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wxRuby Enum values

The wxWidget library liberally mixes integer constants and enum values for things like IDs, style flags and option flags and such without much consistency.
In previous wxRuby versions these were all mapped to integer constants which had 2 distinct disadvantages.

• loss of scoping
  Integer constants for enum values would all be declared in the enclosing scope for the enum declaration loosing the naming scope which originally existed in C++ (excepting anonymous enums).

• loss of type-safety
  Constants for enum values with identical integer values are indistinguishable from each other.

The wxRuby3 project attempts to provide a solution to that by introducing the Wx::Enum class which is used as a base class for mapping all (named) wxWidget enums to Ruby. The reference documentation for the Wx::Enum class can be found here.

Any named wxWidget enum is mapped to a similarly named (Rubified C++ name) derived Enum class with each enum value defined as a constant of the enum class referencing an instance of the enum class with the corresponding integer value like for example the 'wxSystemFont' enum which is defined in wxRuby as:

module Wx
  class SystemFont < Wx::Enum
  
    # Original equipment manufacturer dependent fixed-pitch font.
    # 
    SYS_OEM_FIXED_FONT = Wx::SystemFont.new(10)
    
    # Windows fixed-pitch (monospaced) font.
    # 
    SYS_ANSI_FIXED_FONT = Wx::SystemFont.new(11)
    
    # Windows variable-pitch (proportional) font.
    # 
    SYS_ANSI_VAR_FONT = Wx::SystemFont.new(12)
    
    # System font.
    # 
    SYS_SYSTEM_FONT = Wx::SystemFont.new(13)
    
    # Device-dependent font.
    # 
    SYS_DEVICE_DEFAULT_FONT = Wx::SystemFont.new(14)
    
    # Default font for user interface objects such as menus and dialog boxes.
    # 
    SYS_DEFAULT_GUI_FONT = Wx::SystemFont.new(17)
    
  end # SystemFont
end

or the 'wxBorder' enum which is defined in wxRuby as:

module Wx
  # Border flags for Wx::Window.
  class Border < Wx::Enum

    # This is different from Wx::Border::BORDER_NONE as by default the controls do have a border.
    # 
    BORDER_DEFAULT = Wx::Border.new(0)

    # 
    # 
    BORDER_NONE = Wx::Border.new(2097152)

    # 
    # 
    BORDER_STATIC = Wx::Border.new(16777216)

    # 
    # 
    BORDER_SIMPLE = Wx::Border.new(33554432)

    # 
    # 
    BORDER_RAISED = Wx::Border.new(67108864)

    # 
    # 
    BORDER_SUNKEN = Wx::Border.new(134217728)

    # 
    # 
    BORDER_DOUBLE = Wx::Border.new(268435456)

    # 
    # 
    BORDER_THEME = Wx::Border.new(268435456)

    # 
    # 
    BORDER_MASK = Wx::Border.new(522190848)

  end # Border
end

Enum instances are interchangeable with integer constants in wxRuby with respect to arithmetic or logical operations. This make it possible to use enum values to construct integer bitflag arguments like:

Wx::TextCtrl.new(pane, Wx::ID_ANY, sample_desc.description, style: Wx::TE_MULTILINE|Wx::TE_READONLY|Wx::BORDER_NONE)

where Wx::ID_ANY is a Wx::StandardID enum instance passed to provide an integer argument value, Wx::TE_MULTILINE and Wx::TE_READONLY are simple integer constants and Wx::BORDER_NONE is a Wx::Border enum instance.

In other cases however enum values can provide just the right kind of type safety where explicit enum values are expected like for example with:

Wx::Font.new(36, Wx::FONTFAMILY_SWISS, Wx::FONTSTYLE_NORMAL, Wx::FONTWEIGHT_NORMAL)

where the Wx::Font constructor definition is:

initialize(pointSize, family, style, weight, underline = false, faceName = Wx::EMPTY_STRING, encoding = Wx::FONTENCODING_DEFAULT) ⇒ Wx::Font

with the following parameter specification:

• pointSize (Integer)
• family (Wx::FontFamily)
• style (Wx::FontStyle)
• weight (Wx::FontWeight)
• underline (true, false) (defaults to: false)
• faceName (String) (defaults to: Wx::EMPTY_STRING)
• encoding (Wx::FontEncoding) (defaults to: Wx::FONTENCODING_DEFAULT)

In this case the constructor explicitly expects specific enum value types for family, style and weigth and providing the integer literal value 74 instead of Wx::FONTFAMILY_SWISS (or any other constant representing the same integer value) will not work (raises an exception) although the integer values for the two are equal.

As you have probably noticed it is not required to use the full naming for an enum instance constant (like Wx::FontFamily::FONTFAMILY_SWISS). All enum value constants are accessible from the naming scope where the enum class to which they belong has been declared.