Getter Migration Plan: CssPropertyCache → Centralized Getters

Goal

Route ALL CSS property access through layout/src/solver3/getters.rs.
This allows us to later replace the BTreeMap-based CssPropertyCache with an
FxHashMap-based system that uses the 3-tier compact cache as the primary path.

After migration, CssPropertyCache.get_*() methods should ONLY be called from:

getters.rs (as the slow-path fallback)
compact_cache_builder.rs (to build the compact cache once)
core/src/prop_cache.rs internal helper methods
core/src/styled_dom.rs for generic property access (devtools, animation)

Current State

Properties WITH compact cache fast path (already migrated)

Tier 1 — Bitpacked enums (21 properties):

display, position, float, overflow_x, overflow_y, box_sizing
flex_direction, flex_wrap, justify_content, align_items, align_content
writing_mode, clear, font_weight, font_style, text_align
visibility, white_space, direction, vertical_align, border_collapse

Tier 2 — CompactNodeProps (96 bytes/node):

width, height, min_width, max_width, min_height, max_height, flex_basis, font_size
padding_top/right/bottom/left, margin_top/right/bottom/left
border_top/right/bottom/left_width, top/right/bottom/left
flex_grow, flex_shrink, z_index
border_top/right/bottom/left_color (u32 RGBA)
border_styles_packed (u16 — top/right/bottom/left)
border_spacing_h, border_spacing_v, tab_size

Tier 2b — CompactTextProps (24 bytes/node):

text_color, font_family_hash, line_height, letter_spacing, word_spacing, text_indent

Files with remaining direct CssPropertyCache access

File	Direct calls	Status
layout/src/solver3/fc.rs	23	height, shape_inside/outside, text_justify, line_height, hyphens, text_indent, column_count/gap, initial_letter, line_clamp, hanging_punctuation, text_combine_upright, exclusion_margin, hyphenation_language, table_layout, border_collapse (slow), border_spacing (slow), caption_side, border resolver
layout/src/solver3/taffy_bridge.rs	17	gap, grid_template_rows/columns/areas, grid_auto_rows/columns/flow, grid_column/row, flex_wrap, justify_items, justify_content, flex_grow/shrink, flex_basis, align_self, justify_self
layout/src/solver3/display_list.rs	12	cursor, opacity(×2), filter, backdrop_filter, box_shadow(×4), text_shadow, transform
layout/src/solver3/getters.rs	~30	border_radius(×12), background_content(×2), z_index, selection_, caret_, text_decoration, list_style, break_, orphans, widows, box_decoration_break, scrollbar_, user_select, font_family
layout/src/solver3/cache.rs	2	counter_reset, counter_increment
layout/src/hit_test.rs	1	cursor
layout/src/callbacks.rs	1	generic get_property()
core/src/styled_dom.rs	8	generic get_property(×6), background_content, position
core/src/gpu.rs	3	transform, transform_origin, opacity

Migration Plan — Property by Property

Phase 1: taffy_bridge.rs — Use existing getters + add new ones

These properties already have getters in getters.rs but taffy_bridge.rs bypasses them:

Property	Existing getter	taffy_bridge.rs line
FlexWrap	`get_wrap()`	L711
JustifyContent	`get_justify_content()`	L739

These need NEW getters in getters.rs:

Property	New getter name	Compact cache?	taffy_bridge.rs line
FlexGrow	`get_flex_grow()`	Yes (u16)	L751
FlexShrink	`get_flex_shrink()`	Yes (u16)	L763
FlexBasis	`get_flex_basis()`	Yes (u32_dim)	L773
AlignSelf	`get_align_self()`	No (Tier 3)	L798
JustifySelf	`get_justify_self()`	No (Tier 3)	L807
JustifyItems	`get_justify_items()`	No (Tier 3)	L729
Gap	`get_gap()`	No (Tier 3)	L550
GridTemplateRows	`get_grid_template_rows()`	No (Tier 3)	L571
GridTemplateColumns	`get_grid_template_columns()`	No (Tier 3)	L589
GridTemplateAreas	`get_grid_template_areas()`	No (Tier 3)	L607
GridAutoRows	`get_grid_auto_rows()`	No (Tier 3)	L638
GridAutoColumns	`get_grid_auto_columns()`	No (Tier 3)	L650
GridAutoFlow	`get_grid_auto_flow()`	No (Tier 3)	L667
GridColumn	`get_grid_column()`	No (Tier 3)	L680
GridRow	`get_grid_row()`	No (Tier 3)	L693

Phase 2: fc.rs — IFC/text properties + table properties

Need NEW getters in getters.rs:

Property	New getter name	Compact cache?	fc.rs line
Height (raw)	(use existing get_css_height)	Yes	L2538
ShapeInside	`get_shape_inside()`	No (Tier 3)	L2577
ShapeOutside	`get_shape_outside()`	No (Tier 3)	L2612
TextJustify	`get_text_justify()`	No (Tier 3)	L2642
LineHeight	`get_line_height()`	Yes (Tier 2b)	L2653
Hyphens	`get_hyphens()`	No (Tier 3)	L2660
TextIndent	`get_text_indent()`	Yes (Tier 2b)	L2706
ColumnCount	`get_column_count()`	No (Tier 3)	L2726
ColumnGap	`get_column_gap()`	No (Tier 3)	L2738
InitialLetter	`get_initial_letter()`	No (Tier 3)	L2774
LineClamp	`get_line_clamp()`	No (Tier 3)	L2793
HangingPunctuation	`get_hanging_punctuation()`	No (Tier 3)	L2801
TextCombineUpright	`get_text_combine_upright()`	No (Tier 3)	L2810
ExclusionMargin	`get_exclusion_margin()`	No (Tier 3)	L2822
HyphenationLanguage	`get_hyphenation_language()`	No (Tier 3)	L2831
TableLayout	`get_table_layout()`	No (Tier 3)	L3335
CaptionSide	`get_caption_side()`	No (Tier 3)	L3425

Phase 3: display_list.rs — Paint properties

Need NEW getters in getters.rs:

Property	New getter name	Compact cache?	display_list.rs line
Cursor	`get_cursor()`	No (Tier 3)	L1363
Opacity	`get_opacity()`	No (Tier 3)	L1730, L3415
Filter	`get_filter()`	No (Tier 3)	L1745
BackdropFilter	`get_backdrop_filter()`	No (Tier 3)	L1761
BoxShadowLeft	`get_box_shadow_left()`	No (Tier 3)	L2408
BoxShadowRight	`get_box_shadow_right()`	No (Tier 3)	L2409
BoxShadowTop	`get_box_shadow_top()`	No (Tier 3)	L2410
BoxShadowBottom	`get_box_shadow_bottom()`	No (Tier 3)	L2411
TextShadow	`get_text_shadow()`	No (Tier 3)	L2711
Transform	`get_transform()`	No (Tier 3)	L3430

Phase 4: getters.rs internal — Add compact fast paths where missing

Already in getters.rs but without compact fast path:

Property	Current getter	Add compact?
BorderRadius (×4)	`get_style_border_radius()`	No (Tier 3)
ZIndex	`get_z_index()`	Yes (i16 in Tier 2)
BackgroundContent	`get_background_color()` / `get_background_contents()`	No (Tier 3)
SelectionBgColor	`get_selection_style()`	No (Tier 3)
SelectionColor	`get_selection_style()`	No (Tier 3)
SelectionRadius	`get_selection_style()`	No (Tier 3)
CaretColor	`get_caret_style()`	No (Tier 3)
CaretWidth	`get_caret_style()`	No (Tier 3)
CaretAnimationDuration	`get_caret_style()`	No (Tier 3)
TextDecoration	`get_style_properties()`	No (Tier 3)
ListStyleType	`get_list_style_type()`	No (Tier 3)
ListStylePosition	`get_list_style_position()`	No (Tier 3)
BreakBefore	`get_break_before()`	No (Tier 3)
BreakAfter	`get_break_after()`	No (Tier 3)
BreakInside	`get_break_inside()`	No (Tier 3)
Orphans	`get_orphans()`	No (Tier 3)
Widows	`get_widows()`	No (Tier 3)
BoxDecorationBreak	`get_box_decoration_break()`	No (Tier 3)
ScrollbarStyle	`get_scrollbar_style()`	No (Tier 3)
ScrollbarWidth	`get_scrollbar_width_px()`	No (Tier 3)
ScrollbarColor	`get_scrollbar_style()`	No (Tier 3)
UserSelect	`is_text_selectable()`	No (Tier 3)
FontFamily	`collect_font_stacks_from_styled_dom()`	No (Tier 3)

Phase 5: cache.rs, hit_test.rs, callbacks.rs

Property	File	New getter name
CounterReset	cache.rs L2207	`get_counter_reset()`
CounterIncrement	cache.rs L2229	`get_counter_increment()`
Cursor	hit_test.rs L119	`get_cursor()` (reuse from Phase 3)
Generic	callbacks.rs L2420	Keep generic — this is public API

Phase 6: core/ files (gpu.rs, styled_dom.rs)

These are in core/, not layout/. They need to call getters too,
but getters.rs is in layout/. Options:

Move getters to core/ — complex, breaks layering
Keep core/ accesses as-is — they're cold-path (GPU compositing, devtools)
Add a thin wrapper in core/ — duplicates code

Decision: Keep core/ accesses as-is for now. They are cold-path,
and the eventual FxHash migration will handle them.

Implementation Order

Create plan (this file) ✅
Add new getters to getters.rs for ALL missing properties
Migrate taffy_bridge.rs to use all getters
Migrate fc.rs to use all getters
Migrate display_list.rs to use all getters
Migrate cache.rs to use getters
Migrate hit_test.rs to use getters
cargo check --package azul-layout
Run tests
Commit