From 00f0b06afc8b8ed22873d1a4be1232a3b8c3a0e1 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Mariusz=20Kry=C5=84ski?= <mrk@sed.pl>
Date: Sun, 11 Oct 2020 20:54:47 +0200
Subject: [PATCH] defer render systems until render resource context is ready

---
 crates/bevy_ecs/src/resource/resource_query.rs      | 13 +++++++++++++
 crates/bevy_render/src/pipeline/render_pipelines.rs |  3 ++-
 crates/bevy_render/src/render_graph/system.rs       |  4 ++++
 crates/bevy_ui/src/widget/text.rs                   |  3 ++-
 4 files changed, 21 insertions(+), 2 deletions(-)

diff --git a/crates/bevy_ecs/src/resource/resource_query.rs b/crates/bevy_ecs/src/resource/resource_query.rs
index ab33775bce0e6..cf18a1c1344b7 100644
--- a/crates/bevy_ecs/src/resource/resource_query.rs
+++ b/crates/bevy_ecs/src/resource/resource_query.rs
@@ -209,6 +209,10 @@ impl<'a, T: Resource> FetchResource<'a> for FetchResourceRead<T> {
         Res::new(resources.get_unsafe_ref::<T>(ResourceIndex::Global))
     }
 
+    unsafe fn is_some(resources: &'a Resources, _system_id: Option<SystemId>) -> bool {
+        resources.contains::<T>()
+    }
+
     fn borrow(resources: &Resources) {
         resources.borrow::<T>();
     }
@@ -276,6 +280,10 @@ impl<'a, T: Resource> FetchResource<'a> for FetchResourceWrite<T> {
         ResMut::new(value, type_state.mutated())
     }
 
+    unsafe fn is_some(resources: &'a Resources, _system_id: Option<SystemId>) -> bool {
+        resources.contains::<T>()
+    }
+
     fn borrow(resources: &Resources) {
         resources.borrow_mut::<T>();
     }
@@ -322,6 +330,11 @@ impl<'a, T: Resource + FromResources> FetchResource<'a> for FetchResourceLocalMu
         }
     }
 
+    unsafe fn is_some(resources: &'a Resources, system_id: Option<SystemId>) -> bool {
+        let id = system_id.expect("Local<T> resources can only be used by systems");
+        resources.get_local::<T>(id).is_some()
+    }
+
     fn borrow(resources: &Resources) {
         resources.borrow_mut::<T>();
     }
diff --git a/crates/bevy_render/src/pipeline/render_pipelines.rs b/crates/bevy_render/src/pipeline/render_pipelines.rs
index 875c6d94bc848..aa764dc4d6b9f 100644
--- a/crates/bevy_render/src/pipeline/render_pipelines.rs
+++ b/crates/bevy_render/src/pipeline/render_pipelines.rs
@@ -3,7 +3,7 @@ use crate::{
     draw::{Draw, DrawContext},
     mesh::{Indices, Mesh},
     prelude::Msaa,
-    renderer::RenderResourceBindings,
+    renderer::{RenderResourceBindings, RenderResourceContext},
 };
 use bevy_asset::{Assets, Handle};
 use bevy_ecs::{Query, Res, ResMut};
@@ -73,6 +73,7 @@ impl Default for RenderPipelines {
 }
 
 pub fn draw_render_pipelines_system(
+    _render_resource_context: Res<Box<dyn RenderResourceContext>>,
     mut draw_context: DrawContext,
     mut render_resource_bindings: ResMut<RenderResourceBindings>,
     msaa: Res<Msaa>,
diff --git a/crates/bevy_render/src/render_graph/system.rs b/crates/bevy_render/src/render_graph/system.rs
index 330be0a1f9baa..afda924710ac2 100644
--- a/crates/bevy_render/src/render_graph/system.rs
+++ b/crates/bevy_render/src/render_graph/system.rs
@@ -1,7 +1,11 @@
 use super::RenderGraph;
+use crate::renderer::RenderResourceContext;
 use bevy_ecs::{Resources, World};
 
 pub fn render_graph_schedule_executor_system(world: &mut World, resources: &mut Resources) {
+    if resources.get::<Box<dyn RenderResourceContext>>().is_none() {
+        return;
+    }
     // run render graph systems
     let (mut system_schedule, commands) = {
         let mut render_graph = resources.get_mut::<RenderGraph>().unwrap();
diff --git a/crates/bevy_ui/src/widget/text.rs b/crates/bevy_ui/src/widget/text.rs
index 6b2f5c1133025..b05092130fba8 100644
--- a/crates/bevy_ui/src/widget/text.rs
+++ b/crates/bevy_ui/src/widget/text.rs
@@ -6,7 +6,7 @@ use bevy_render::{
     draw::{Draw, DrawContext, Drawable},
     mesh::Mesh,
     prelude::Msaa,
-    renderer::{AssetRenderResourceBindings, RenderResourceBindings},
+    renderer::{AssetRenderResourceBindings, RenderResourceBindings, RenderResourceContext},
     texture::Texture,
 };
 use bevy_sprite::{TextureAtlas, QUAD_HANDLE};
@@ -90,6 +90,7 @@ pub fn text_system(
 
 #[allow(clippy::too_many_arguments)]
 pub fn draw_text_system(
+    _render_resource_context: Res<Box<dyn RenderResourceContext>>,
     mut draw_context: DrawContext,
     fonts: Res<Assets<Font>>,
     msaa: Res<Msaa>,