Fix debug-profile slider stutter (#25500) - #25536
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EditableText re-triggered intrinsic-size recomputation and a full Taffy layout pass every frame regardless of whether its rendered size had actually changed, and ColorSlider/ColorPlane moved their thumb via Node::left/top (layout-affecting properties), forcing a relayout on every frame during drag. In debug builds this made the color slider/plane update in visible discrete steps instead of smoothly. - Cache the inputs that determine EditableText's intrinsic size (visible_width/visible_lines) and only recompute when they change. - Move ColorSlider and ColorPlane thumb positioning to UiTransform, which doesn't invalidate layout, instead of Node::left/top. - Split ColorPlane's thumb positioning into its own unfiltered system so it keeps tracking the container's resized size every frame, while update_plane_color keeps its Changed filter to avoid needlessly mutating Assets<ColorPlaneMaterial>. Debug-profile FPS during continuous slider drag went from ~11-14 FPS to ~59-63 FPS on Linux + NVIDIA RTX 4070 + Vulkan.
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The macOS build job did not report a test failure; it was cancelled after reaching the workflow’s 40-minute timeout while running cargo run -p ci -- test. Ubuntu and Windows builds passed, as did run-examples-macos-metal. I’ll update the branch against current main to trigger a fresh run. If macOS times out again, could a maintainer please rerun the failed job? |
…sue-25500-slider-debug-perf # Conflicts: # crates/bevy_feathers/src/controls/color_slider.rs
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Objective
feathers_gallerypoor performance in debug mode #25500.feathers_galleryupdated in visible discrete steps instead of smoothly. Measured on Linux + NVIDIA RTX 4070 + Vulkan: out of 138 consecutive frames during a slow, controlled drag, only 86 states were unique (52 frames repeated the previous state) in debug, versus 129/138 unique in release. The slider's value updated correctly the whole time — this was a rendering smoothness problem, not an input problem.EditableTexttriggered a full intrinsic-size recomputation (and thus a full Taffy layout pass) every frame, regardless of whether its rendered size had actually changed.ColorSliderandColorPlanemoved their thumb every frame by writingNode::left/Node::top, which are layout-affecting properties and force a Taffy relayout on every frame during a drag.Solution
update_editable_text_content_sizenow caches the inputs that actually determineEditableText's intrinsic size (visible_width,visible_lines) in a newEditableTextContentSizeStatecomponent, and only recomputes when those specific fields change, instead of on every change toEditableText(which also churns from unrelated fields like cursor blink/edits).EditableTextContentSizeStateis wired up as a required component ofbevy_text::EditableTextviaregister_required_componentsinUiPlugin, sincebevy_textdoesn't depend onbevy_ui.ColorSliderandColorPlanenow position their thumb viaUiTransforminstead ofNode::left/Node::top.UiTransformis applied after layout and doesn't invalidate Taffy, so moving the thumb no longer forces a relayout.ColorPlane's thumb positioning was split out ofupdate_plane_colorinto its own system,update_plane_thumb_position, which runs unconditionally every frame so the thumb keeps tracking the parent node's actual size (e.g. on window resize) even when the color value hasn't changed.update_plane_colorkeeps its originalChangedfilter, since it mutatesAssets<ColorPlaneMaterial>, which is comparatively expensive to touch every frame.Testing
cargo test -p bevy_ui --lib: 66/66 passed.cargo test -p bevy_feathers --lib: 10/10 passed.cargo fmt --checkandgit diff --checkpass.feathers_gallery(debug profile) that the color slider and color plane thumbs track the mouse correctly and land at the right position during and after a drag.