1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148

//! Convenience logic for turning components from the main world into extracted
//! instances in the render world.
//!
//! This is essentially the same as the `extract_component` module, but
//! higher-performance because it avoids the ECS overhead.

use std::marker::PhantomData;

use bevy_app::{App, Plugin};
use bevy_asset::{Asset, AssetId, Handle};
use bevy_derive::{Deref, DerefMut};
use bevy_ecs::{
    entity::EntityHashMap,
    prelude::Entity,
    query::{QueryFilter, QueryItem, ReadOnlyQueryData},
    system::{lifetimeless::Read, Query, ResMut, Resource},
};

use crate::{prelude::ViewVisibility, Extract, ExtractSchedule, RenderApp};

/// Describes how to extract data needed for rendering from a component or
/// components.
///
/// Before rendering, any applicable components will be transferred from the
/// main world to the render world in the [`ExtractSchedule`] step.
///
/// This is essentially the same as
/// [`ExtractComponent`](crate::extract_component::ExtractComponent), but
/// higher-performance because it avoids the ECS overhead.
pub trait ExtractInstance: Send + Sync + Sized + 'static {
    /// ECS [`ReadOnlyQueryData`] to fetch the components to extract.
    type QueryData: ReadOnlyQueryData;
    /// Filters the entities with additional constraints.
    type QueryFilter: QueryFilter;

    /// Defines how the component is transferred into the "render world".
    fn extract(item: QueryItem<'_, Self::QueryData>) -> Option<Self>;
}

/// This plugin extracts one or more components into the "render world" as
/// extracted instances.
///
/// Therefore it sets up the [`ExtractSchedule`] step for the specified
/// [`ExtractedInstances`].
#[derive(Default)]
pub struct ExtractInstancesPlugin<EI>
where
    EI: ExtractInstance,
{
    only_extract_visible: bool,
    marker: PhantomData<fn() -> EI>,
}

/// Stores all extract instances of a type in the render world.
#[derive(Resource, Deref, DerefMut)]
pub struct ExtractedInstances<EI>(EntityHashMap<EI>)
where
    EI: ExtractInstance;

impl<EI> Default for ExtractedInstances<EI>
where
    EI: ExtractInstance,
{
    fn default() -> Self {
        Self(Default::default())
    }
}

impl<EI> ExtractInstancesPlugin<EI>
where
    EI: ExtractInstance,
{
    /// Creates a new [`ExtractInstancesPlugin`] that unconditionally extracts to
    /// the render world, whether the entity is visible or not.
    pub fn new() -> Self {
        Self {
            only_extract_visible: false,
            marker: PhantomData,
        }
    }

    /// Creates a new [`ExtractInstancesPlugin`] that extracts to the render world
    /// if and only if the entity it's attached to is visible.
    pub fn extract_visible() -> Self {
        Self {
            only_extract_visible: true,
            marker: PhantomData,
        }
    }
}

impl<EI> Plugin for ExtractInstancesPlugin<EI>
where
    EI: ExtractInstance,
{
    fn build(&self, app: &mut App) {
        if let Some(render_app) = app.get_sub_app_mut(RenderApp) {
            render_app.init_resource::<ExtractedInstances<EI>>();
            if self.only_extract_visible {
                render_app.add_systems(ExtractSchedule, extract_visible::<EI>);
            } else {
                render_app.add_systems(ExtractSchedule, extract_all::<EI>);
            }
        }
    }
}

fn extract_all<EI>(
    mut extracted_instances: ResMut<ExtractedInstances<EI>>,
    query: Extract<Query<(Entity, EI::QueryData), EI::QueryFilter>>,
) where
    EI: ExtractInstance,
{
    extracted_instances.clear();
    for (entity, other) in &query {
        if let Some(extract_instance) = EI::extract(other) {
            extracted_instances.insert(entity, extract_instance);
        }
    }
}

fn extract_visible<EI>(
    mut extracted_instances: ResMut<ExtractedInstances<EI>>,
    query: Extract<Query<(Entity, &ViewVisibility, EI::QueryData), EI::QueryFilter>>,
) where
    EI: ExtractInstance,
{
    extracted_instances.clear();
    for (entity, view_visibility, other) in &query {
        if view_visibility.get() {
            if let Some(extract_instance) = EI::extract(other) {
                extracted_instances.insert(entity, extract_instance);
            }
        }
    }
}

impl<A> ExtractInstance for AssetId<A>
where
    A: Asset,
{
    type QueryData = Read<Handle<A>>;
    type QueryFilter = ();

    fn extract(item: QueryItem<'_, Self::QueryData>) -> Option<Self> {
        Some(item.id())
    }
}