Add text wrapping support to Text2d (#4347)

# Objective

Fixes #4344.

## Solution

Add a new component `Text2dBounds` to `Text2dBundle` that specifies the maximum width and height of text. Text will wrap according to this size.

crates/bevy_text/src/text.rs

@@ -1,6 +1,5 @@
 use bevy_asset::Handle;
 use bevy_ecs::{prelude::Component, reflect::ReflectComponent};
-use bevy_math::Size;
 use bevy_reflect::{FromReflect, Reflect, ReflectDeserialize};
 use bevy_render::color::Color;
 use serde::{Deserialize, Serialize};
@@ -150,9 +149,3 @@ impl Default for TextStyle {
         }
     }
 }
-
-#[derive(Component, Default, Copy, Clone, Debug, Reflect)]
-#[reflect(Component)]
-pub struct Text2dSize {
-    pub size: Size,
-}

crates/bevy_text/src/text2d.rs

@@ -1,46 +1,63 @@
 use bevy_asset::Assets;
 use bevy_ecs::{
     bundle::Bundle,
+    component::Component,
     entity::Entity,
     query::{Changed, QueryState, With},
+    reflect::ReflectComponent,
     system::{Local, Query, QuerySet, Res, ResMut},
 };
 use bevy_math::{Size, Vec3};
+use bevy_reflect::Reflect;
 use bevy_render::{texture::Image, view::Visibility, RenderWorld};
 use bevy_sprite::{ExtractedSprite, ExtractedSprites, TextureAtlas};
 use bevy_transform::prelude::{GlobalTransform, Transform};
 use bevy_window::{WindowId, Windows};
 
 use crate::{
-    DefaultTextPipeline, Font, FontAtlasSet, HorizontalAlign, Text, Text2dSize, TextError,
-    VerticalAlign,
+    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: Size,
+}
+
+/// 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: Size,
+}
+
+impl Default for Text2dBounds {
+    fn default() -> Self {
+        Self {
+            size: Size::new(f32::MAX, f32::MAX),
+        }
+    }
+}
+
 /// The bundle of components needed to draw text in a 2D scene via a 2D `OrthographicCameraBundle`.
 /// [Example usage.](https://github.com/bevyengine/bevy/blob/latest/examples/2d/text2d.rs)
-#[derive(Bundle, Clone, Debug)]
+#[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,
 }
 
-impl Default for Text2dBundle {
-    fn default() -> Self {
-        Self {
-            text: Default::default(),
-            transform: Default::default(),
-            global_transform: Default::default(),
-            text_2d_size: Text2dSize {
-                size: Size::default(),
-            },
-            visibility: Default::default(),
-        }
-    }
-}
-
 pub fn extract_text2d_sprite(
     mut render_world: ResMut<RenderWorld>,
     texture_atlases: Res<Assets<TextureAtlas>>,
@@ -123,7 +140,7 @@ pub fn text2d_system(
     mut text_pipeline: ResMut<DefaultTextPipeline>,
     mut text_queries: QuerySet<(
         QueryState<Entity, (With<Text2dSize>, Changed<Text>)>,
-        QueryState<(&Text, &mut Text2dSize), With<Text2dSize>>,
+        QueryState<(&Text, Option<&Text2dBounds>, &mut Text2dSize), With<Text2dSize>>,
     )>,
 ) {
     // Adds all entities where the text or the style has changed to the local queue
@@ -141,14 +158,21 @@ pub fn text2d_system(
     let mut new_queue = Vec::new();
     let mut query = text_queries.q1();
     for entity in queued_text.entities.drain(..) {
-        if let Ok((text, mut calculated_size)) = query.get_mut(entity) {
+        if let Ok((text, bounds, mut calculated_size)) = query.get_mut(entity) {
+            let text_bounds = match bounds {
+                Some(bounds) => Size {
+                    width: scale_value(bounds.size.width, scale_factor),
+                    height: scale_value(bounds.size.height, scale_factor),
+                },
+                None => Size::new(f32::MAX, f32::MAX),
+            };
             match text_pipeline.queue_text(
                 entity,
                 &fonts,
                 &text.sections,
                 scale_factor,
                 text.alignment,
-                Size::new(f32::MAX, f32::MAX),
+                text_bounds,
                 &mut *font_atlas_set_storage,
                 &mut *texture_atlases,
                 &mut *textures,

examples/2d/text2d.rs

@@ -1,4 +1,4 @@
-use bevy::prelude::*;
+use bevy::{prelude::*, text::Text2dBounds};
 
 fn main() {
     App::new()
@@ -47,10 +47,46 @@ fn setup(mut commands: Commands, asset_server: Res<AssetServer>) {
     // Demonstrate changing scale
     commands
         .spawn_bundle(Text2dBundle {
-            text: Text::with_section("scale", text_style, text_alignment),
+            text: Text::with_section("scale", text_style.clone(), text_alignment),
             ..default()
         })
         .insert(AnimateScale);
+    // Demonstrate text wrapping
+    let box_size = Size::new(300.0, 200.0);
+    let box_position = Vec2::new(0.0, -250.0);
+    commands.spawn_bundle(SpriteBundle {
+        sprite: Sprite {
+            color: Color::rgb(0.25, 0.25, 0.75),
+            custom_size: Some(Vec2::new(box_size.width, box_size.height)),
+            ..default()
+        },
+        transform: Transform::from_translation(box_position.extend(0.0)),
+        ..default()
+    });
+    let text_alignment_topleft = TextAlignment {
+        vertical: VerticalAlign::Top,
+        horizontal: HorizontalAlign::Left,
+    };
+    commands.spawn_bundle(Text2dBundle {
+        text: Text::with_section(
+            "this text wraps in the box",
+            text_style,
+            text_alignment_topleft,
+        ),
+        text_2d_bounds: Text2dBounds {
+            // Wrap text in the rectangle
+            size: box_size,
+        },
+        // We align text to the top-left, so this transform is the top-left corner of our text. The
+        // box is centered at box_position, so it is necessary to move by half of the box size to
+        // keep the text in the box.
+        transform: Transform::from_xyz(
+            box_position.x - box_size.width / 2.0,
+            box_position.y + box_size.height / 2.0,
+            1.0,
+        ),
+        ..default()
+    });
 }
 
 fn animate_translation(