Panel

Layer: organism · Path: src/organisms/panel.rs · Exports: panel::{Panel, PanelEdge}

A canonical docked panel: a background, an optional flush hairline on its docking edge, an optional header (title + action slot) and footer action bar, and a scrollable, token-padded body. Mounts inside a rect — typically a Splitter band via a child Ui. Unlike the elevated, rounded Card, a Panel is flush (no radius, no shadow) with a single edge border — the studio inspector / properties chrome, so panels stop hand-rolling egui::Frame margins and manually painted borders/headers.

Design

Purpose / when to use — Any docked side panel / inspector / properties pane. For a free-floating elevated container use Card; for the resizable bands themselves use Splitter (a Panel goes inside a band).
Anatomy — background Surface filling the mounted rect → optional flush edge Divider carved off the docking side → optional header (Heading + right-aligned action, then a full-width divider) → padded, scrollable body → optional footer (full-width divider + action bar pinned to the bottom).

Variants / states

Axis	Options
`edge` (`PanelEdge`)	`None` (default) · `Left` · `Right` · `Top` · `Bottom`
`fill` (`SurfaceFill`)	`Background` (default) · `Card` · `Muted` · `None` (module paints its own bg)
`scroll`	on (default) · `.no_scroll()`
header / footer	absent unless `.title()`/`.action()` / `.footer()` set

Tokens / layout consumed — layout::PANEL_PAD (body/header/footer inset), layout::PANEL_GAP (row gap), core::BORDER_THIN (edge weight), the chosen SurfaceFill token.
Layering — organism: composes Surface, Divider, Heading; never paints directly (the no_painter_in_molecules guard scans organisms too).
Accessibility — scrolling/keyboard come from egui’s ScrollArea; the body width is pinned so fill controls don’t ratchet (egui #1297).

API

Signature	Effect
`Panel::new(id: impl Hash) -> Self`	New panel; `id` keys the body `ScrollArea`.
`.title(title: impl Into<String>) -> Self`	Header title (a `Heading`) above a full-width divider.
`.action(f: impl FnOnce(&mut Ui) + 'a) -> Self`	Top-right header slot (button / menu / badge).
`.footer(f: impl FnOnce(&mut Ui) + 'a) -> Self`	Bottom action bar above a full-width divider.
`.edge(e: PanelEdge) -> Self` / `.left_edge()` / `.right_edge()`	Flush hairline on the docking edge.
`.fill(f: SurfaceFill) -> Self`	Background fill (default `Background`).
`.no_scroll() -> Self`	Don’t wrap the body in a `ScrollArea`.
`.body_pad(px: f32) -> Self`	Body inner padding (default `PANEL_PAD`); `0.0` = flush for content that manages its own insets (e.g. full-bleed accordion section headers).
`.show(self, ui: &mut Ui, content: impl FnOnce(&mut Ui)) -> Response`	Paint the chrome; run `content` in the padded body.

Usage

#![allow(unused)]
fn main() {
use ouroboros_ui::organisms::Panel;
use ouroboros_ui::cells::ResponsiveRow;
use ouroboros_ui::atoms::NumericField;

// Right-docked inspector mounted in a Splitter band rect (a child Ui).
Panel::new("world_inspector")
    .left_edge()
    .title("Inspector")
    .show(ui, |ui| {
        ResponsiveRow::new("Mass").show(ui, |ui| {
            NumericField::new(&mut mass).speed(0.05).show(ui)
        });
    });
}

Composition

Carves the edge hairline off ui.max_rect() with Rect::split_*_at_*, draws a Divider in the strip, and stacks header / scrollable body / footer in the remainder via child Uis. The body is a port of the studio’s panel_body helper: ScrollArea::vertical().auto_shrink([true, false]) + a Surface (no fill) padded by PANEL_PAD, with the content width pinned via set_min_width and a PANEL_GAP row spacing. A footer is laid bottom-up so it pins to the panel’s bottom edge.

Notes

The body keeps horizontal auto-shrink on (egui #1297): a fill control inside a scroll area with horizontal auto-shrink off ratchets the content width on resize. Don’t change this.
fill(SurfaceFill::None) leaves the background to the host module (the legacy studio pattern) while still giving the canonical edge/header/body chrome.
Replaces hand-rolled studio panel chrome: per-section Frame::inner_margin, manual line_segment/rect_filled edges, and hand-painted section headers.

See tokens · theming · guards.

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Panel

Design

API

Usage

Composition

Notes