Module layout_props 

Layout property types: Insets, HAnchor, VAnchor, WidgetBase.

These types mirror the C# agg-sharp BorderDouble, HAnchor, VAnchor, and the per-widget layout fields that every GuiWidget carried.

Design

Every concrete widget embeds a WidgetBase and delegates the five layout-property getters on the Widget trait to it. The parent layout container reads those getters when placing children.

All values are stored in logical (device-independent) units. WidgetBase::scaled_margin multiplies by the global device_scale factor to produce physical pixel values for use inside layout algorithms.

Margin vs padding

• Margin lives on the child and is read by the parent during layout. It is space outside the widget’s bounds.
• Padding is the parent container’s internal inset — space between its own border and its children. Containers store padding directly (e.g. FlexColumn::inner_padding); individual leaf widgets do not have padding.

Margin semantics

Margins are additive, not collapsed. When child A has margin.bottom = 4 and child B has margin.top = 6, the gap between them is gap + 4 + 6 = 10 + gap, not max(4, 6) = 6. This matches the original C# agg-sharp behaviour.

Structs

HAnchor

Horizontal anchor flags — how a widget sizes and positions itself horizontally within the slot assigned by its parent.

Insets

Per-side inset values (logical units).

VAnchor

Vertical anchor flags — how a widget sizes and positions itself vertically within the slot assigned by its parent.

WidgetBase

Stores the five universal layout properties that every widget carries.

Functions

resolve_fit_or_stretch

Given a natural (fit) size and a stretch (fill) size for one axis, resolve the MIN_FIT_OR_STRETCH or MAX_FIT_OR_STRETCH anchor to a concrete size.