feature: Eliah shell — perspective-based IDE (one window, splitter-tree layout)

• Type: feature (epic / Track B)
• Status: done
• Closed 2026-06-29 (board cleanup): epic M1–M5 complete — layout-tree, perspectives, component-palette, selection-link all in done/. Only cosmetic strip polish deferred (not blocking). Shell scope delivered.
• Track: B
• Parent: feature-eliah-ide
• Opened: 2026-06-23

Vision

Eliah is one window. No floating palettes/inspectors/forms — that soup is the Delphi/Lazarus lesson we refuse to repeat. The window is a tree of splitters (nested TPaned); every visible thing (file tree, editor, console, form preview, object inspector, palette) is a leaf pane in that tree.

"Code editor", "GUI designer", and "Split" are not modes in the code — they are three saved layout descriptors (perspectives). Switching mode reflows the same panes; it never opens a window and never branches app logic.

The one rule (do not violate)

Mode = pure layout. The document workspace, project model, selection, and doc model are mode-independent. The moment if DesignMode then … leaks into logic, we have rebuilt Lazarus. A perspective only decides which panes are visible and how the splitter tree is arranged.

Principles (carried into every milestone)

• Splitter tree, not flat. Window = binary tree of H/V TPaned; leaves are pane containers. A perspective = serialized tree + ratios.
• Leaf = slot, not view. A leaf holds one view today, a tab strip later. Build the slot abstraction now so tabs are an upgrade, not a rewrite.
• Collapse ≠ destroy. Dragging/▾ a pane to its edge collapses it to a thin clickable strip that remembers its last ratio.
• Compacting is priority + min, not magic. Panes carry a min-size and a priority. Distribute by ratio, clamp to min; when the window can't satisfy the sum of mins, auto-collapse the lowest-priority pane. Predictable > pretty.
• Components are a registry. Visual widgets and non-visual libraries are the same thing: a registered TComponent with published RTTI. The palette lists RegisterClass'd components; non-visual ones live in a tray.
• Selection is a shared, bidirectional event. Designer↔editor link, and any future AI command, ride one selection/command model — never special layout.

Milestones — M1–M5 DONE (2026-06-24)

1. ✅ done/feature-eliah-layout-tree — window → nested-TPaned tree.
2. ✅ done/feature-eliah-pane-collapse (core) — full collapse/restore + View toggles. DEFERRED sub-item: the labelled clickable collapse strip + per-pane chevron (needed a stacking container; now UNBLOCKED — done/ bug-widgetset-virtual-arg-corruption cleared the TWidgetSet-virtual block, so the strip widget can be built).
3. ✅ done/feature-eliah-perspectives — Code/Design/Split presets + compacting.
4. ✅ done/feature-eliah-component-palette — registry palette (visual + non-visual tray) + RTTI inspector, on the TComponent/Create(AOwner) model.
5. ✅ done/feature-eliah-selection-link — shared bidirectional selection link (designer↔editor) + wire-OnClick command; the rail AI tooling will ride (backlog/feature-eliah-ai-command-rail).

All five milestones are complete; only the M2 collapse-strip/chevron polish is deferred (now unblocked). The shell is registry-driven with a shared selection/command surface.

Future (not yet ticketed)

• Tabs inside a leaf pane (the slot upgrade).
• AI tooling as a console pane + commands over the doc model ("link button click to …") — rides milestone 5's selection/command model, no layout special-case.

Related

• done/feature-eliah-pane-reflow (basic resize) is superseded by milestone 1.
• unfinished/feature-eliah-from-lfm (stream Eliah's own layout) and urgent/bug-metaclass-new-getclass-vmt are orthogonal but converge: once the shell is data-driven, the layout itself can be a streamed/serialized form.

Log

• 2026-06-23 — filed (epic) after the layout design discussion.