread_pool: rapier::rayon::ThreadPool,
-    pub timestep_id: usize,
 }
 
 pub struct Testbed {
     builders: Vec<(&'static str, fn(&mut Testbed))>,
-    physics: PhysicsState,
     graphics: GraphicsManager,
     nsteps: usize,
     camera_locked: bool, // Used so that the camera can remain the same before and after we change backend or press the restart button.
-    callbacks: Callbacks,
     plugins: Vec<Box<dyn TestbedPlugin>>,
-    time: f32,
     hide_counters: bool,
     //    persistant_contacts: HashMap<ContactId, bool>,
     font: Rc<Font>,
     cursor_pos: Point2<f32>,
-    events: PhysicsEvents,
-    event_handler: ChannelEventCollector,
     ui: Option<TestbedUi>,
     state: TestbedState,
+    harness: Harness,
     #[cfg(all(feature = "dim2", feature = "other-backends"))]
     box2d: Option<Box2dWorld>,
     #[cfg(all(feature = "dim3", feature = "other-backends"))]
@@ -146,9 +138,6 @@ pub struct Testbed {
     nphysics: Option<NPhysicsWorld>,
 }
 
-type Callbacks =
-    Vec<Box<dyn FnMut(&mut Window, &mut PhysicsState, &PhysicsEvents, &mut GraphicsManager, f32)>>;
-
 impl Testbed {
     pub fn new_empty() -> Testbed {
         let graphics = GraphicsManager::new();
@@ -166,17 +155,6 @@ impl Testbed {
         #[cfg(all(feature = "dim3", feature = "other-backends"))]
         backend_names.push("physx (two friction dir)");
 
-        #[cfg(feature = "parallel")]
-        let num_threads = num_cpus::get_physical();
-        #[cfg(not(feature = "parallel"))]
-        let num_threads = 1;
-
-        #[cfg(feature = "parallel")]
-        let thread_pool = rapier::rayon::ThreadPoolBuilder::new()
-            .num_threads(num_threads)
-            .build()
-            .unwrap();
-
         let state = TestbedState {
             running: RunMode::Running,
             draw_colls: false,
@@ -193,40 +171,25 @@ impl Testbed {
             backend_names,
             example_names: Vec::new(),
             selected_example: 0,
-            timestep_id: 0,
             selected_backend: RAPIER_BACKEND,
             physx_use_two_friction_directions: true,
-            num_threads,
-            #[cfg(feature = "parallel")]
-            thread_pool,
         };
 
-        let contact_channel = crossbeam::channel::unbounded();
-        let proximity_channel = crossbeam::channel::unbounded();
-        let event_handler = ChannelEventCollector::new(proximity_channel.0, contact_channel.0);
-        let events = PhysicsEvents {
-            contact_events: contact_channel.1,
-            proximity_events: proximity_channel.1,
-        };
-        let physics = PhysicsState::new();
+        let harness = Harness::new_empty();
 
         Testbed {
             builders: Vec::new(),
-            physics,
-            callbacks: Vec::new(),
             plugins: Vec::new(),
             graphics,
             nsteps: 1,
             camera_locked: false,
-            time: 0.0,
             hide_counters: true,
             //            persistant_contacts: HashMap::new(),
             font: Font::default(),
             cursor_pos: Point2::new(0.0f32, 0.0),
             ui,
-            event_handler,
-            events,
             state,
+            harness,
             #[cfg(all(feature = "dim2", feature = "other-backends"))]
             box2d: None,
             #[cfg(all(feature = "dim3", feature = "other-backends"))]
@@ -238,7 +201,7 @@ impl Testbed {
 
     pub fn new(bodies: RigidBodySet, colliders: ColliderSet, joints: JointSet) -> Self {
         let mut res = Self::new_empty();
-        res.set_world(bodies, colliders, joints);
+        res.harness.set_world(bodies, colliders, joints);
         res
     }
 
@@ -269,11 +232,15 @@ impl Testbed {
     }
 
     pub fn integration_parameters_mut(&mut self) -> &mut IntegrationParameters {
-        &mut self.physics.integration_parameters
+        &mut self.harness.physics.integration_parameters
     }
 
     pub fn physics_state_mut(&mut self) -> &mut PhysicsState {
-        &mut self.physics
+        &mut self.harness.physics
+    }
+
+    pub fn harness_mut(&mut self) -> &mut Harness {
+        &mut self.harness
     }
 
     pub fn set_world(&mut self, bodies: RigidBodySet, colliders: ColliderSet, joints: JointSet) {
@@ -289,30 +256,23 @@ impl Testbed {
     ) {
         println!("Num bodies: {}", bodies.len());
         println!("Num joints: {}", joints.len());
-        self.physics.gravity = gravity;
-        self.physics.bodies = bodies;
-        self.physics.colliders = colliders;
-        self.physics.joints = joints;
-        self.physics.broad_phase = BroadPhase::new();
-        self.physics.narrow_phase = NarrowPhase::new();
+        self.harness
+            .set_world_with_gravity(bodies, colliders, joints, gravity);
+
         self.state
             .action_flags
             .set(TestbedActionFlags::RESET_WORLD_GRAPHICS, true);
-        self.time = 0.0;
-        self.state.timestep_id = 0;
+
         self.state.highlighted_body = None;
-        self.physics.query_pipeline = QueryPipeline::new();
-        self.physics.pipeline = PhysicsPipeline::new();
-        self.physics.pipeline.counters.enable();
 
         #[cfg(all(feature = "dim2", feature = "other-backends"))]
         {
             if self.state.selected_backend == BOX2D_BACKEND {
                 self.box2d = Some(Box2dWorld::from_rapier(
-                    self.physics.gravity,
-                    &self.physics.bodies,
-                    &self.physics.colliders,
-                    &self.physics.joints,
+                    physics.gravity,
+                    &physics.bodies,
+                    &physics.colliders,
+                    &physics.joints,
                 ));
             }
         }
@@ -323,13 +283,13 @@ impl Testbed {
                 || self.state.selected_backend == PHYSX_BACKEND_TWO_FRICTION_DIR
             {
                 self.physx = Some(PhysxWorld::from_rapier(
-                    self.physics.gravity,
-                    &self.physics.integration_parameters,
-                    &self.physics.bodies,
-                    &self.physics.colliders,
-                    &self.physics.joints,
+                    physics.gravity,
+                    &physics.integration_parameters,
+                    &physics.bodies,
+                    &physics.colliders,
+                    &physics.joints,
                     self.state.selected_backend == PHYSX_BACKEND_TWO_FRICTION_DIR,
-                    self.state.num_threads,
+                    self.harness.state.num_threads,
                 ));
             }
         }
@@ -338,10 +298,10 @@ impl Testbed {
         {
             if self.state.selected_backend == NPHYSICS_BACKEND {
                 self.nphysics = Some(NPhysicsWorld::from_rapier(
-                    self.physics.gravity,
-                    &self.physics.bodies,
-                    &self.physics.colliders,
-                    &self.physics.joints,
+                    physics.gravity,
+                    &physics.bodies,
+                    &physics.colliders,
+                    &physics.joints,
                 ));
             }
         }
@@ -419,7 +379,6 @@ impl Testbed {
     }
 
     fn clear(&mut self, window: &mut Window) {
-        self.callbacks.clear();
         //        self.persistant_contacts.clear();
         //        self.state.grabbed_object = None;
         //        self.state.grabbed_object_constraint = None;
@@ -433,17 +392,23 @@ impl Testbed {
         self.plugins.clear();
     }
 
-    pub fn add_plugin(&mut self, plugin: impl TestbedPlugin + 'static) {
-        self.plugins.push(Box::new(plugin));
-    }
-
     pub fn add_callback<
-        F: FnMut(&mut Window, &mut PhysicsState, &PhysicsEvents, &mut GraphicsManager, f32) + 'static,
+        F: FnMut(
+                Option<&mut Window>,
+                Option<&mut GraphicsManager>,
+                &mut PhysicsState,
+                &PhysicsEvents,
+                &RunState,
+            ) + 'static,
     >(
         &mut self,
         callback: F,
     ) {
-        self.callbacks.push(Box::new(callback));
+        self.harness.add_callback(callback);
+    }
+
+    pub fn add_plugin(&mut self, plugin: impl TestbedPlugin + 'static) {
+        self.plugins.push(Box::new(plugin));
     }
 
     pub fn run(mut self) {
@@ -464,6 +429,7 @@ impl Testbed {
             }
         }
 
+        // TODO: move this to dedicated benchmarking code
         if benchmark_mode {
             use std::fs::File;
             use std::io::{BufWriter, Write};
@@ -484,11 +450,23 @@ impl Testbed {
                         && (backend_id == PHYSX_BACKEND_PATCH_FRICTION
                             || backend_id == PHYSX_BACKEND_TWO_FRICTION_DIR)
                     {
-                        self.physics.integration_parameters.max_velocity_iterations = 1;
-                        self.physics.integration_parameters.max_position_iterations = 4;
+                        self.harness
+                            .physics
+                            .integration_parameters
+                            .max_velocity_iterations = 1;
+                        self.harness
+                            .physics
+                            .integration_parameters
+                            .max_position_iterations = 4;
                     } else {
-                        self.physics.integration_parameters.max_velocity_iterations = 4;
-                        self.physics.integration_parameters.max_position_iterations = 1;
+                        self.harness
+                            .physics
+                            .integration_parameters
+                            .max_velocity_iterations = 4;
+                        self.harness
+                            .physics
+                            .integration_parameters
+                            .max_position_iterations = 1;
                     }
                     // Init world.
                     (builder.1)(&mut self);
@@ -496,57 +474,20 @@ impl Testbed {
                     let mut timings = Vec::new();
                     for k in 0..=NUM_ITERS {
                         {
-                            // FIXME: code duplicated from self.step()
                             if self.state.selected_backend == RAPIER_BACKEND {
-                                #[cfg(feature = "parallel")]
-                                {
-                                    let physics = &mut self.physics;
-                                    let event_handler = &self.event_handler;
-                                    self.state.thread_pool.install(|| {
-                                        physics.pipeline.step(
-                                            &physics.gravity,
-                                            &physics.integration_parameters,
-                                            &mut physics.broad_phase,