bevy/crates/bevy_text/src/text2d.rs

use bevy_asset::Assets;
use bevy_ecs::{
    bundle::Bundle,
    component::Component,
    entity::Entity,
    event::EventReader,
    query::Changed,
    reflect::ReflectComponent,
    system::{Local, Query, Res, ResMut},
};
use bevy_math::{Vec2, Vec3};
use bevy_reflect::Reflect;
use bevy_render::{texture::Image, view::Visibility, Extract};
use bevy_sprite::{Anchor, ExtractedSprite, ExtractedSprites, TextureAtlas};
use bevy_transform::prelude::{GlobalTransform, Transform};
use bevy_utils::HashSet;
use bevy_window::{WindowId, WindowScaleFactorChanged, Windows};

use crate::{
    DefaultTextPipeline, Font, FontAtlasSet, HorizontalAlign, Text, TextError, VerticalAlign,
};

/// The calculated size of text drawn in 2D scene.
#[derive(Component, Default, Copy, Clone, Debug, Reflect)]
#[reflect(Component)]
pub struct Text2dSize {
    pub size: Vec2,
}

/// The maximum width and height of text. The text will wrap according to the specified size.
/// Characters out of the bounds after wrapping will be truncated. Text is aligned according to the
/// specified `TextAlignment`.
///
/// Note: only characters that are completely out of the bounds will be truncated, so this is not a
/// reliable limit if it is necessary to contain the text strictly in the bounds. Currently this
/// component is mainly useful for text wrapping only.
#[derive(Component, Copy, Clone, Debug, Reflect)]
#[reflect(Component)]
pub struct Text2dBounds {
    pub size: Vec2,
}

impl Default for Text2dBounds {
    fn default() -> Self {
        Self {
            size: Vec2::new(f32::MAX, f32::MAX),
        }
    }
}

/// The bundle of components needed to draw text in a 2D scene via a 2D `Camera2dBundle`.
/// [Example usage.](https://github.com/bevyengine/bevy/blob/latest/examples/2d/text2d.rs)
#[derive(Bundle, Clone, Debug, Default)]
pub struct Text2dBundle {
    pub text: Text,
    pub transform: Transform,
    pub global_transform: GlobalTransform,
    pub text_2d_size: Text2dSize,
    pub text_2d_bounds: Text2dBounds,
    pub visibility: Visibility,
}

pub fn extract_text2d_sprite(
    mut extracted_sprites: ResMut<ExtractedSprites>,
    texture_atlases: Extract<Res<Assets<TextureAtlas>>>,
    text_pipeline: Extract<Res<DefaultTextPipeline>>,
    windows: Extract<Res<Windows>>,
    text2d_query: Extract<Query<(Entity, &Visibility, &Text, &GlobalTransform, &Text2dSize)>>,
) {
    let scale_factor = windows.scale_factor(WindowId::primary()) as f32;
    for (entity, visibility, text, transform, calculated_size) in text2d_query.iter() {
        if !visibility.is_visible {
            continue;
        }
        let (width, height) = (calculated_size.size.x, calculated_size.size.y);

        if let Some(text_layout) = text_pipeline.get_glyphs(&entity) {
            let text_glyphs = &text_layout.glyphs;
            let alignment_offset = match text.alignment.vertical {
                VerticalAlign::Top => Vec3::new(0.0, -height, 0.0),
                VerticalAlign::Center => Vec3::new(0.0, -height * 0.5, 0.0),
                VerticalAlign::Bottom => Vec3::ZERO,
            } + match text.alignment.horizontal {
                HorizontalAlign::Left => Vec3::ZERO,
                HorizontalAlign::Center => Vec3::new(-width * 0.5, 0.0, 0.0),
                HorizontalAlign::Right => Vec3::new(-width, 0.0, 0.0),
            };

            let mut text_transform = *transform;
            text_transform.scale /= scale_factor;

            for text_glyph in text_glyphs {
                let color = text.sections[text_glyph.section_index]
                    .style
                    .color
                    .as_rgba_linear();
                let atlas = texture_atlases
                    .get(&text_glyph.atlas_info.texture_atlas)
                    .unwrap();
                let handle = atlas.texture.clone_weak();
                let index = text_glyph.atlas_info.glyph_index as usize;
                let rect = Some(atlas.textures[index]);

                let glyph_transform = Transform::from_translation(
                    alignment_offset * scale_factor + text_glyph.position.extend(0.),
                );

                let transform = text_transform.mul_transform(glyph_transform);

                extracted_sprites.sprites.push(ExtractedSprite {
                    transform,
                    color,
                    rect,
                    custom_size: None,
                    image_handle_id: handle.id,
                    flip_x: false,
                    flip_y: false,
                    anchor: Anchor::Center.as_vec(),
                });
            }
        }
    }
}

/// Updates the layout and size information whenever the text or style is changed.
/// This information is computed by the `TextPipeline` on insertion, then stored.
#[allow(clippy::too_many_arguments)]
pub fn update_text2d_layout(
    // Text items which should be reprocessed again, generally when the font hasn't loaded yet.
    mut queue: Local<HashSet<Entity>>,
    mut textures: ResMut<Assets<Image>>,
    fonts: Res<Assets<Font>>,
    windows: Res<Windows>,
    mut scale_factor_changed: EventReader<WindowScaleFactorChanged>,
    mut texture_atlases: ResMut<Assets<TextureAtlas>>,
    mut font_atlas_set_storage: ResMut<Assets<FontAtlasSet>>,
    mut text_pipeline: ResMut<DefaultTextPipeline>,
    mut text_query: Query<(
        Entity,
        Changed<Text>,
        &Text,
        Option<&Text2dBounds>,
        &mut Text2dSize,
    )>,
) {
    // We need to consume the entire iterator, hence `last`
    let factor_changed = scale_factor_changed.iter().last().is_some();
    let scale_factor = windows.scale_factor(WindowId::primary());

    for (entity, text_changed, text, maybe_bounds, mut calculated_size) in text_query.iter_mut() {
        if factor_changed || text_changed || queue.remove(&entity) {
            let text_bounds = match maybe_bounds {
                Some(bounds) => Vec2::new(
                    scale_value(bounds.size.x, scale_factor),
                    scale_value(bounds.size.y, scale_factor),
                ),
                None => Vec2::new(f32::MAX, f32::MAX),
            };
            match text_pipeline.queue_text(
                entity,
                &fonts,
                &text.sections,
                scale_factor,
                text.alignment,
                text_bounds,
                &mut *font_atlas_set_storage,
                &mut *texture_atlases,
                &mut *textures,
            ) {
                Err(TextError::NoSuchFont) => {
                    // There was an error processing the text layout, let's add this entity to the
                    // queue for further processing
                    queue.insert(entity);
                }
                Err(e @ TextError::FailedToAddGlyph(_)) => {
                    panic!("Fatal error when processing text: {}.", e);
                }
                Ok(()) => {
                    let text_layout_info = text_pipeline.get_glyphs(&entity).expect(
                        "Failed to get glyphs from the pipeline that have just been computed",
                    );
                    calculated_size.size = Vec2::new(
                        scale_value(text_layout_info.size.x, 1. / scale_factor),
                        scale_value(text_layout_info.size.y, 1. / scale_factor),
                    );
                }
            }
        }
    }
}

pub fn scale_value(value: f32, factor: f64) -> f32 {
    (value as f64 * factor) as f32
}