bevy/crates/bevy_ui/src/widget/text.rs

use crate::{CalculatedSize, Node};
use bevy_asset::{Assets, Handle};
use bevy_ecs::{Changed, Entity, Local, Query, Res, ResMut};
use bevy_math::Size;
use bevy_render::{
    draw::{Draw, DrawContext, Drawable},
    prelude::Msaa,
    renderer::{AssetRenderResourceBindings, RenderResourceBindings},
    texture::Texture,
};
use bevy_sprite::TextureAtlas;
use bevy_text::{DrawableText, Font, FontAtlasSet, TextStyle};
use bevy_transform::prelude::GlobalTransform;

#[derive(Debug, Default)]
pub struct QueuedText {
    entities: Vec<Entity>,
}

#[derive(Debug, Default, Clone)]
pub struct Text {
    pub value: String,
    pub font: Handle<Font>,
    pub style: TextStyle,
}

pub fn text_system(
    mut queued_text: Local<QueuedText>,
    mut textures: ResMut<Assets<Texture>>,
    fonts: Res<Assets<Font>>,
    mut font_atlas_sets: ResMut<Assets<FontAtlasSet>>,
    mut texture_atlases: ResMut<Assets<TextureAtlas>>,
    mut query: Query<(Entity, Changed<Text>, &mut CalculatedSize)>,
    mut text_query: Query<(&Text, &mut CalculatedSize)>,
) {
    // add queued text to atlases
    let mut new_queued_text = Vec::new();
    for entity in queued_text.entities.drain(..) {
        if let Ok(mut result) = text_query.entity(entity) {
            if let Some((text, mut calculated_size)) = result.get() {
                let font_atlases = font_atlas_sets
                    .get_or_insert_with(text.font.id, || FontAtlasSet::new(text.font.clone_weak()));
                // TODO: this call results in one or more TextureAtlases, whose render resources are created in the RENDER_GRAPH_SYSTEMS
                // stage. That logic runs _before_ the DRAW stage, which means we cant call add_glyphs_to_atlas in the draw stage
                // without our render resources being a frame behind. Therefore glyph atlasing either needs its own system or the TextureAtlas
                // resource generation needs to happen AFTER the render graph systems. maybe draw systems should execute within the
                // render graph so ordering like this can be taken into account? Maybe the RENDER_GRAPH_SYSTEMS stage should be removed entirely
                // in favor of node.update()? Regardless, in the immediate short term the current approach is fine.
                if let Some(width) = font_atlases.add_glyphs_to_atlas(
                    &fonts,
                    &mut texture_atlases,
                    &mut textures,
                    text.style.font_size,
                    &text.value,
                ) {
                    calculated_size.size = Size::new(width, text.style.font_size);
                } else {
                    new_queued_text.push(entity);
                }
            }
        }
    }

    queued_text.entities = new_queued_text;

    // add changed text to atlases
    for (entity, text, mut calculated_size) in &mut query.iter() {
        let font_atlases = font_atlas_sets
            .get_or_insert_with(text.font.id, || FontAtlasSet::new(text.font.clone_weak()));
        // TODO: this call results in one or more TextureAtlases, whose render resources are created in the RENDER_GRAPH_SYSTEMS
        // stage. That logic runs _before_ the DRAW stage, which means we cant call add_glyphs_to_atlas in the draw stage
        // without our render resources being a frame behind. Therefore glyph atlasing either needs its own system or the TextureAtlas
        // resource generation needs to happen AFTER the render graph systems. maybe draw systems should execute within the
        // render graph so ordering like this can be taken into account? Maybe the RENDER_GRAPH_SYSTEMS stage should be removed entirely
        // in favor of node.update()? Regardless, in the immediate short term the current approach is fine.
        if let Some(width) = font_atlases.add_glyphs_to_atlas(
            &fonts,
            &mut texture_atlases,
            &mut textures,
            text.style.font_size,
            &text.value,
        ) {
            calculated_size.size = Size::new(width, text.style.font_size);
        } else {
            queued_text.entities.push(entity);
        }
    }
}

#[allow(clippy::too_many_arguments)]
pub fn draw_text_system(
    mut draw_context: DrawContext,
    fonts: Res<Assets<Font>>,
    msaa: Res<Msaa>,
    font_atlas_sets: Res<Assets<FontAtlasSet>>,
    texture_atlases: Res<Assets<TextureAtlas>>,
    mut render_resource_bindings: ResMut<RenderResourceBindings>,
    mut asset_render_resource_bindings: ResMut<AssetRenderResourceBindings>,
    mut query: Query<(&mut Draw, &Text, &Node, &GlobalTransform)>,
) {
    for (mut draw, text, node, global_transform) in &mut query.iter() {
        if let Some(font) = fonts.get(&text.font) {
            let position = global_transform.translation - (node.size / 2.0).extend(0.0);
            let mut drawable_text = DrawableText {
                font,
                font_atlas_set: font_atlas_sets.get(text.font.id).unwrap(),
                texture_atlases: &texture_atlases,
                render_resource_bindings: &mut render_resource_bindings,
                asset_render_resource_bindings: &mut asset_render_resource_bindings,
                position,
                msaa: &msaa,
                style: &text.style,
                text: &text.value,
                container_size: node.size,
            };
            drawable_text.draw(&mut draw, &mut draw_context).unwrap();
        }
    }
}