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The Currency Converter is a specialized category within the Unit Converter that provides real-time currency exchange rate conversions.

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Overview

Currency conversion in Windows Calculator uses live exchange rate data from Bing to provide accurate, up-to-date conversions between world currencies.
Developer Builds: Currency converter uses mock data with fictional planet names instead of real countries. This mock data remains static regardless of inputs and is clearly identifiable.
Source Reference: README.md:64-68

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Features

Live Exchange Rates

Real-time rates from Bing (retail builds only)

Dual Conversion

Convert in both directions simultaneously

Cached Data

Works offline with last downloaded rates

Multiple Currencies

Support for major world currencies

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Currency Data Management

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Automatic Updates

The currency converter intelligently manages exchange rate data:
  1. On First Use - Attempts to load from cache
  2. If Cache Miss - Downloads latest rates from Bing
  3. On Subsequent Uses - Checks cache freshness
  4. Auto-refresh - Updates when data is stale
Source Reference: src/CalcManager/UnitConverter.h:198-201

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Manual Refresh

Click the refresh button to:
  • Force download of latest rates
  • Update timestamp
  • Refresh all displayed conversions
Source Reference: src/Calculator/Views/UnitConverter.xaml.cs:167-180
The refresh button is disabled while a refresh operation is in progress to prevent duplicate requests.

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Network Behavior

The currency converter adapts to different network conditions:

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Network States

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Normal Access

  • Automatically downloads exchange rates
  • Refreshes data as needed
  • No user prompts required
Source Reference: src/Calculator/Views/UnitConverter.xaml.cs:254-267

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Metered Connection (Opt-In)

  • Prompts user before downloading
  • Shows “Data charges may apply” warning
  • User can click refresh to override and download
  • Preference remembered for session
Source Reference: src/Calculator/Views/UnitConverter.xaml.cs:269-282

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Offline Mode

  • Uses cached exchange rates
  • Shows offline indicator with timestamp
  • Displays link to network settings
  • No automatic refresh attempts
Source Reference: src/Calculator/Views/UnitConverter.xaml.cs:284-288

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Currency Display

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Currency Symbols

Currency symbols are displayed according to regional preferences:
  • Left-side - Symbol before amount (e.g., “$100”)
  • Right-side - Symbol after amount (e.g., “100€”)
The position is determined by your Windows locale settings. Source Reference: src/Calculator/Views/UnitConverter.xaml.cs:54-56

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Exchange Rate Information

The converter displays:
  • Equality Statement - “1 USD = 0.85 EUR”
  • Accessible Equality - Screen-reader friendly version
  • Inverse Rate - Conversion in opposite direction
Source Reference: src/CalcManager/UnitConverter.h:194-195

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Timestamp Display

Shows when exchange rates were last updated:
  • Normal font weight for recent data
  • Bold font weight if data is more than a week old
  • Absolute date/time stamp
Source Reference: src/Calculator/Views/UnitConverter.xaml.cs:336-346

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Data Structure

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Currency Static Data

Each currency contains: 
struct CurrencyStaticData {
    std::wstring countryCode;    // ISO country code
    std::wstring countryName;    // Country name
    std::wstring currencyCode;   // ISO currency code (USD, EUR, etc.)
    std::wstring currencyName;   // Currency name
    std::wstring currencySymbol; // Symbol ($, €, £, etc.)
};
Source Reference: src/CalcManager/UnitConverter.h:143-150

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Currency Ratio

Exchange rate information: 
struct CurrencyRatio {
    double ratio;                      // Exchange rate
    std::wstring sourceCurrencyCode;   // From currency
    std::wstring targetCurrencyCode;   // To currency
};
Source Reference: src/CalcManager/UnitConverter.h:152-157

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Callback Interface

The currency converter uses callbacks to update the UI:
  • CurrencyDataLoadFinished - Notifies when data loading completes
  • CurrencySymbolsCallback - Updates currency symbols
  • CurrencyRatiosCallback - Updates exchange rate display
  • CurrencyTimestampCallback - Updates last refresh time
  • NetworkBehaviorChanged - Handles network state changes
Source Reference: src/CalcManager/UnitConverter.h:166-175

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Loading States

The converter provides visual feedback during operations:

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Progress Indication

  • Progress ring appears after 500ms delay
  • Prevents UI flicker for fast connections
  • Cancels if data loads quickly
Source Reference: src/Calculator/Views/UnitConverter.xaml.cs:348-374

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State Transitions

  1. Unit Not Loaded - Initial state or during refresh
  2. Loading - Progress ring visible
  3. Unit Loaded - Data available, conversion ready
  4. Failed - Error state with retry option
Source Reference: src/Calculator/Views/UnitConverter.xaml.cs:209-228

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Error Handling

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Network Errors

If rate download fails:
  • “Failed to refresh” message displayed
  • Last cached rates still available
  • Retry button enabled
  • Error doesn’t prevent using cached data
Source Reference: src/Calculator/Views/UnitConverter.xaml.cs:330-334

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Cache Failures

If cache is unavailable:
  • Attempts web download immediately
  • Shows loading indicator
  • Falls back to offline mode if both fail

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Async Operations

Currency data loading uses async operations:
  • TryLoadDataFromCacheAsync() - Load from local cache
  • TryLoadDataFromWebAsync() - Download from Bing
  • TryLoadDataFromWebOverrideAsync() - Force download (metered override)
Source Reference: src/CalcManager/UnitConverter.h:198-200

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Privacy & Telemetry

Currency conversion telemetry is disabled in developer builds by default. It can be enabled with the SEND_DIAGNOSTICS build flag.
Source Reference: README.md:58-62

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Common Use Cases

  • Travel planning - Convert home currency to destination currency
  • International shopping - Compare prices across regions
  • Foreign exchange - Calculate exchange rates for transactions
  • Investment tracking - Monitor currency values
  • Business calculations - International pricing and invoicing

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