StandardCalculatorViewModel - Windows Calculator

Overview

The StandardCalculatorViewModel class manages calculator operations for Standard, Scientific, and Programmer modes. It handles expression evaluation, memory operations, number base conversions, and provides data binding for UI elements. Namespace: CalculatorApp.ViewModel Implements: Windows::UI::Xaml::Data::INotifyPropertyChanged Declared in: StandardCalculatorViewModel.h:40

Observable Properties

The ViewModel uses property macros for automatic change notification. Properties are defined using:

OBSERVABLE_PROPERTY_RW(type, name) - Read-write with change notification
OBSERVABLE_PROPERTY_R(type, name) - Read-only with private setter
OBSERVABLE_NAMED_PROPERTY_R(type, name) - Read-only with static property name

Display Properties

DisplayValue

OBSERVABLE_PROPERTY_RW(Platform::String^, DisplayValue);

The primary display value shown to the user.

ExpressionTokens

OBSERVABLE_PROPERTY_R(
    Windows::Foundation::Collections::IObservableVector<Common::DisplayExpressionToken^>^,
    ExpressionTokens
);

Collection of tokens representing the current expression.

IsInError

OBSERVABLE_NAMED_PROPERTY_R(bool, IsInError);

Indicates whether the calculator is in an error state (e.g., division by zero).

OpenParenthesisCount

OBSERVABLE_PROPERTY_R(unsigned int, OpenParenthesisCount);

Number of unclosed opening parentheses in the current expression.

Programmer Mode Properties

DecimalDisplayValue

OBSERVABLE_PROPERTY_R(Platform::String^, DecimalDisplayValue);

Display value in decimal (base 10) format.

HexDisplayValue

OBSERVABLE_PROPERTY_R(Platform::String^, HexDisplayValue);

Display value in hexadecimal (base 16) format.

OctalDisplayValue

OBSERVABLE_PROPERTY_R(Platform::String^, OctalDisplayValue);

Display value in octal (base 8) format.

BinaryDisplayValue

OBSERVABLE_NAMED_PROPERTY_R(Platform::String^, BinaryDisplayValue);

Display value in binary (base 2) format.

BinaryDigits

OBSERVABLE_NAMED_PROPERTY_R(
    Windows::Foundation::Collections::IVector<bool>^,
    BinaryDigits
);

Collection of individual binary digits for bit-flip operations.

CurrentRadixType

OBSERVABLE_PROPERTY_R(CalculatorApp::ViewModel::Common::NumberBase, CurrentRadixType);

Current number base (Decimal, Hexadecimal, Octal, or Binary).

IsBinaryBitFlippingEnabled

OBSERVABLE_PROPERTY_R(bool, IsBinaryBitFlippingEnabled);

Indicates whether bit-flipping mode is active in Programmer mode.

AreProgrammerRadixOperatorsVisible

OBSERVABLE_PROPERTY_R(bool, AreProgrammerRadixOperatorsVisible);

Controls visibility of radix operators (AND, OR, XOR, etc.) in Programmer mode.

Button State Properties

IsBinaryOperatorEnabled

OBSERVABLE_PROPERTY_R(bool, IsBinaryOperatorEnabled);

Enables/disables binary operators (+, -, *, /, etc.).

IsUnaryOperatorEnabled

OBSERVABLE_PROPERTY_R(bool, IsUnaryOperatorEnabled);

Enables/disables unary operators (sin, cos, sqrt, etc.).

IsNegateEnabled

OBSERVABLE_PROPERTY_R(bool, IsNegateEnabled);

Enables/disables the negate (+/-) button.

IsDecimalEnabled

OBSERVABLE_PROPERTY_RW(bool, IsDecimalEnabled);

Enables/disables the decimal point button.

AreHEXButtonsEnabled

OBSERVABLE_PROPERTY_R(bool, AreHEXButtonsEnabled);

Enables/disables hexadecimal letter buttons (A-F) in Programmer mode.

Memory Properties

MemorizedNumbers

OBSERVABLE_PROPERTY_R(
    Windows::Foundation::Collections::IVector<MemoryItemViewModel^>^,
    MemorizedNumbers
);

Collection of values stored in memory.

IsMemoryEmpty

OBSERVABLE_NAMED_PROPERTY_RW(bool, IsMemoryEmpty);

Indicates whether memory is empty.

History

HistoryVM

OBSERVABLE_PROPERTY_R(HistoryViewModel^, HistoryVM);

ViewModel for calculation history.

Accessibility Properties

CalculationResultAutomationName

OBSERVABLE_PROPERTY_R(Platform::String^, CalculationResultAutomationName);

Automation/narrator text for the calculation result.

CalculationExpressionAutomationName

OBSERVABLE_PROPERTY_R(Platform::String^, CalculationExpressionAutomationName);

Automation/narrator text for the expression.

Announcement

OBSERVABLE_PROPERTY_R(
    CalculatorApp::ViewModel::Common::Automation::NarratorAnnouncement^,
    Announcement
);

Narrator announcements for screen reader accessibility.

Mode Properties

These properties determine the active calculator mode:

property bool IsStandard { bool get(); void set(bool value); }
property bool IsScientific { bool get(); void set(bool value); }
property bool IsProgrammer { bool get(); void set(bool value); }

Setting one to true automatically sets the others to false.

IsBitFlipChecked

property bool IsBitFlipChecked { bool get(); void set(bool value); }

Toggles bit-flipping mode in Programmer calculator.

ValueBitLength

property CalculatorApp::ViewModel::Common::BitLength ValueBitLength {
    CalculatorApp::ViewModel::Common::BitLength get();
    void set(CalculatorApp::ViewModel::Common::BitLength value);
}

Sets the bit length for Programmer mode (QWORD, DWORD, WORD, BYTE).

Always-on-Top

IsAlwaysOnTop

OBSERVABLE_PROPERTY_RW(bool, IsAlwaysOnTop);

Indicates whether the calculator is in Always-on-Top mode.

Commands

Commands are defined using the COMMAND_FOR_METHOD macro:

ButtonPressed

COMMAND_FOR_METHOD(ButtonPressed, StandardCalculatorViewModel::OnButtonPressed);

Handles all calculator button presses. Parameter: Platform::Object^ - Button identifier

CopyCommand

COMMAND_FOR_METHOD(CopyCommand, StandardCalculatorViewModel::OnCopyCommand);

Copies the current result to the clipboard.

PasteCommand

COMMAND_FOR_METHOD(PasteCommand, StandardCalculatorViewModel::OnPasteCommand);

Pastes from the clipboard into the calculator.

Memory Commands

COMMAND_FOR_METHOD(MemoryAdd, StandardCalculatorViewModel::OnMemoryAdd);
COMMAND_FOR_METHOD(MemorySubtract, StandardCalculatorViewModel::OnMemorySubtract);
COMMAND_FOR_METHOD(MemoryItemPressed, StandardCalculatorViewModel::OnMemoryItemPressed);
COMMAND_FOR_METHOD(ClearMemoryCommand, StandardCalculatorViewModel::OnClearMemoryCommand);

Handle memory operations (M+, M-, memory recall, memory clear).

Key Methods

SetCalculatorType

void SetCalculatorType(CalculatorApp::ViewModel::Common::ViewMode targetState);

Switches between Standard, Scientific, and Programmer modes.

UpdateOperand

void UpdateOperand(int pos, Platform::String^ text);

Updates the operand at the specified position.

SwitchProgrammerModeBase

void SwitchProgrammerModeBase(CalculatorApp::ViewModel::Common::NumberBase calculatorBase);

Switches between number bases in Programmer mode (DEC, HEX, OCT, BIN).

FtoEButtonToggled

void FtoEButtonToggled();

Toggles scientific notation (F-E) mode.

OnPaste

void OnPaste(Platform::String^ pastedString);

Processes pasted text as calculator input.

SelectHistoryItem

void SelectHistoryItem(HistoryItemViewModel^ item);

Loads a calculation from history.

SetPrecision

void SetPrecision(int32_t precision);

Sets the display precision for decimal values.

Property Macro Usage Examples

Read-Write Observable Property

OBSERVABLE_PROPERTY_RW(Platform::String^, DisplayValue);

Expands to:

property Platform::String^ DisplayValue
{
    Platform::String^ get() { return m_DisplayValue; }
    void set(Platform::String^ value)
    {
        if (m_DisplayValue != value)
        {
            m_DisplayValue = value;
            RaisePropertyChanged(L"DisplayValue");
        }
    }
}
private:
    Platform::String^ m_DisplayValue;
public:

Read-Only Observable Property

OBSERVABLE_PROPERTY_R(bool, IsInError);

Expands to a public getter with a private setter that raises property changed events.

Command Definition

COMMAND_FOR_METHOD(ButtonPressed, StandardCalculatorViewModel::OnButtonPressed);

Expands to:

property Windows::UI::Xaml::Input::ICommand^ ButtonPressed
{
    Windows::UI::Xaml::Input::ICommand^ get()
    {
        if (!donotuse_ButtonPressed)
        {
            donotuse_ButtonPressed = ref new DelegateCommand(
                MakeDelegateCommandHandler(this, &StandardCalculatorViewModel::OnButtonPressed)
            );
        }
        return donotuse_ButtonPressed;
    }
}

INotifyPropertyChanged Implementation

The ViewModel uses the OBSERVABLE_OBJECT_CALLBACK macro:

OBSERVABLE_OBJECT_CALLBACK(OnPropertyChanged);

This generates:

virtual event Windows::UI::Xaml::Data::PropertyChangedEventHandler^ PropertyChanged;
internal:
void RaisePropertyChanged(Platform::String^ p)
{
    PropertyChanged(this, ref new Windows::UI::Xaml::Data::PropertyChangedEventArgs(p));
    OnPropertyChanged(p);
}

The OnPropertyChanged callback is invoked for every property change, allowing custom logic.

Usage Example

// Create calculator ViewModel
auto calcVM = ref new StandardCalculatorViewModel();

// Set to Scientific mode
calcVM->IsScientific = true;

// Simulate button press
calcVM->ButtonPressed->Execute(NumbersAndOperatorsEnum::Num5);

// Copy result
calcVM->CopyCommand->Execute(nullptr);

// Access display value
Platform::String^ result = calcVM->DisplayValue;

// Programmer mode example
calcVM->IsProgrammer = true;
calcVM->SwitchProgrammerModeBase(NumberBase::HexBase);
Platform::String^ hexValue = calcVM->HexDisplayValue;

// Enable bit flipping
calcVM->IsBitFlipChecked = true;
auto binaryDigits = calcVM->BinaryDigits;

Core Components

ViewModels

Unit Conversion

Graphing

​Overview

​Observable Properties

​Display Properties

​DisplayValue

​ExpressionTokens

​IsInError

​OpenParenthesisCount

​Programmer Mode Properties

​DecimalDisplayValue

​HexDisplayValue

​OctalDisplayValue

​BinaryDisplayValue

​BinaryDigits

​CurrentRadixType

​IsBinaryBitFlippingEnabled

​AreProgrammerRadixOperatorsVisible

​Button State Properties

​IsBinaryOperatorEnabled

​IsUnaryOperatorEnabled

​IsNegateEnabled

​IsDecimalEnabled

​AreHEXButtonsEnabled

​Memory Properties

​MemorizedNumbers

​IsMemoryEmpty

​History

​HistoryVM

​Accessibility Properties

​CalculationResultAutomationName

​CalculationExpressionAutomationName

​Announcement

​Mode Properties

​IsBitFlipChecked

​ValueBitLength

​Always-on-Top

​IsAlwaysOnTop

​Commands

​ButtonPressed

​CopyCommand

​PasteCommand

​Memory Commands

​Key Methods

​SetCalculatorType

​UpdateOperand

​SwitchProgrammerModeBase

​FtoEButtonToggled

​OnPaste

​SelectHistoryItem

​SetPrecision

​Property Macro Usage Examples

​Read-Write Observable Property

​Read-Only Observable Property

​Command Definition

​INotifyPropertyChanged Implementation

​Usage Example

​See Also

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