Add latest and earliest methods to events and begin camera system port

bevy_app/src/event.rs

@@ -112,7 +112,8 @@ where
         self.event_count += 1;
     }
 
-    /// Iterates over the events the `event_reader` has not seen yet.
+    /// Iterates over the events the `event_reader` has not seen yet. This updates the `event_reader`'s event counter,
+    /// which means subsequent event reads will not include events that happened before now.
     pub fn iter(&self, event_reader: &mut EventReader<T>) -> impl DoubleEndedIterator<Item = &T> {
         // if the reader has seen some of the events in a buffer, find the proper index offset.
         // otherwise read all events in the buffer
@@ -157,6 +158,30 @@ where
         }
     }
 
+    /// Retrieves the latest event. This updates the `event_reader`'s event counter,
+    /// which means subsequent event reads will not include events that happened before now.
+    pub fn latest(&self, event_reader: &mut EventReader<T>) -> Option<&T> {
+        self.iter(event_reader)
+            .rev()
+            .next()
+    }
+
+    /// Retrieves the latest event that matches the given `predicate`. This updates the `event_reader`'s event counter,
+    /// which means subsequent event reads will not include events that happened before now.
+    pub fn find_latest(&self, event_reader: &mut EventReader<T>, predicate: impl FnMut(&&T) -> bool) -> Option<&T> {
+        self.iter(event_reader)
+            .rev()
+            .filter(predicate)
+            .next()
+    }
+
+    /// Retrieves the earliest event. This updates the `event_reader`'s event counter,
+    /// which means subsequent event reads will not include events that happened before now.
+    pub fn earliest(&self, event_reader: &mut EventReader<T>) -> Option<&T> {
+        self.iter(event_reader)
+            .next()
+    }
+
     /// Gets a new [EventReader]. This will include all events already in the event buffers.
     pub fn get_reader(&self) -> EventReader<T> {
         EventReader {

bevy_render/src/camera.rs

@@ -126,12 +126,8 @@ pub fn camera_update_system(resources: &mut Resources) -> Box<dyn Schedulable> {
         .read_resource::<Events<WindowResized>>()
         .with_query(<Write<Camera>>::query())
         .build(move |_, world, window_resized_events, query| {
-            // TODO: refactor this to "window_resized_events.latest()"
             let primary_window_resized_event = window_resized_events
-                .iter(&mut window_resized_event_reader)
-                .rev()
-                .filter(|event| event.is_primary)
-                .next();
+                .find_latest(&mut window_resized_event_reader, |event| event.is_primary);
             if let Some(primary_window_resized_event) = primary_window_resized_event {
                 for mut camera in query.iter_mut(world) {
                     camera.update(

bevy_render/src/render_resource/resource_providers/camera2d_resource_provider.rs

@@ -56,10 +56,7 @@ impl ResourceProvider for Camera2dResourceProvider {
     ) {
         let window_resized_events = resources.get::<Events<WindowResized>>().unwrap();
         let primary_window_resized_event = window_resized_events
-            .iter(&mut self.window_resized_event_reader)
-            .rev()
-            .filter(|event| event.is_primary)
-            .next();
+            .find_latest(&mut self.window_resized_event_reader, |event| event.is_primary);
 
         if let Some(_) = primary_window_resized_event {
             let matrix_size = std::mem::size_of::<[[f32; 4]; 4]>();

bevy_render/src/render_resource/resource_providers/camera_resource_provider.rs

@@ -5,15 +5,81 @@ use crate::{
         resource_name, BufferInfo, BufferUsage, RenderResource, RenderResourceAssignments,
         ResourceProvider,
     },
-    renderer_2::RenderContext,
+    renderer_2::{GlobalRenderResourceContext, RenderContext},
     ActiveCamera, Camera,
 };
 
-use bevy_app::{EventReader, Events};
+use bevy_app::{EventReader, Events, GetEventReader};
 use bevy_transform::prelude::*;
 use legion::prelude::*;
 use zerocopy::AsBytes;
 
+pub fn camera_resource_provider_system(resources: &mut Resources) -> Box<dyn Schedulable> {
+    let mut camera_buffer = None;
+    let mut tmp_buffer = None;
+    let mut window_resized_event_reader = resources.get_event_reader::<WindowResized>();
+    SystemBuilder::new("mesh_resource_provider")
+        .read_resource::<GlobalRenderResourceContext>()
+        // TODO: this write on RenderResourceAssignments will prevent this system from running in parallel with other systems that do the same
+        .write_resource::<RenderResourceAssignments>()
+        .read_resource::<Events<WindowResized>>()
+        .with_query(<(Read<Camera>, Read<LocalToWorld>, Read<ActiveCamera>)>::query())
+        .build(
+            move |_,
+                  world,
+                  (
+                render_resource_context,
+                ref mut render_resource_assignments,
+                window_resized_events,
+            ),
+                  query| {
+                let render_resources = &render_resource_context.context;
+                if camera_buffer.is_none() {
+                    let buffer = render_resources.create_buffer(BufferInfo {
+                        size: std::mem::size_of::<[[f32; 4]; 4]>(),
+                        buffer_usage: BufferUsage::COPY_DST | BufferUsage::UNIFORM,
+                        ..Default::default()
+                    });
+                    render_resource_assignments.set(resource_name::uniform::CAMERA, buffer);
+                    camera_buffer = Some(buffer);
+                }
+
+                let primary_window_resized_event = window_resized_events
+                    .find_latest(&mut window_resized_event_reader, |event| event.is_primary);
+                if let Some(_) = primary_window_resized_event {
+                    let matrix_size = std::mem::size_of::<[[f32; 4]; 4]>();
+                    for (camera, local_to_world, _) in query.iter(world) {
+                        let camera_matrix: [[f32; 4]; 4] =
+                            (camera.view_matrix * local_to_world.0).to_cols_array_2d();
+
+                        if let Some(old_tmp_buffer) = tmp_buffer {
+                            render_resources.remove_buffer(old_tmp_buffer);
+                        }
+
+                        tmp_buffer = Some(render_resources.create_buffer_mapped(
+                            BufferInfo {
+                                size: matrix_size,
+                                buffer_usage: BufferUsage::COPY_SRC,
+                                ..Default::default()
+                            },
+                            &mut |data, _renderer| {
+                                data[0..matrix_size].copy_from_slice(camera_matrix.as_bytes());
+                            },
+                        ));
+
+                        // render_resources.copy_buffer_to_buffer(
+                        //     tmp_buffer.unwrap(),
+                        //     0,
+                        //     camera_buffer.unwrap(),
+                        //     0,
+                        //     matrix_size as u64,
+                        // );
+                    }
+                }
+            },
+        )
+}
+
 pub struct CameraResourceProvider {
     pub camera_buffer: Option<RenderResource>,
     pub tmp_buffer: Option<RenderResource>,
@@ -57,10 +123,9 @@ impl ResourceProvider for CameraResourceProvider {
     ) {
         let window_resized_events = resources.get::<Events<WindowResized>>().unwrap();
         let primary_window_resized_event = window_resized_events
-            .iter(&mut self.window_resized_event_reader)
-            .rev()
-            .filter(|event| event.is_primary)
-            .next();
+            .find_latest(&mut self.window_resized_event_reader, |event| {
+                event.is_primary
+            });
         if let Some(_) = primary_window_resized_event {
             let matrix_size = std::mem::size_of::<[[f32; 4]; 4]>();
             for (camera, local_to_world, _) in

bevy_render/src/render_resource/resource_providers/mesh_resource_provider.rs

@@ -35,6 +35,7 @@ pub fn mesh_resource_provider_system(resources: &mut Resources) -> Box<dyn Sched
                             )
                         } else {
                             let mesh_asset = meshes.get(&handle).unwrap();
+                            // TODO: use a staging buffer here
                             let vertex_buffer = render_resources.create_buffer_with_data(
                                 BufferInfo {
                                     buffer_usage: BufferUsage::VERTEX,