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Property & Event API Scrub — Control-by-Control Audit

Status: Implemented

Phases 0–8 of the implementation landed on branch feat/039-property-event-scrub; Phase 9 (docs) is landing in the same branch. The task list with the per-section breakdown and tracker lives at docs/specs/tasks/039-property-and-event-scrub-implementation.md.

Phase 0–8 commit history: git log feat/039-property-event-scrub --grep='Phase '.

This spec catalogs every control Reactor currently exposes through Microsoft.UI.Reactor.Factories and audits each against three criteria.

Decisions locked (from §15 open questions — final, will not change mid-implementation)

  • Q1 (source-gen vs hand-written): Hand-written, in src/Reactor/Elements/ElementExtensions.Events.cs. A source generator was considered but rejected to keep build infrastructure simple; the shapes are regular enough that a self-test in tests/Reactor.SelfTests/ enforces parity between callback properties and fluent extensions.

    C# naming constraint (discovered during implementation): The spec's literal .OnClick(handler) API cannot coexist with a delegate-typed property of the same name. C# binds el.OnClick(arg) to property-as- delegate invocation (Action?.Invoke(arg)) and never falls back to extension methods — see reactor3 issue #39. The fluent extensions therefore drop the On prefix and match the WinUI XAML event-name convention:

    • Property OnClick → Fluent .Click(handler)
    • Property OnTextChanged → Fluent .TextChanged(handler)
    • Property OnSelectedIndexChanged → Fluent .SelectedIndexChanged(handler)
    • …and so on across the inventory.

    This deviates from the spec's literal §0.1 wording but preserves the goal (every callback property is reachable via a fluent extension). The property names are unchanged, so existing property-init syntax (new ButtonElement(…) { OnClick = … }) continues to compile.

  • Q2 (null semantics): .OnX(null) clears any previously-set handler. No separate .WithoutOnX() helper.

  • Q3 (button styles): .AccentButton() / .SubtleButton() fluent extensions land in ElementExtensions.NamedStyles.cs.

  • Q4 (CalendarView multi-select): Distinct API for CalendarView — Action<IReadOnlyList<DateTimeOffset>>? OnSelectedDatesChanged plus an IReadOnlyList<DateTimeOffset>? SelectedDates init property.

  • Q5 (HyperlinkButton.NavigateUri): Add the fluent .NavigateUri(Uri) extension; the existing XML doc comment promise is fulfilled.

Goals

For every Reactor control surface, answer three questions:

  1. Event parity. Every event that can be passed as a factory positional/named argument should also be configurable via a fluent modifier extension (e.g. .OnClick(handler)), so users who construct elements via collection- initializer / property-syntax can wire events without Set().
  2. Property coverage. The commonly-used WinUI 2 / WinUI 3 properties should be first-class on the Reactor element (init-only property or fluent extension), so the default scenario never requires .Set(c => c.Foo = bar). .Set() is the escape hatch, not the primary API.
  3. Naming alignment. Property/factory/element-record names should match the WinUI control name they wrap, or the deviation should be a deliberate stylistic wrapper (e.g. Heading over TextBlock).

Methodology

Sources surveyed:

  • src/Reactor/Core/Element.cs (lines 1643–2948) — all element records.
  • src/Reactor/Elements/Dsl.cs — factory entry points.
  • src/Reactor/Elements/ElementExtensions.cs — fluent modifiers.
  • src/Reactor/Controls/**/ — specialized controls (AutoSuggest, DataGrid, MaskedTextField, PropertyGrid, VirtualList).

For each control the audit columns are:

Field Meaning
Factory Public DSL entry point in Factories
Element Backing record in Microsoft.UI.Reactor.*
WinUI target Native control wrapped (or "(custom)" if Reactor-original)
Events on element All Action/Action<T> callbacks (factory args + init properties)
Events with fluent Which of those events also have a .OnX(handler) extension
Missing common properties WinUI properties used by >50% of real-world WinUI samples that are not surfaced as either an init property or a fluent extension
Naming notes Deliberate deviation from WinUI name (justified or not)

§0 Cross-cutting findings

0.1 Event-handler fluent extensions are universally missing

The grep below returns zero hits in the entire src/Reactor tree:

rg -n "public static.*OnClick" src/Reactor

There is no .OnClick(...) extension on ButtonElement. There is no .OnTextChanged(...) on TextFieldElement. There is no .OnValueChanged(...) on SliderElement / NumberBoxElement / RatingControlElement. Every event listed in §1–§9 below is only reachable through the factory's positional parameter list or by the property-initializer syntax (new ButtonElement("X") { OnClick = ... }). For users who prefer the fluent style Button("Save").Margin(8).Bold().OnClick(...), the chain breaks at the event.

This is a systemic gap, not a per-control miss. The fix is mechanical: emit one OnX extension per element-record callback property. Recommended approach is a single fluent-extensions file (ElementExtensions.Events.cs) or — since the shapes are extremely regular — a source generator that walks records and emits one extension per Action/Action<T> member.

Estimated count of missing extensions: ~60 across all controls (see §1–§9).

0.2 Setters pattern is consistent — good

Every wrapper element exposes an internal Setters array and a public Set(...) extension. The pattern is uniform across all ~70 wrapper records. No change needed; this is the right escape hatch.

0.3 Reactor-original wrappers are clearly named — good

Heading / SubHeading / Caption over TextBlock, VStack / HStack over StackPanel, Flex / FlexRow / FlexColumn (Yoga-based, no WinUI equivalent), LazyVStack<T> / LazyHStack<T> (ItemsRepeater wrappers), TemplatedListView<T> etc. — these are deliberate React-/SwiftUI-style affordances and the deviation is justified. Calling these out in doc comments would help discoverability but is not a blocker.

0.4 A handful of properties shadow WinUI names with different types

SwipeControlElement.LeftItemsMode is SwipeMode (matches WinUI). But StackElement.Spacing defaults to 8 while WinUI's StackPanel.Spacing defaults to 0 — a deliberate but undocumented opinionated default. Worth calling out in remediation: keep the default, but document it.

§1 Text & Rich Text

1.1 TextBlock → Microsoft.UI.Xaml.Controls.TextBlock

Field Status
Factory TextBlock(string content)
Element TextBlockElement(string Content)
Events on element (none)
Events with fluent n/a
Init properties FontSize, Weight, FontStyle, HorizontalAlignment, TextWrapping, TextAlignment, TextTrimming, IsTextSelectionEnabled, FontFamily
Fluent extensions Bold, SemiBold, FontSize, FontStyle, TextWrapping, TextAlignment, TextTrimming, Selectable, FontFamily
Missing common WinUI properties Foreground (have generic .Foreground() on Element — OK), LineHeight, MaxLines, CharacterSpacing, TextDecorations, Inlines (would require new model)
Naming notes Matches WinUI exactly. Weight is short for FontWeight — minor inconsistency with WinUI's FontWeight.

1.2 Heading / SubHeading / Caption (Reactor-original stylized TextBlocks)

Field Status
Factory Heading(string), SubHeading(string), Caption(string)
Element TextBlockElement with preset FontSize / Weight / heading-level
Naming notes Deliberate. Justified: Fluent UI / Material / SwiftUI all have a typography scale; mirroring TextBlock styles requires Style="{StaticResource TitleTextBlockStyle}". Recommend: extend the family — Title, Subtitle, Body, BodyStrong, BodyLarge to align with the WinUI 3 type ramp.

1.3 RichText → Microsoft.UI.Xaml.Controls.RichTextBlock

Field Status
Factory RichText(string), RichText(RichTextParagraph[])
Element RichTextBlockElement(string Text) + Paragraphs[]
Events (none)
Init properties FontSize, Paragraphs, IsTextSelectionEnabled, TextWrapping
Missing common properties MaxLines, LineHeight, OverflowContentTarget (links to a continuation), TextAlignment, TextTrimming, CharacterSpacing
Naming notes Reactor uses RichText; WinUI uses RichTextBlock. Mild — consider renaming or alias.

1.4 RichEditBox → Microsoft.UI.Xaml.Controls.RichEditBox

Field Status
Factory RichEditBox(string text, Action<string>? onTextChanged)
Element RichEditBoxElement(string Text) with OnTextChanged init
Events on element OnTextChanged
Events with fluent ❌ Missing .OnTextChanged(...)
Init properties IsReadOnly, Header, PlaceholderText, OnTextChanged
Missing common properties IsSpellCheckEnabled, MaxLength, TextWrapping, AcceptsReturn, SelectionHighlightColor, Document access
Naming notes Matches WinUI exactly.

§2 Buttons

2.1 Button → Microsoft.UI.Xaml.Controls.Button

Field Status
Factory Button(string label, Action? onClick), Button(Element content, Action? onClick), Button(Command)
Element ButtonElement(string Label, Action? OnClick)
Events on element OnClick
Events with fluent ❌ Missing .OnClick(...) (the canonical example raised by the user)
Init properties IsEnabled, IsDisabledFocusable, ContentElement
Fluent extensions DisabledFocusable, Disabled (generic)
Missing common properties Style (currently only via .ApplyStyle() — fine), Flyout (have .WithFlyout() — OK), CornerRadius (generic ✓), Padding (generic ✓). Real gap: no .AccentStyle() / .SubtleStyle() shortcut for the very common AccentButtonStyle / SubtleButtonStyle resources.
Naming notes Matches WinUI exactly.

2.2 HyperlinkButton → Microsoft.UI.Xaml.Controls.HyperlinkButton

Field Status
Factory HyperlinkButton(string content, Uri? navigateUri, Action? onClick), HyperlinkButton(Command)
Element HyperlinkButtonElement(string Content, Uri? NavigateUri, Action? OnClick)
Events on element OnClick
Events with fluent ❌ Missing .OnClick(...)
Init properties —
Missing common properties NavigateUri is constructor-only; no fluent .NavigateUri(...) despite the XML doc on Button(Command) instructing users to "combine with .NavigateUri(...) via .Set()" — the comment promises an API that doesn't exist. Fix the doc or add the extension.
Naming notes Matches.

2.3 RepeatButton → Microsoft.UI.Xaml.Controls.Primitives.RepeatButton

Field Status
Factory RepeatButton(string label, Action? onClick), RepeatButton(Command)
Element RepeatButtonElement with Delay=250, Interval=50
Events on element OnClick
Events with fluent ❌ Missing
Fluent extensions Delay, Interval ✓
Missing common properties covered
Naming notes Matches.

2.4 ToggleButton → Microsoft.UI.Xaml.Controls.Primitives.ToggleButton

Field Status
Factory ToggleButton(string label, bool isChecked, Action<bool>? onIsCheckedChanged), ToggleButton(Command, bool isChecked)
Events on element OnIsCheckedChanged
Events with fluent ❌ Missing .OnIsCheckedChanged(...)
Missing common properties IsThreeState + IsChecked as nullable (WinUI exposes bool? to support indeterminate). Reactor only supports two states.
Naming notes Matches.

2.5 DropDownButton, SplitButton, ToggleSplitButton

Field Status
Factory All match WinUI names.
Events on element SplitButton: OnClick; ToggleSplitButton: OnIsCheckedChanged
Events with fluent ❌ Missing across all three
Missing common properties Flyout is constructor-only; could be fluent.
Naming notes Matches.

§3 Input controls

3.1 TextField → Microsoft.UI.Xaml.Controls.TextBox

Field Status
Factory TextField(string value, Action<string>? onChanged, string? placeholder, string? header)
Element TextFieldElement(string Value, Action<string>? OnChanged, string? Placeholder)
Events on element OnChanged, OnSelectionChanged
Events with fluent ❌ Both missing
Init properties Header, IsReadOnly, AcceptsReturn, TextWrapping, SelectionStart, SelectionLength
Fluent extensions ReadOnly, AcceptsReturn, TextWrapping, Header
Missing common properties MaxLength, InputScope (numeric/email/url/etc — very common), IsSpellCheckEnabled, CharacterCasing, TextAlignment, Description (text under the box)
Naming notes Deliberate deviation. WinUI is TextBox; Reactor uses TextField (matches SwiftUI / Fluent UI React / MUI). Justified — TextField is the more universally recognized name. Worth documenting prominently. See §16 for a detailed collision analysis if we ever reconsider the rename.

3.2 PasswordBox → Microsoft.UI.Xaml.Controls.PasswordBox

Field Status
Factory PasswordBox(string password, Action<string>? onPasswordChanged, string? placeholderText)
Events on element OnPasswordChanged
Events with fluent ❌ Missing
Init properties (just constructor args + Setters)
Missing common properties MaxLength, Header, PasswordRevealMode, PasswordChar, InputScope
Naming notes Matches.

3.3 NumberBox → Microsoft.UI.Xaml.Controls.NumberBox

Field Status
Factory NumberBox(double value, Action<double>? onValueChanged, string? header)
Events on element OnValueChanged
Events with fluent ❌ Missing
Init properties Minimum, Maximum, PlaceholderText, SpinButtonPlacement, SmallChange, LargeChange
Fluent extensions Range, SpinButtons
Missing common properties NumberFormatter (formatting decimal places — common), AcceptsExpression, ValidationMode, Description
Naming notes Matches. Range(min,max) is a Reactor convenience helper — keep.

3.4 AutoSuggestBox → Microsoft.UI.Xaml.Controls.AutoSuggestBox

Field Status
Factory AutoSuggestBox(string text, Action<string>? onTextChanged, Action<string>? onQuerySubmitted)
Events on element OnTextChanged, OnQuerySubmitted, OnSuggestionChosen (init-only, NOT in factory)
Events with fluent ❌ All three missing
Init properties Suggestions, PlaceholderText
Missing common properties Header, QueryIcon, IsSuggestionListOpen (manual control), TextMemberPath / DisplayMemberPath (for non-string suggestions — would need richer model — see also the typed AutoSuggestElement<T> in Controls/AutoSuggest/)
Naming notes Matches. Bug-worthy: OnSuggestionChosen is reachable only via property-init syntax — neither factory nor fluent.

3.5 CheckBox / ThreeStateCheckBox → Microsoft.UI.Xaml.Controls.CheckBox

Field Status
Factory CheckBox(bool isChecked, Action<bool>? onIsCheckedChanged, string? label), ThreeStateCheckBox(bool? checkedState, Action<bool?>? onCheckedStateChanged, string? label)
Events on element OnIsCheckedChanged, OnCheckedStateChanged
Events with fluent ❌ Both missing
Naming notes Matches. Splitting two/three-state into two factories is a Reactor convenience — fine.

3.6 RadioButton, RadioButtons

Field Status
Factory RadioButton(label, isChecked, onIsCheckedChanged, groupName), RadioButtons(string[] items, int selectedIndex, Action<int>? onSelectedIndexChanged)
Events OnIsCheckedChanged / OnSelectedIndexChanged
Events with fluent ❌ Missing
Missing common properties RadioButtons: MaxColumns, Header (already there), ItemTemplate (would need typed overload)
Naming notes Matches.

3.7 ComboBox → Microsoft.UI.Xaml.Controls.ComboBox

Field Status
Factory ComboBox(string[] items, int selectedIndex, Action<int>? onSelectedIndexChanged), ComboBox(Element[] itemElements, ...)
Events on element OnSelectedIndexChanged
Events with fluent ❌ Missing
Init properties PlaceholderText, Header, IsEditable, ItemElements
Fluent extensions Placeholder, Editable, Header
Missing common properties MaxDropDownHeight, Description, DropDownOpened/DropDownClosed events
Naming notes Matches.

3.8 Slider → Microsoft.UI.Xaml.Controls.Slider

Field Status
Factory Slider(double value, double min, double max, Action<double>? onValueChanged)
Events on element OnValueChanged
Events with fluent ❌ Missing
Init properties StepFrequency, Header
Fluent extensions StepFrequency, Header
Missing common properties Orientation, TickFrequency, TickPlacement, SnapsTo, IsThumbToolTipEnabled, ThumbToolTipValueConverter
Naming notes Matches.

3.9 ToggleSwitch → Microsoft.UI.Xaml.Controls.ToggleSwitch

Field Status
Factory ToggleSwitch(bool isOn, Action<bool>? onIsOnChanged, string? onContent, string? offContent, string? header)
Events on element OnIsOnChanged
Events with fluent ❌ Missing
Init properties Header
Fluent extensions Header
Missing common properties OffContent/OnContent as Element (not just string), IsEnabled (generic ✓)
Naming notes Matches.

3.10 RatingControl → Microsoft.UI.Xaml.Controls.RatingControl

Field Status
Events OnValueChanged
Events with fluent ❌ Missing
Missing common properties Caption is init but no fluent. PlaceholderValue, InitialSetValue
Naming notes Matches.

3.11 ColorPicker → Microsoft.UI.Xaml.Controls.ColorPicker

Field Status
Events OnColorChanged
Events with fluent ❌ Missing
Init properties IsAlphaEnabled, IsMoreButtonVisible, IsColorSpectrumVisible, IsColorSliderVisible, IsColorChannelTextInputVisible, IsHexInputVisible
Fluent extensions none (only .Set())
Missing common properties All six init properties have no fluent equivalent. Also missing: ColorSpectrumShape, MinHue/MaxHue/MinSaturation/MaxSaturation/MinValue/MaxValue
Naming notes Matches.

§4 Date & Time

4.1 CalendarDatePicker, DatePicker, TimePicker, CalendarView

Control Events Fluent? Notable gaps
CalendarDatePicker OnDateChanged ❌ DateFormat, IsTodayHighlighted, IsCalendarOpen, IsGroupLabelVisible
DatePicker OnDateChanged ❌ DayFormat, MonthFormat, YearFormat, Orientation, DayPicker/MonthPicker/YearPicker order
TimePicker OnTimeChanged ❌ Header (init only, no fluent), no event fluent
CalendarView none modeled n/a SelectedDatesChanged (the only meaningful event — missing entirely), MinDate/MaxDate, FirstDayOfWeek, NumberOfWeeksInView, DisplayMode

CalendarView is the worst offender in this section — it wraps a control whose entire purpose is letting users select dates, but Reactor exposes no SelectedDates collection and no OnSelectedDatesChanged event. Currently unreachable except via .Set().

§5 Progress & Status

Control Events Fluent? Notable gaps
Progress (ProgressBar) none n/a matches WinUI sufficiently
ProgressRing none n/a covered
InfoBar OnActionButtonClick, OnClosed ❌ both IconSource (custom icon), Content (element child)
InfoBadge none n/a IconSource, Background (have generic ✓)

Naming note: Progress (Reactor) vs ProgressBar (WinUI). Minor deviation — the factory name dropped "Bar" for brevity. The ProgressIndeterminate() helper is a Reactor-original convenience. Worth documenting.

§6 Layout containers

Control WinUI target Events Events with fluent Notable gaps
VStack/HStack (StackElement) StackPanel none n/a matches
WrapGrid (WrapGridElement) VariableSizedWrapGrid none n/a ColumnSpan/RowSpan attached props
Grid (GridElement) Grid none n/a covered
ScrollView ScrollViewer none on element — Missing ViewChanged event entirely. Generic OnSizeChanged exists but scroll-position changes are unreachable.
Border Border none n/a covered
Expander Expander OnIsExpandedChanged ❌ ExpandDirection ✓, HeaderTemplate, ContentTransitions
SplitView SplitView OnPaneOpenChanged ❌ PaneBackground, LightDismissOverlayMode
Viewbox Viewbox none n/a StretchDirection
Canvas Canvas none n/a covered
Flex/FlexRow/FlexColumn (custom, Yoga) none n/a Reactor-original; covered
RelativePanel RelativePanel none n/a attached-property-only, fine via .RelativeTo() helpers

Naming notes:

  • VStack/HStack over StackPanel — deliberate (SwiftUI-style), justified.
  • ScrollView over ScrollViewer — minor; consider an alias or rename.

§7 Navigation

7.1 NavigationHost<TRoute> (Reactor-original)

Field Status
Element NavigationHostElement
Events none (handled by Navigation.NavigationHandle)
Init properties Transition, CacheMode, CacheSize
Naming notes Reactor-original — no WinUI equivalent.

7.2 NavigationView → Microsoft.UI.Xaml.Controls.NavigationView

Field Status
Events on element OnSelectedTagChanged, OnBackRequested
Events with fluent ❌ both missing (note: there is a Navigation-handle binding helper that auto-wires both, but the manual handler path has no fluent)
Fluent extensions PaneDisplayMode, PaneTitle
Missing common properties AutoSuggestBox slot, PaneFooter, PaneCustomContent, MenuItemsSource (already partly via MenuItems[]), OpenPaneLength, CompactModeThresholdWidth, ExpandedModeThresholdWidth

7.3 TitleBar → Microsoft.UI.Xaml.Controls.TitleBar (WinUI 3 1.5+)

Field Status
Events OnBackRequested, OnPaneToggleRequested
Events with fluent ❌ both missing
Init properties Subtitle, IsBackButtonVisible, IsBackButtonEnabled, IsPaneToggleButtonVisible, Content, RightHeader, Icon
Fluent extensions Subtitle only
Missing common properties most init properties have no fluent — IsBackButtonVisible / IconSource / RightHeader are the most-used

7.4 TabView → Microsoft.UI.Xaml.Controls.TabView

Field Status
Events OnSelectedIndexChanged, OnTabCloseRequested, OnAddTabButtonClick
Events with fluent ❌ all three missing
Fluent extensions ShowAddButton only
Missing common properties TabWidthMode, CloseButtonOverlayMode, CanDragTabs, CanReorderTabs, AllowDropTabs, TabStripHeader/TabStripFooter

7.5 BreadcrumbBar, Pivot, Frame

Control Events Fluent? Notable gaps
BreadcrumbBar OnItemClicked (factory arg) ❌ ItemTemplate
Pivot OnSelectedIndexChanged ❌ LeftHeader/RightHeader, HeaderTemplate, IsHeaderItemsCarouselEnabled
Frame none modeled n/a Navigated/Navigating/NavigationFailed events all missing; users must .Set()

§8 Collection controls

Control Events Fluent? Notable gaps
ListView OnSelectedIndexChanged, OnItemClick ❌ both IsItemClickEnabled (implicit), ItemContainerStyle, GroupStyle, IncrementalLoadingTrigger
GridView OnSelectedIndexChanged, OnItemClick ❌ both same as ListView
TreeView OnItemInvoked, OnExpanding ❌ both Collapsed event, ItemTemplate, drag/drop properties exist but no event fluents
FlipView OnSelectedIndexChanged ❌ UseTouchAnimationsForAllNavigation, MaxItems
ListBox OnSelectedIndexChanged ❌ SelectionMode, multi-select indexes, header/footer
ItemsView<T> OnItemInvoked ❌ IsItemInvokedEnabled ✓; missing ScrollView slot access, Layout (have LayoutKind enum — fine)
SemanticZoom none modeled n/a ViewChangeStarted/Completed missing
TemplatedListView<T>/TemplatedGridView<T>/TemplatedFlipView<T> OnSelectedIndexChanged, OnItemClick ❌ same as non-templated
LazyVStack<T>/LazyHStack<T> none n/a Reactor-original wrapper around ItemsRepeater

Universal gap: No collection control exposes SelectionChanged as a multi- selection event (only by-index). For SelectionMode != Single, users have no typed entry point. Track as a follow-up.

§9 Dialogs, overlays, flyouts, menus

Control Events Fluent? Notable gaps
ContentDialog OnClosed(ContentDialogResult) ❌ IsPrimaryButtonEnabled/IsSecondaryButtonEnabled, PrimaryButtonCommand patterns, Opened/Opening events
Flyout OnOpened, OnClosed ❌ both ShowMode, AreOpenCloseAnimationsEnabled, OverlayInputPassThroughElement
TeachingTip OnActionButtonClick, OnClosed ❌ both IconSource, HeroContent, PlacementMargin, PreferredPlacement
Popup OnClosed ❌ Opened event missing entirely
InfoBar (see §5)
MenuBar/CommandBar/MenuFlyout/CommandBarFlyout none modeled at element level (events live on MenuFlyoutItemData records) n/a Opening/Closing for flyouts unmodeled. CommandBar.IsOpenChanged unmodeled.

§10 Media

Control Events Fluent? Notable gaps
Image none n/a ImageOpened/ImageFailed, NineGrid
PersonPicture none n/a covered (DisplayName/Initials/ProfilePicture/IsGroup/BadgeNumber all available)
WebView2 OnNavigationStarting(Uri), OnNavigationCompleted(Uri) ❌ both WebMessageReceived, CoreWebView2Initialized, Source is init-only
MediaPlayerElement none modeled n/a MediaPlayer.MediaOpened/MediaEnded/MediaFailed unreachable
AnimatedVisualPlayer none modeled n/a Loaded, no playback control surface
AnimatedIcon none n/a State (init-only enum string property would help)

§11 Shapes

Control Events Notable gaps
Rectangle none covered
Ellipse none covered
Line none covered (X1/Y1/X2/Y2 ✓)
Path none StrokeStartLineCap, StrokeEndLineCap, StrokeLineJoin, StrokeMiterLimit, StrokeDashCap, StrokeDashOffset, FillRule

Naming and structure match WinUI Shapes. Path has the most gaps because it has the most native properties.

§12 Niche / less-common

Control Events Notes
SelectorBar OnSelectedIndexChanged ❌ no fluent
PipsPager OnSelectedPageIndexChanged ❌ no fluent. Missing WrapMode, MaxVisiblePips, PreviousButtonVisibility, NextButtonVisibility
AnnotatedScrollBar none modeled the entire DetailLabelRequested + ScrollingAnimationStarting surface is absent
RefreshContainer OnRefreshRequested ❌ no fluent. PullDirection missing
SwipeControl none on element (events on SwipeItemData.OnInvoked) covered
ParallaxView none VerticalShift/HorizontalShift ✓, missing Source (binding target), VerticalSourceStartOffset/EndOffset
MapControl none modeled The entire Maps API surface (Center, MapElements, ViewChanged) is unreachable

§13 Specialized Reactor controls

These are Reactor-original (no WinUI equivalent) so naming is "match itself."

Control File Notes
AutoSuggestElement<T> Controls/AutoSuggest/ Typed peer of AutoSuggestBox — different from AutoSuggestBoxElement. Audit separately.
DataGridElement<T> Controls/DataGrid/ First-party data grid. Audit separately.
MaskedTextFieldElement Controls/MaskedTextBox/ First-party. Folder is MaskedTextBox/ but the type/factory are MaskedTextField. If/when we resolve the TextField-vs-TextBox deviation (§3.1 / §16), the natural follow-on is MaskedTextField → MaskedTextBox so folder/type/factory all agree. WinForms also names this control MaskedTextBox. Audit otherwise separately.
PropertyGridElement Controls/PropertyGrid/ First-party. Audit separately.
VirtualListElement Controls/Virtualization/ Generic virtualization. Audit separately.

Recommend a follow-up spec 040-specialized-control-scrub that runs the same three checks against these five.

§14 Summary — recommended remediation order

Ordered roughly by user-visible impact:

  1. Generate On… fluent extensions for every event-callback element property. Single change touching one file (or one source generator). Closes the universal §0.1 gap, ~60 extension methods. No semantic change; pure ergonomic win.
  2. Promote frequently-set init properties to fluent extensions for the highest- traffic controls (Slider, NumberBox, ColorPicker, TabView, NavigationView, TitleBar, TextField). Most of these have rich init surfaces but only one or two fluent helpers.
  3. Model the missing events on CalendarView, Frame, ScrollView, Popup, MediaPlayerElement, WebView2 — these have meaningful events that are currently unreachable without .Set(). Spec-level decision on each.
  4. Common-property gaps with high traffic: TextField.InputScope, TextField.MaxLength, Slider.TickFrequency/Orientation, NumberBox.NumberFormatter, ContentDialog.IsPrimaryButtonEnabled, RichTextBlock.MaxLines, TabView.TabWidthMode/CanReorderTabs.
  5. Fix the HyperlinkButton(Command) doc comment that promises a .NavigateUri(...) extension that does not exist.
  6. Add type-ramp factories alongside Heading/SubHeading/Caption: Title, Subtitle, Body, BodyStrong, BodyLarge, matching the WinUI 3 type ramp.
  7. Specialized controls audit — separate spec 040, covering AutoSuggest, DataGrid, MaskedTextField, PropertyGrid, VirtualList.
  8. Fix the RichText to be RichTextBlock, consistent with TextBlock and the WinUI RichTextBlock control.

§15 Open questions

  1. Should event extensions be hand-written or source-generated? Pro source-gen: keeps shapes consistent and stays in sync as records evolve. Con: another moving piece.

  2. For nullable callbacks (Action<bool>?), should .OnX(null) clear a previously-set handler, or should we offer a separate .WithoutOnX()? The record-init pattern already permits clearing; a fluent null-passing convention is fine. A: null -> clear, is good

  3. Should we add .AccentButton() / .SubtleButton() as fluent shortcuts for the very common WinUI button styles, or insist users go through .ApplyStyle? A: .AccentButton()/.SubtleButton()... or "AccentButton()", etc., similar to the Heading/etc. for TextBlock.

  4. CalendarView.OnSelectedDatesChanged — multi-selection requires returning a DateTimeOffset[]. The reactor pattern so far has been "single-index ints", so multi-select calendars need a deliberate shape decision. A: I'm OK with having distinct API for CalendarView

  5. Do we want a fluent .NavigateUri(...) extension on HyperlinkButton, or fix the doc comment to point at the constructor arg? A: add the fluent API .

§16 Investigation — TextField → TextBox rename (and MaskedTextField → MaskedTextBox)

The §3.1 naming deviation surfaces a recurring question: should Reactor align with the WinUI name (TextBox) instead of the React-/SwiftUI-flavored TextField? This section captures the mechanical impact in case the policy choice changes later. No rename is recommended at this time — the deviation argument in §3.1 stands. This is reference material.

16.1 In-tree impact

  • ~578 source occurrences of TextField across ~100+ files: samples, tests, docs/guides, skills/recipes, plugins, pipeline templates.
  • Hardcoded factory-name strings that drive analyzers / tooling and would need updating in lockstep:
    • src/Reactor.Analyzers/AccessibilityAnalyzers.cs:198 — input-control factory-name hashset.
    • src/Reactor.Cli/Loc/LocalizableStringScanner.cs:27, :136 — localization scanner keys on the method name.
  • 165 files combine using static Microsoft.UI.Reactor.Factories; with using Microsoft.UI.Xaml.Controls; — the only scopes where collision is possible.

16.2 Compile-time collisions

TextBoxElement (renamed record) does not collide with WinUI's TextBox type — different bare names. The factory method Factories.TextBox(...) would share the bare name TextBox with the WinUI type in those 165 files. C# context-resolves most cases:

Usage Resolution Risk
TextBox("value", onChanged) Reactor factory method ✅ unambiguous
new TextBox() WinUI type ✅ unambiguous
(TextBox)x, typeof(TextBox), Foo<TextBox> WinUI type ✅ unambiguous
.Set(tb => …) inside a Reactor element tb is type-inferred ✅ no naming needed
nameof(TextBox) Ambiguous between type and method group ⚠️ user footgun (0 hits today)
Action<string> a = TextBox; Method-group conversion to factory ⚠️ resolves but surprises

Inside Reactor itself the library does not use using static Factories;, so the library code (Reconciler, ElementPool, etc.) is unaffected.

16.3 The MaskedTextField companion rename

If TextField is ever renamed to TextBox, MaskedTextField should rename to MaskedTextBox in the same change:

  • The folder is already src/Reactor/Controls/MaskedTextBox/ — the type name is the only thing inconsistent today.
  • The Windows-platform name for this control is MaskedTextBox (WinForms).
  • Bundling the two renames avoids a second migration pass.
  • No collision: MaskedTextBoxElement ≠ any WinUI / WinForms type name, and no WinUI control method named MaskedTextBox exists.

16.4 Migration options (if/when we do it)

  • A. Hard cutover. Compile-clean rename across the 578 occurrences. Live with the nameof footgun (document it).
  • B. [Obsolete] forwarding alias for one release. TextField stays as a thin wrapper calling TextBox (and same for TextFieldElement → TextBoxElement, MaskedTextField → MaskedTextBox). Lets external users migrate without breaking; we strip the aliases the release after.
  • C. Don't rename. The deliberate-deviation argument in §3.1 stands; action shrinks to one XML-doc-comment line on the TextField factory explaining the naming choice. Currently recommended.

16.5 Decision

Keep TextField and MaskedTextField as-is for now (option C). Record the deviation in the doc comments. If we revisit later, bundle both renames together and pick (B) for the migration path. This subsection is the reference for the impact analysis.

§17 Named-style fluent helpers

Sitting alongside .AccentButton() / .SubtleButton() (§15 Q3), these promote frequently-used WinUI named styles or enum-property values to fluent helpers, so the common case never requires .ApplyStyle("…") or a verbose init-property assignment. Each one is a single-line extension; the savings are discoverability and IntelliSense surface area, not lines of code per call site.

Decision rule (mirrors §15 Q3): when both a factory and a fluent could plausibly exist, pick whichever matches the precedent — fluent for style decorations that compose with any element of a family, factory for shape- changing wrappers like Heading/Card.

17.1 .AccentButton() / .SubtleButton() — Button and subtypes

  • Promotes AccentButtonStyle / SubtleButtonStyle resources.
  • Fluent, not factory — works on any ButtonBase-derived element (Button, DropDownButton, SplitButton). Style choice is decoration, not a different element shape.

17.2 .TextLink() — HyperlinkButton (and Button)

  • Promotes TextBlockButtonStyle — chromeless inline-link style. The canonical "Learn more" rendering inside paragraphs.
  • Fluent. Most common on HyperlinkButton; consider an overload for Button too since TextBlockButtonStyle is defined for the base Button class in WinUI.
  • Naming: .TextLink() reads better than .AsTextLink() or .TextBlockStyle().

17.3 .NumericInput() / .EmailInput() / .UrlInput() / .PhoneInput() / .SearchInput() — TextField (and PasswordBox where applicable)

  • Promotes InputScope / InputScopeNameValue enum values. Not a "style" in the WinUI sense, but the same ergonomic problem — verbose enum names (InputScopeNameValue.EmailSmtpAddress) that nobody types by hand.
  • Fluent. Mirrors React Native's keyboardType="numeric" and HTML's <input type="email">.
  • Mapping:
    • .NumericInput() → InputScopeNameValue.Number
    • .EmailInput() → InputScopeNameValue.EmailSmtpAddress
    • .UrlInput() → InputScopeNameValue.Url
    • .PhoneInput() → InputScopeNameValue.TelephoneNumber
    • .SearchInput() → InputScopeNameValue.Search
  • Generic .InputScope(InputScopeNameValue) escape hatch surfaces the long tail (Chat, FormulaNumber, AlphanumericFullWidth, etc.) — same relationship .ApplyStyle() has to .AccentButton(). Decided: include the escape hatch.

17.4 .Informational() / .Success() / .Warning() / .Error() — InfoBar

  • Promotes InfoBarSeverity enum values. The InfoBar visually re-skins per severity (icon + accent color), so this is the closest analogue to a named style.
  • Fluent. Mirrors React/Fluent UI's <Alert severity="error">.
  • All four severities map 1:1 to InfoBarSeverity members; same naming as the enum minus the type prefix.

17.5 Card(Element child) factory — Reactor-original

  • No WinUI named style equivalent — there is no CardStyle. But the canonical card composition (corner radius 8, CardBackgroundFillColorDefaultBrush, ~16 padding, subtle 1px stroke) is written by hand in nearly every WinUI app today.
  • Factory returning BorderElement — matches the Heading precedent exactly: Heading(string) returns a preset TextBlockElement; Card(child) returns a preset BorderElement. Lets you write Card(VStack(…)) directly and still chain any Border fluent extension (.Padding, .CornerRadius, .Background, .WithBorder) to override the preset.
  • Defaults pull from theme resources (CardBackgroundFillColorDefaultBrush, CardStrokeColorDefaultBrush, theme-aware corner radius), not literals, so the card re-themes correctly (light/dark, contrast modes).

17.6 Items deliberately NOT promoted

  • TextBlock type ramp (Title/Subtitle/Body/BodyStrong/BodyLarge) — already factories per §14 #6. Don't also add fluents (two-ways trap).
  • Progress .ShowError() / .Paused() — too narrow; the existing init properties are already cheap to set, and the names don't add discoverability the way severity does.
  • NavigationView/TitleBar/TabView pane-display modes etc. — already enum-typed init properties with reasonable names; no ergonomic gap.

17.7 Implementation note

All items above — 2 fluents in 17.1, 1 (or 2) in 17.2, 5 named-input fluents plus 1 generic escape-hatch in 17.3, 4 fluents in 17.4, and 1 factory in 17.5 — fit into the same ElementExtensions.NamedStyles.cs file (and Factories.NamedStyles.cs for the Card factory, sitting next to where Heading/SubHeading/Caption live today). Trivial to land in one PR alongside §14 #1 (the On… fluent generator).

The Card factory is the only item that needs a theme-resource lookup — the others are pure property assignments. Lift the brush/stroke lookup into a small helper so light/dark/contrast switches re-resolve through the existing ThemeResource plumbing rather than baking literals.