ScrollArea

Overview

ScrollArea derives directly from the native ScrollViewer and is re-templated with overlay scrollbars, inheriting native keyboard scrolling, mouse-wheel handling, and ScrollPattern automation support for free through standard part names. IsHovering and IsScrolling mirror the web contract’s hover/scroll fade state so the template can show and hide the bars without a hand-rolled state machine.

Usage

xmlns:navius="clr-namespace:Navius.Wpf.Primitives.Controls;assembly=Navius.Wpf.Primitives"

<navius:NaviusScrollArea ScrollHideDelay="600">
    <StackPanel>
        <!-- long content -->
    </StackPanel>
</navius:NaviusScrollArea>

Properties

Property	Type	Default	From	Description
IsHovering	bool	false	NaviusScrollArea	Read-only. true while the pointer is over the scroll area (real-time, no delay), driven by OnMouseEnter/OnMouseLeave.
IsScrolling	bool	false	NaviusScrollArea	Read-only. true while a scroll is in progress or within ScrollHideDelay milliseconds of the last one; reset by an internal DispatcherTimer.
ScrollHideDelay	int	600	NaviusScrollArea	Milliseconds of scroll inactivity before IsScrolling resets to false.
Content	object	-	ScrollViewer	The scrollable content.

Keyboard interactions

Key	Behavior
Arrow keys / Page Up / Page Down / Home / End	Native ScrollViewer keyboard scrolling, inherited unchanged; NaviusScrollArea intercepts no keys itself.

UIA mechanism

NaviusScrollArea ships no custom AutomationPeer and inherits the native ScrollViewerAutomationPeer (reports AutomationControlType.Pane and implements ScrollPattern) through the standard PART_ScrollContentPresenter/PART_VerticalScrollBar/ PART_HorizontalScrollBar part names declared in Themes/ScrollArea.xaml, so no OnApplyTemplate override was needed. The re-templated ScrollBar parts carry their own native ScrollBarAutomationPeer. The unit suite (ScrollAreaTests) verifies the IsHovering/IsScrolling state transitions, the ScrollHideDelay timer, and that the applied template exposes PART_ScrollContentPresenter/PART_VerticalScrollBar/PART_HorizontalScrollBar/ PART_Corner by name.

Web deltas

• The web family renders five separate parts (Root/Viewport/Scrollbar/Thumb/Corner) as plain divs with no ARIA roles at all; the WPF port collapses them onto one ScrollViewer-derived control plus its ControlTemplate. The native ScrollViewerAutomationPeer/ ScrollBarAutomationPeer pair is a strict accessibility upgrade over that ARIA-free baseline, not a gap.
• Thumb size/offset ratio math (ThumbSizeRatio/ThumbOffsetRatio, hand-rolled in the web’s JS) is not ported; the re-templated native ScrollBar’s own Track computes thumb geometry from TemplateBindings onto Value/Maximum/ViewportSize instead.
• The pointer-drag thumb gesture (a JS dragScrollThumb module on the web) is not ported; the native Thumb/Track drag-to-scroll behavior supersedes it entirely, including RTL handling (WPF’s FlowDirection is the framework-level RTL mechanism, not the web’s manual sign-flip).
• Type (auto/always/hover/scroll scrollbar-visibility mode) is not ported as a discrete property; only the hover/scroll fade behavior is implemented via IsHovering/IsScrolling triggers, with bar presence governed by native ScrollBarVisibility instead.
• ForceMount (keep a scrollbar mounted with no overflow) has no WPF equivalent property; Visibility is the only presence control.
• Dir/RTL thumb-offset sign-flip normalization is dropped; WPF’s FlowDirection already handles RTL layout at the framework level.
• M6 audit found no confirmed or plausible defects; the smaller ported surface (no Type, no ForceMount) is a deliberate scope reduction, not a behavioral gap.

Captures

The ScrollArea Gallery page rendered at the pinned commit, in each theme.