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ComponentIndex

property ComponentIndex: Integer read write;

Example​

procedure MoveOwnedComponentFirst(const Item: TComponent);
begin
  if Item.Owner <> nil then
    Item.ComponentIndex := 0;
end;

Usage​

ComponentIndex reads or reorders a component's zero-based position within its owner's immediate component list.

Parameters and result

Read/write Integer. The getter can return -1; setter requests are clamped rather than rejected when the component is currently owned.

Behaviour

  • Reordering shifts other components' indexes.
  • Writing any value on an unowned component has no effect.
  • The property is positional and unstable across other owner-list mutations.
  • Order can affect Velox streaming/enumeration even though it is not a Velox business priority field.

Errors and edge cases

A nil receiver fails. For a normally owned component out-of-range writes are clamped; item/owner corruption or concurrent mutation can still surface list errors.

Additional Technical Info​

ComponentIndex is a script-visible property declared on hidden ancestor TComponent. Visible descendant classes inherit it even though Classes/Common is intentionally omitted from the Velox and Docusaurus Code Library menus.

ComponentIndex is the receiver's position in its owner's component list. Writing it changes enumeration/streaming order; it does not change the owner.

Implementation trace

Studio 37.0 returns the owner's list index or -1 without an owner/list. The setter does nothing without an owner, clamps negative values to 0 and values at/above count to count - 1, then deletes/inserts the reference when the target differs.

Side effects and ownership

A successful write mutates the owner's live list but does not free, adopt or rename a component.

Performance and concurrency

Getter is O(n) because it searches for the receiver; moving can be O(n). No concurrency guarantee.

Remarks

This entry describes the installed Delphi Studio 37.0 terminal reached by the Velox-modified PascalScript registration. Free Pascal is linked for compatible Object Pascal context; where implementations differ, the traced Delphi behaviour above is authoritative. The example is source-reviewed and non-destructive except where the named operation is inherently destructive.

Related entries

External references

Created 2026-07-15