feature: PCL components adopt the Create(AOwner) virtual-constructor shape

• Type: feature (Track B — lib/pcl component model)
• Status: DONE 2026-06-24 (commit e71cb1c) — shape migrated + streamer adopts the metaclass virtual ctor; the four constructor-skip stopgaps are reverted.
• Opened: 2026-06-23

Unblocked 2026-06-23: the compiler half is DONE (done/feature-metaclass-construct-dispatch, pinned v44). classRefVar.Create(args) dispatches through the dynamic VMT, parametrised virtual ctors work, and the TBaseClass(GetClass(name)).Create(AOwner) bridge is verified. PCL can now adopt the Create(AOwner); virtual; shape and have the streamer construct via metaclass.

Goal

Shape PCL's component/control classes like FPC's so the same source could compile under both and so the streamer constructs them through a metaclass:

• a virtual constructor Create(AOwner: TComponent); virtual; on the component base (currently PCL uses a parameterless constructor Create;),
• a minimal Owner/Components linkage so streamed objects have an owner.

This is the library half of urgent/feature-metaclass-construct-dispatch (the language half). They meet at "streaming constructs a component with an owner".

Ownership stance (deliberate)

FPC's TComponent auto-frees its owned children. We support the shape for compatibility but do NOT impose the religion:

• Owner = nil is first-class. In-app usage may pass nil and just set Parent — exactly as much FPC code already does. Manual free stays valid.
• Keep the Owner/Components list minimal (enough for streaming + FPC source to compile + optional cascade-free), not a mandatory lifecycle.

Rationale: the owner system solves some problems and creates others (nil-owner + parent-only is a common, cleaner app pattern). Compatibility ≠ enforcement.

Scope

• TComponent.Create(AOwner: TComponent); virtual; + Owner/Components (insert on create, optional cascade free on destroy).
• Migrate TControl/widgets to call inherited Create(AOwner) and stop relying on the parameterless form (keep a parameterless convenience if useful).
• Once metaclass-construct-dispatch lands: the streamer calls classRef.Create(owner); REVERT the constructor-skip stopgaps (done/bug-lfm-streaming-skips-constructors) — Canvas back in TPaintBox.Create, arrays back in TListBox/TComboBox.Create, drop the CreateInstance contract note.

Acceptance

A streamed widget tree is constructed via Create(AOwner) (Owner may be nil), widgets keep their natural constructors (no CreateHandle/lazy stopgaps), Eliah + gui_suite green. App code that passes nil owner + sets Parent works unchanged.

Note

Blocked-by urgent/feature-metaclass-construct-dispatch for the streaming path, but the Create(AOwner) migration itself can proceed independently.

Progress 2026-06-23

DONE (the migration, which the ticket says can proceed independently):

• classes_lite.TComponent.Create → constructor Create(AOwner: TComponent); virtual; + FOwner/Owner + TComponentClass = class of TComponent.
• All PCL widgets migrated to Create(AOwner); override; calling inherited Create(AOwner): controls.TControl, stdctrls (7), extctrls (TPanel/TTimer/TPaintBox/TPaned), menus (TMenuItem/TMenu), forms.TForm, glarea.TGLArea. graphics.* and TApplication stay parameterless (not components).
• All widget .Create call sites across apps/examples/test/gui pass an owner (nil — owner-less + Parent is first-class here). Form subclasses with their own ctor (TMainForm) became Create(AOwner); override;.
• gui_suite green (incl. streaming tests, paned, eliah), garin 92/92, eliah builds + smoke + screenshot.

BLOCKED — streamer adoption: replacing CreateInstance with TComponentClass(childCls).Create(parent) and dropping the four constructor-skip stopgaps. The metaclass-construct bridge stamps a non-canonical VMT → urgent/bug-metaclass-new-getclass-vmt. Streamer stays on CreateInstance + stopgaps (markers point at that ticket) until it lands.

Compiler gaps also hit (clean single-ctor path used instead, no workaround): default param on a constructor and overloaded constructors + inherited both fail to parse — noted for a future backlog ticket if the parameterless-convenience shape is ever wanted.

Progress 2026-06-24 — streamer adoption DONE

done/bug-metaclass-new-getclass-vmt (v45) cleared the block. TReader.ReadChildren now constructs each child via TComponentClass(childCls).Create(parent) (Owner = parent), so streamed components run their real virtual ctors. All four constructor-skip stopgaps reverted:

• TPaintBox.CreateHandle FCanvas=nil guard removed (ctor sets Canvas);
• TListBox/TComboBox FItems grow-on-demand kept only as plain robustness past the ctor's initial 256 reservation (stopgap rationale comment dropped);
• typinfo.CreateInstance STOPGAP CONTRACT note rewritten — the raw allocator now serves only the root-form load path (TApplication.CreateForm) + RTTI tests that deliberately skip the ctor.

Gates: garin 116/116, gui_suite OK (incl test_pcl_lfm streaming), eliah build+smoke+screenshot green. Commit e71cb1c.