Meter

Overview

Meter derives from native System.Windows.Controls.ProgressBar (NaviusMeter), restyled as a static, determinate readout rather than a progress operation: IsIndeterminate is coerced to always false, and Value is genuinely clamped into [Minimum, Maximum] by RangeBase’s own default coercion, unlike NaviusProgress’s deliberate “validate, don’t clamp” behavior.

Usage

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

<StackPanel>
    <navius:NaviusMeterLabel x:Name="DiskLabel" Text="Disk usage" />
    <navius:NaviusMeter x:Name="Disk"
                         Value="72"
                         Minimum="0"
                         Maximum="100"
                         AutomationProperties.LabeledBy="{Binding ElementName=DiskLabel}" />
    <navius:NaviusMeterValue Source="{Binding ElementName=Disk}" />
</StackPanel>

Properties

Property	Type	Default	From	Description
Value	double	0.0	ProgressBar (RangeBase)	Current value, clamped into [Minimum, Maximum] by the inherited default coercion (no override).
Minimum	double	0.0	ProgressBar (RangeBase)	Minimum value.
Maximum	double	100.0	NaviusMeter (overrides RangeBase)	A value <= Minimum falls back to Minimum + 100.
IsIndeterminate	bool	false (locked)	NaviusMeter (overrides ProgressBar)	Always coerced to false; setting it true is silently rejected. Meter is contractually always a static, determinate readout.
GetValueLabel	Func<double, string?>?	null	NaviusMeter	Builds the value text for the current value. Defaults to the rounded percentage plus "%".
Fraction	double	computed	NaviusMeter	Read-only, not a DP. 0..1, min-aware: (Value - Minimum) / (Maximum - Minimum).
Percentage	double	computed	NaviusMeter	Read-only, not a DP. Fraction * 100.
Source	NaviusMeter?	null	NaviusMeterValue	The meter instance whose formatted value text this element renders.
TextOverride	string?	null	NaviusMeterValue	When set, overrides the default rounded-percentage text.

Methods

Method	Description
FormatValueText()	Returns GetValueLabel or the default rounded percentage plus "%". Always non-null (unlike NaviusProgress.FormatValueText()), since Meter is never indeterminate.

Events

Event	Signature	Fires when
StateChanged	RoutedEventHandler	Value, Minimum, or Maximum changes; consumed by NaviusMeterValue to refresh its text.

UIA mechanism

NaviusMeterAutomationPeer (derives ProgressBarAutomationPeer) overrides GetItemStatusCore() to return FormatValueText(), mirroring NaviusProgressAutomationPeer. AutomationControlType stays the inherited ProgressBar value, since WPF has no distinct Meter automation type; this is an acknowledged platform gap, not an attempt to spoof a different control type. The inherited ProgressBarAutomationPeer’s IRangeValueProvider is already read-only (SetValue throws), matching the contract’s “no keyboard, no focus management.” The unit suite covers the clamping behavior (Value_IsClampedIntoRange_UnlikeProgress, Value_Negative_IsClampedToMinimum), the IsIndeterminate lock (IsIndeterminate_AlwaysCoercedToFalse), the Maximum <= Minimum fallback, default values, and the automation peer’s ItemStatus text.

Web deltas

• Value is genuinely clamped into [Minimum, Maximum] via RangeBase’s own default CoerceValueCallback (no override needed), the opposite choice from NaviusProgress’s “validate, don’t clamp” deviation.
• IsIndeterminate is locked to false via a CoerceValueCallback override, so the indeterminate-pulse visual/behavior from NaviusProgress is unreachable here; this also resolves the parity doc’s own concern about a screen reader announcing a static Meter as an active progress operation.
• Maximum <= Minimum falls back to Minimum + 100 (Meter’s own rule, distinct from Progress’s Maximum <= 0 -> 100).
• GetValueLabel is Func<double, string?>? (single parameter), matching the web contract exactly; no deviation here, unlike NaviusProgress’s two-parameter signature.
• AutomationControlType has no distinct “Meter” UIA value and stays the inherited ProgressBar value; disclosed platform gap, not a false claim.
• aria-labelledby wiring uses the same AutomationProperties.LabeledBy idiom as NaviusProgress, not a push-based context registration.

Captures

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