Feature-gate all references to bevy_text in bevy_ui (#11391)

# Objective

- `bevy_ui` fails to compile without `bevy_text` being enabled.
- Fixes #11363.

## Solution

- Add `#[cfg(feature = "bevy_text")]` to all items that require it.

I think this change is honestly a bit ugly, but I can't see any other
way around it. I considered making `bevy_text` required, but we agreed
[on
Discord](https://discord.com/channels/691052431525675048/743663673393938453/1196868117486379148)
that there were some use cases for `bevy_ui` without `bevy_text`. If you
have any ideas that decreases the amount of `#[cfg(...)]`s and
`#[allow(...)]`s, that would be greatly appreciated.

This was tested by running the following commands:

```shell
$ cargo clippy -p bevy_ui
$ cargo clippy -p bevy_ui -F bevy_text
$ cargo run -p ci
```

---

## Changelog

- Fixed `bevy_ui` not compiling without `bevy_text`.

crates/bevy_ui/src/lib.rs

@@ -12,8 +12,6 @@ pub mod widget;
 use bevy_derive::{Deref, DerefMut};
 use bevy_reflect::Reflect;
 #[cfg(feature = "bevy_text")]
-use bevy_text::TextLayoutInfo;
-#[cfg(feature = "bevy_text")]
 mod accessibility;
 mod focus;
 mod geometry;
@@ -40,8 +38,6 @@ pub mod prelude {
     };
 }
 
-#[cfg(feature = "bevy_text")]
-use crate::widget::TextFlags;
 use bevy_app::prelude::*;
 use bevy_ecs::prelude::*;
 use bevy_input::InputSystem;
@@ -81,6 +77,14 @@ impl Default for UiScale {
     }
 }
 
+// Marks systems that can be ambiguous with [`widget::text_system`] if the `bevy_text` feature is enabled.
+// See https://github.com/bevyengine/bevy/pull/11391 for more details.
+#[derive(SystemSet, Debug, Hash, PartialEq, Eq, Clone)]
+struct AmbiguousWithTextSystem;
+
+#[derive(SystemSet, Debug, Hash, PartialEq, Eq, Clone)]
+struct AmbiguousWithUpdateText2DLayout;
+
 impl Plugin for UiPlugin {
     fn build(&self, app: &mut App) {
         app.init_resource::<UiSurface>()
@@ -129,51 +133,6 @@ impl Plugin for UiPlugin {
                 ui_focus_system.in_set(UiSystem::Focus).after(InputSystem),
             );
 
-        #[cfg(feature = "bevy_text")]
-        app.register_type::<TextLayoutInfo>()
-            .register_type::<TextFlags>();
-        // add these systems to front because these must run before transform update systems
-        #[cfg(feature = "bevy_text")]
-        app.add_systems(
-            PostUpdate,
-            (
-                widget::measure_text_system
-                    .before(UiSystem::Layout)
-                    // Potential conflict: `Assets<Image>`
-                    // In practice, they run independently since `bevy_render::camera_update_system`
-                    // will only ever observe its own render target, and `widget::measure_text_system`
-                    // will never modify a pre-existing `Image` asset.
-                    .ambiguous_with(bevy_render::camera::CameraUpdateSystem)
-                    // Potential conflict: `Assets<Image>`
-                    // Since both systems will only ever insert new [`Image`] assets,
-                    // they will never observe each other's effects.
-                    .ambiguous_with(bevy_text::update_text2d_layout)
-                    // We assume Text is on disjoint UI entities to UiImage and UiTextureAtlasImage
-                    // FIXME: Add an archetype invariant for this https://github.com/bevyengine/bevy/issues/1481.
-                    .ambiguous_with(widget::update_image_content_size_system),
-                widget::text_system
-                    .after(UiSystem::Layout)
-                    .after(bevy_text::remove_dropped_font_atlas_sets)
-                    // Text2d and bevy_ui text are entirely on separate entities
-                    .ambiguous_with(bevy_text::update_text2d_layout),
-            ),
-        );
-        #[cfg(feature = "bevy_text")]
-        app.add_plugins(accessibility::AccessibilityPlugin);
-        app.add_systems(PostUpdate, {
-            let system = widget::update_image_content_size_system.before(UiSystem::Layout);
-            // Potential conflicts: `Assets<Image>`
-            // They run independently since `widget::image_node_system` will only ever observe
-            // its own UiImage, and `widget::text_system` & `bevy_text::update_text2d_layout`
-            // will never modify a pre-existing `Image` asset.
-            #[cfg(feature = "bevy_text")]
-            let system = system
-                .ambiguous_with(bevy_text::update_text2d_layout)
-                .ambiguous_with(widget::text_system);
-
-            system
-        });
-
         app.add_systems(
             PostUpdate,
             (
@@ -189,18 +148,29 @@ impl Plugin for UiPlugin {
                     .after(UiSystem::Layout)
                     // clipping doesn't care about outlines
                     .ambiguous_with(update_clipping_system)
-                    .ambiguous_with(widget::text_system),
+                    .in_set(AmbiguousWithTextSystem),
                 ui_stack_system
                     .in_set(UiSystem::Stack)
                     // the systems don't care about stack index
                     .ambiguous_with(update_clipping_system)
                     .ambiguous_with(resolve_outlines_system)
                     .ambiguous_with(ui_layout_system)
-                    .ambiguous_with(widget::text_system),
+                    .in_set(AmbiguousWithTextSystem),
                 update_clipping_system.after(TransformSystem::TransformPropagate),
+                // Potential conflicts: `Assets<Image>`
+                // They run independently since `widget::image_node_system` will only ever observe
+                // its own UiImage, and `widget::text_system` & `bevy_text::update_text2d_layout`
+                // will never modify a pre-existing `Image` asset.
+                widget::update_image_content_size_system
+                    .before(UiSystem::Layout)
+                    .in_set(AmbiguousWithTextSystem)
+                    .in_set(AmbiguousWithUpdateText2DLayout),
             ),
         );
 
+        #[cfg(feature = "bevy_text")]
+        build_text_interop(app);
+
         build_ui_render(app);
     }
 
@@ -212,3 +182,50 @@ impl Plugin for UiPlugin {
         render_app.init_resource::<UiPipeline>();
     }
 }
+
+/// A function that should be called from [`UiPlugin::build`] when [`bevy_text`] is enabled.
+#[cfg(feature = "bevy_text")]
+fn build_text_interop(app: &mut App) {
+    use crate::widget::TextFlags;
+    use bevy_text::TextLayoutInfo;
+
+    app.register_type::<TextLayoutInfo>()
+        .register_type::<TextFlags>();
+
+    app.add_systems(
+        PostUpdate,
+        (
+            widget::measure_text_system
+                .before(UiSystem::Layout)
+                // Potential conflict: `Assets<Image>`
+                // In practice, they run independently since `bevy_render::camera_update_system`
+                // will only ever observe its own render target, and `widget::measure_text_system`
+                // will never modify a pre-existing `Image` asset.
+                .ambiguous_with(bevy_render::camera::CameraUpdateSystem)
+                // Potential conflict: `Assets<Image>`
+                // Since both systems will only ever insert new [`Image`] assets,
+                // they will never observe each other's effects.
+                .ambiguous_with(bevy_text::update_text2d_layout)
+                // We assume Text is on disjoint UI entities to UiImage and UiTextureAtlasImage
+                // FIXME: Add an archetype invariant for this https://github.com/bevyengine/bevy/issues/1481.
+                .ambiguous_with(widget::update_image_content_size_system),
+            widget::text_system
+                .after(UiSystem::Layout)
+                .after(bevy_text::remove_dropped_font_atlas_sets)
+                // Text2d and bevy_ui text are entirely on separate entities
+                .ambiguous_with(bevy_text::update_text2d_layout),
+        ),
+    );
+
+    app.add_plugins(accessibility::AccessibilityPlugin);
+
+    app.configure_sets(
+        PostUpdate,
+        AmbiguousWithTextSystem.ambiguous_with(widget::text_system),
+    );
+
+    app.configure_sets(
+        PostUpdate,
+        AmbiguousWithUpdateText2DLayout.ambiguous_with(bevy_text::update_text2d_layout),
+    );
+}

crates/bevy_ui/src/render/mod.rs

@@ -14,9 +14,9 @@ pub use render_pass::*;
 pub use ui_material_pipeline::*;
 
 use crate::{
-    BackgroundColor, BorderColor, CalculatedClip, ContentSize, Node, Style, UiImage, UiScale, Val,
+    BackgroundColor, BorderColor, CalculatedClip, ContentSize, DefaultUiCamera, Node, Outline,
+    Style, TargetCamera, UiImage, UiScale, Val,
 };
-use crate::{DefaultUiCamera, Outline, TargetCamera};
 
 use bevy_app::prelude::*;
 use bevy_asset::{load_internal_asset, AssetEvent, AssetId, Assets, Handle};
@@ -34,7 +34,6 @@ use bevy_render::{
     view::{ExtractedView, ViewUniforms},
     Extract, RenderApp, RenderSet,
 };
-#[cfg(feature = "bevy_text")]
 use bevy_sprite::TextureAtlasLayout;
 #[cfg(feature = "bevy_text")]
 use bevy_text::{PositionedGlyph, Text, TextLayoutInfo};

crates/bevy_ui/src/widget/image.rs

@@ -1,14 +1,6 @@
 use crate::{measurement::AvailableSpace, ContentSize, Measure, Node, UiImage, UiScale};
 use bevy_asset::Assets;
-
+use bevy_ecs::prelude::*;
-use bevy_ecs::change_detection::DetectChanges;
-use bevy_ecs::query::Without;
-use bevy_ecs::{
-    prelude::Component,
-    query::With,
-    reflect::ReflectComponent,
-    system::{Local, Query, Res},
-};
 use bevy_math::Vec2;
 use bevy_reflect::{std_traits::ReflectDefault, Reflect};
 use bevy_render::texture::Image;