From 8e86cb4450db9e9de3cd9d1f6cb0d2d46bd6adf5 Mon Sep 17 00:00:00 2001
From: Sebastian Hamel <sebjfk@gmail.com>
Date: Sat, 16 Sep 2023 01:29:29 -0400
Subject: [PATCH] hide canvas when no render items are in scene

---
 Cargo.toml              |  2 +-
 src/lib.rs              |  8 +++++++-
 src/renderer/extract.rs | 36 ++++++++++++------------------------
 src/renderer/plugin.rs  |  3 +--
 src/rendertarget.rs     | 16 +++++++++++++++-
 5 files changed, 36 insertions(+), 29 deletions(-)

diff --git a/Cargo.toml b/Cargo.toml
index 491924b..e30883a 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -4,7 +4,7 @@ members = ["demo"]
 
 [workspace.package]
 edition = "2021"
-version = "0.3.1"
+version = "0.3.2"
 license = "MIT OR Apache-2.0"
 repository = "https://github.com/vectorgameexperts/bevy-vello"
 
diff --git a/src/lib.rs b/src/lib.rs
index c002417..bed9ea0 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -50,7 +50,13 @@ impl Plugin for BevyVelloPlugin {
             DebugVisualizationsPlugin,
         ));
         app.add_systems(Startup, rendertarget::setup_ss_rendertarget)
-            .add_systems(Update, rendertarget::resize_rendertargets);
+            .add_systems(
+                Update,
+                (
+                    rendertarget::resize_rendertargets,
+                    rendertarget::clear_when_empty,
+                ),
+            );
     }
 }
 
diff --git a/src/renderer/extract.rs b/src/renderer/extract.rs
index b818c7b..5d494af 100644
--- a/src/renderer/extract.rs
+++ b/src/renderer/extract.rs
@@ -6,21 +6,6 @@ use bevy::{
 
 use crate::{font::VelloFont, ColorPaletteSwap, Layer, VelloText, VelloVector};
 
-#[derive(Component)]
-pub struct RenderReadyTag;
-
-pub fn tag_vectors_for_render(
-    mut commands: Commands,
-    vector_assets: ResMut<Assets<VelloVector>>,
-    vectors: Query<(Entity, &Handle<VelloVector>), Without<RenderReadyTag>>,
-) {
-    for (entity, handle) in vectors.iter() {
-        if vector_assets.get(handle).is_some() {
-            commands.entity(entity).insert(RenderReadyTag);
-        }
-    }
-}
-
 #[derive(Component, Clone)]
 pub struct ExtractedRenderVector {
     pub vector_handle: Handle<VelloVector>,
@@ -40,22 +25,25 @@ pub fn vector_instances(
             &GlobalTransform,
             Option<&ColorPaletteSwap>,
             Option<&Node>,
+            &ComputedVisibility,
         )>,
     >,
     assets: Extract<Res<Assets<VelloVector>>>,
 ) {
-    for (vello_vector_handle, layer, transform, color_pallette_swap, ui_node) in
+    for (vello_vector_handle, layer, transform, color_pallette_swap, ui_node, visibility) in
         query_vectors.iter()
     {
         if let Some(asset_data) = assets.get(vello_vector_handle) {
-            commands.spawn(ExtractedRenderVector {
-                vector_handle: vello_vector_handle.clone(),
-                render_data: asset_data.to_owned(),
-                transform: *transform,
-                layer: *layer,
-                color_pallette_swap: color_pallette_swap.cloned(),
-                ui_node: ui_node.cloned(),
-            });
+            if visibility.is_visible() {
+                commands.spawn(ExtractedRenderVector {
+                    vector_handle: vello_vector_handle.clone(),
+                    render_data: asset_data.to_owned(),
+                    transform: *transform,
+                    layer: *layer,
+                    color_pallette_swap: color_pallette_swap.cloned(),
+                    ui_node: ui_node.cloned(),
+                });
+            }
         }
     }
 }
diff --git a/src/renderer/plugin.rs b/src/renderer/plugin.rs
index 55dc8d5..1f9850c 100644
--- a/src/renderer/plugin.rs
+++ b/src/renderer/plugin.rs
@@ -49,8 +49,7 @@ impl Plugin for VelloRenderPlugin {
             ExtractComponentPlugin::<extract::SSRenderTarget>::default(),
             RenderAssetPlugin::<VelloVector>::default(),
             RenderAssetPlugin::<VelloFont>::default(),
-        ))
-        .add_systems(Update, extract::tag_vectors_for_render);
+        ));
     }
 
     fn finish(&self, app: &mut App) {
diff --git a/src/rendertarget.rs b/src/rendertarget.rs
index 699a755..1854759 100644
--- a/src/rendertarget.rs
+++ b/src/rendertarget.rs
@@ -16,7 +16,7 @@ use bevy::{
     window::{WindowResized, WindowResolution},
 };
 
-use crate::{renderer::SSRenderTarget, SSRT_SHADER_HANDLE};
+use crate::{renderer::SSRenderTarget, Layer, SSRT_SHADER_HANDLE};
 
 #[derive(Component)]
 struct MainCamera;
@@ -195,3 +195,17 @@ impl Material2d for VelloCanvasMaterial {
         Ok(())
     }
 }
+
+/// Hide the RenderTarget canvas if there is nothing to render
+pub fn clear_when_empty(
+    mut query_render_target: Query<&mut Visibility, With<SSRenderTarget>>,
+    render_items: Query<(&mut Layer, &ComputedVisibility)>,
+) {
+    if let Ok(mut visibility) = query_render_target.get_single_mut() {
+        if render_items.is_empty() {
+            *visibility = Visibility::Hidden;
+        } else {
+            *visibility = Visibility::Inherited;
+        }
+    }
+}