bevy/crates
ickshonpe 300fe4db4d
Store UI render target info locally per node (#17579)
# Objective

It's difficult to understand or make changes to the UI systems because
of how each system needs to individually track changes to scale factor,
windows and camera targets in local hashmaps, particularly for new
contributors. Any major change inevitably introduces new scale factor
bugs.

Instead of per-system resolution we can resolve the camera target info
for all UI nodes in a system at the start of `PostUpdate` and then store
it per-node in components that can be queried with change detection.

Fixes #17578
Fixes #15143

## Solution

Store the UI render target's data locally per node in a component that
is updated in `PostUpdate` before any other UI systems run.

This component can be then be queried with change detection so that UI
systems no longer need to have knowledge of cameras and windows and
don't require fragile custom change detection solutions using local
hashmaps.

## Showcase
Compare `measure_text_system` from main (which has a bug the causes it
to use the wrong scale factor when a node's camera target changes):
```
pub fn measure_text_system(
    mut scale_factors_buffer: Local<EntityHashMap<f32>>,
    mut last_scale_factors: Local<EntityHashMap<f32>>,
    fonts: Res<Assets<Font>>,
    camera_query: Query<(Entity, &Camera)>,
    default_ui_camera: DefaultUiCamera,
    ui_scale: Res<UiScale>,
    mut text_query: Query<
        (
            Entity,
            Ref<TextLayout>,
            &mut ContentSize,
            &mut TextNodeFlags,
            &mut ComputedTextBlock,
            Option<&UiTargetCamera>,
        ),
        With<Node>,
    >,
    mut text_reader: TextUiReader,
    mut text_pipeline: ResMut<TextPipeline>,
    mut font_system: ResMut<CosmicFontSystem>,
) {
    scale_factors_buffer.clear();

    let default_camera_entity = default_ui_camera.get();

    for (entity, block, content_size, text_flags, computed, maybe_camera) in &mut text_query {
        let Some(camera_entity) = maybe_camera
            .map(UiTargetCamera::entity)
            .or(default_camera_entity)
        else {
            continue;
        };
        let scale_factor = match scale_factors_buffer.entry(camera_entity) {
            Entry::Occupied(entry) => *entry.get(),
            Entry::Vacant(entry) => *entry.insert(
                camera_query
                    .get(camera_entity)
                    .ok()
                    .and_then(|(_, c)| c.target_scaling_factor())
                    .unwrap_or(1.0)
                    * ui_scale.0,
            ),
        };

        if last_scale_factors.get(&camera_entity) != Some(&scale_factor)
            || computed.needs_rerender()
            || text_flags.needs_measure_fn
            || content_size.is_added()
        {
            create_text_measure(
                entity,
                &fonts,
                scale_factor.into(),
                text_reader.iter(entity),
                block,
                &mut text_pipeline,
                content_size,
                text_flags,
                computed,
                &mut font_system,
            );
        }
    }
    core::mem::swap(&mut *last_scale_factors, &mut *scale_factors_buffer);
}
```

with `measure_text_system` from this PR (which always uses the correct
scale factor):
```
pub fn measure_text_system(
    fonts: Res<Assets<Font>>,
    mut text_query: Query<
        (
            Entity,
            Ref<TextLayout>,
            &mut ContentSize,
            &mut TextNodeFlags,
            &mut ComputedTextBlock,
            Ref<ComputedNodeTarget>,
        ),
        With<Node>,
    >,
    mut text_reader: TextUiReader,
    mut text_pipeline: ResMut<TextPipeline>,
    mut font_system: ResMut<CosmicFontSystem>,
) {
    for (entity, block, content_size, text_flags, computed, computed_target) in &mut text_query {
        // Note: the ComputedTextBlock::needs_rerender bool is cleared in create_text_measure().
        if computed_target.is_changed()
            || computed.needs_rerender()
            || text_flags.needs_measure_fn
            || content_size.is_added()
        {
            create_text_measure(
                entity,
                &fonts,
                computed_target.scale_factor.into(),
                text_reader.iter(entity),
                block,
                &mut text_pipeline,
                content_size,
                text_flags,
                computed,
                &mut font_system,
            );
        }
    }
}
```

## Testing

I removed an alarming number of tests from the `layout` module but they
were mostly to do with the deleted camera synchronisation logic. The
remaining tests should all pass now.

The most relevant examples are `multiple_windows` and `split_screen`,
the behaviour of both should be unchanged from main.

---------

Co-authored-by: UkoeHB <37489173+UkoeHB@users.noreply.github.com>
Co-authored-by: Alice Cecile <alice.i.cecile@gmail.com>
2025-02-10 07:27:58 +00:00
..
bevy_a11y Cleanup publish process (#17728) 2025-02-09 17:46:19 +00:00
bevy_animation Cleanup publish process (#17728) 2025-02-09 17:46:19 +00:00
bevy_app Harden proc macro path resolution and add integration tests. (#17330) 2025-02-09 19:45:45 +00:00
bevy_asset Harden proc macro path resolution and add integration tests. (#17330) 2025-02-09 19:45:45 +00:00
bevy_audio Cleanup publish process (#17728) 2025-02-09 17:46:19 +00:00
bevy_color Upgrade to wgpu v24 (#17542) 2025-02-09 19:40:53 +00:00
bevy_core_pipeline Upgrade to wgpu v24 (#17542) 2025-02-09 19:40:53 +00:00
bevy_derive Cleanup publish process (#17728) 2025-02-09 17:46:19 +00:00
bevy_dev_tools Cleanup publish process (#17728) 2025-02-09 17:46:19 +00:00
bevy_diagnostic Cleanup publish process (#17728) 2025-02-09 17:46:19 +00:00
bevy_dylib Cleanup publish process (#17728) 2025-02-09 17:46:19 +00:00
bevy_ecs Improved Spawn APIs and Bundle Effects (#17521) 2025-02-09 23:32:56 +00:00
bevy_encase_derive Harden proc macro path resolution and add integration tests. (#17330) 2025-02-09 19:45:45 +00:00
bevy_gilrs Cleanup publish process (#17728) 2025-02-09 17:46:19 +00:00
bevy_gizmos Harden proc macro path resolution and add integration tests. (#17330) 2025-02-09 19:45:45 +00:00
bevy_gltf Cleanup publish process (#17728) 2025-02-09 17:46:19 +00:00
bevy_image Upgrade to wgpu v24 (#17542) 2025-02-09 19:40:53 +00:00
bevy_input Cleanup publish process (#17728) 2025-02-09 17:46:19 +00:00
bevy_input_focus Cleanup publish process (#17728) 2025-02-09 17:46:19 +00:00
bevy_internal Upgrade to wgpu v24 (#17542) 2025-02-09 19:40:53 +00:00
bevy_log Cleanup publish process (#17728) 2025-02-09 17:46:19 +00:00
bevy_macro_utils Harden proc macro path resolution and add integration tests. (#17330) 2025-02-09 19:45:45 +00:00
bevy_math Cleanup publish process (#17728) 2025-02-09 17:46:19 +00:00
bevy_mesh Upgrade to wgpu v24 (#17542) 2025-02-09 19:40:53 +00:00
bevy_mikktspace Move #![warn(clippy::allow_attributes, clippy::allow_attributes_without_reason)] to the workspace Cargo.toml (#17374) 2025-01-15 01:14:58 +00:00
bevy_pbr Upgrade to wgpu v24 (#17542) 2025-02-09 19:40:53 +00:00
bevy_picking Cleanup publish process (#17728) 2025-02-09 17:46:19 +00:00
bevy_platform_support Cleanup publish process (#17728) 2025-02-09 17:46:19 +00:00
bevy_ptr Cleanup publish process (#17728) 2025-02-09 17:46:19 +00:00
bevy_reflect Harden proc macro path resolution and add integration tests. (#17330) 2025-02-09 19:45:45 +00:00
bevy_remote Cleanup publish process (#17728) 2025-02-09 17:46:19 +00:00
bevy_render Improved Spawn APIs and Bundle Effects (#17521) 2025-02-09 23:32:56 +00:00
bevy_scene Cleanup publish process (#17728) 2025-02-09 17:46:19 +00:00
bevy_sprite Upgrade to wgpu v24 (#17542) 2025-02-09 19:40:53 +00:00
bevy_state Harden proc macro path resolution and add integration tests. (#17330) 2025-02-09 19:45:45 +00:00
bevy_tasks Cleanup publish process (#17728) 2025-02-09 17:46:19 +00:00
bevy_text Cleanup publish process (#17728) 2025-02-09 17:46:19 +00:00
bevy_time Cleanup publish process (#17728) 2025-02-09 17:46:19 +00:00
bevy_transform Improved Spawn APIs and Bundle Effects (#17521) 2025-02-09 23:32:56 +00:00
bevy_ui Store UI render target info locally per node (#17579) 2025-02-10 07:27:58 +00:00
bevy_utils Cleanup publish process (#17728) 2025-02-09 17:46:19 +00:00
bevy_window Cleanup publish process (#17728) 2025-02-09 17:46:19 +00:00
bevy_winit Upgrade to wgpu v24 (#17542) 2025-02-09 19:40:53 +00:00