Fix build error on macOS in Viewer::pollEvents() calling apply methods

[olegded]

Compiling on macOS v10.13.6, using clang version Apple LLVM version 10.0.0 (clang-1000.11.45.5)

There is a compiler error in all apply()-methods in Viewer::pollEvents() dealing with enum classes:

In file included from /Users/oleg/dev/osg-vulkan/vsg/src/src/vsg/viewer/Viewer.cpp:13:
In file included from /Users/oleg/dev/osg-vulkan/vsg/src/include/vsg/viewer/Viewer.h:15:
In file included from /Users/oleg/dev/osg-vulkan/vsg/src/include/vsg/viewer/Window.h:17:
In file included from /Users/oleg/dev/osg-vulkan/vsg/src/include/vsg/ui/UIEvent.h:15:
In file included from /Users/oleg/dev/osg-vulkan/vsg/src/include/vsg/core/Inherit.h:15:
In file included from /Users/oleg/dev/osg-vulkan/vsg/src/include/vsg/core/Allocator.h:20:
In file included from /Users/oleg/dev/osg-vulkan/vsg/src/include/vsg/io/stream.h:20:
In file included from /Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/include/c++/v1/istream:163:
/Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/include/c++/v1/ostream:208:20: note: candidate function
    basic_ostream& operator<<(unsigned short __n);
                   ^
/Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/include/c++/v1/ostream:209:20: note: candidate function
    basic_ostream& operator<<(int __n);
                   ^
/Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/include/c++/v1/ostream:206:20: note: candidate function
    basic_ostream& operator<<(bool __n);
                   ^
/Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/include/c++/v1/ostream:207:20: note: candidate function
    basic_ostream& operator<<(short __n);
                   ^
/Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/include/c++/v1/ostream:210:20: note: candidate function
    basic_ostream& operator<<(unsigned int __n);
                   ^
/Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/include/c++/v1/ostream:211:20: note: candidate function
    basic_ostream& operator<<(long __n);
                   ^
/Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/include/c++/v1/ostream:212:20: note: candidate function
    basic_ostream& operator<<(unsigned long __n);
                   ^
/Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/include/c++/v1/ostream:213:20: note: candidate function
    basic_ostream& operator<<(long long __n);
                   ^
/Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/include/c++/v1/ostream:214:20: note: candidate function
    basic_ostream& operator<<(unsigned long long __n);
                   ^
/Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/include/c++/v1/ostream:215:20: note: candidate function
    basic_ostream& operator<<(float __f);
                   ^
/Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/include/c++/v1/ostream:216:20: note: candidate function
    basic_ostream& operator<<(double __f);
                   ^
/Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/include/c++/v1/ostream:217:20: note: candidate function
    basic_ostream& operator<<(long double __f);
                   ^
/Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/include/c++/v1/ostream:788:1: note: candidate function [with _Traits = std::__1::char_traits<char>]
operator<<(basic_ostream<char, _Traits>& __os, char __c)
^
/Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/include/c++/v1/ostream:755:1: note: candidate function [with _CharT = char, _Traits = std::__1::char_traits<char>]
operator<<(basic_ostream<_CharT, _Traits>& __os, char __cn)
^
/Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/include/c++/v1/ostream:795:1: note: candidate function [with _Traits = std::__1::char_traits<char>]
operator<<(basic_ostream<char, _Traits>& __os, signed char __c)
^
/Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/include/c++/v1/ostream:802:1: note: candidate function [with _Traits = std::__1::char_traits<char>]
operator<<(basic_ostream<char, _Traits>& __os, unsigned char __c)

Possible solutions:

1. This proposed change. However, I'm not sure about header file where to define the operator<<. in UIEvent.h or new header file?
2. Defining same method for KeySymbol in KeyEvent.h and ButtonMask in PointerEvent.h, e.g.

std::ostream& operator<<(std::ostream& os, const ButtonMask& obj)
{
    os << static_cast<std::underlying_type<ButtonMask>::type>(obj);
    return os;
}

3. Calling static_cast in corresponding apply() methods

Pull Request Template

Description

Please include a summary of the change and which issue is fixed. Please also include relevant motivation and context. List any dependencies that are required for this change.

Fixes # (issue)

Type of change

Please delete options that are not relevant.

• Bug fix (non-breaking change which fixes an issue)

How Has This Been Tested?

Executed sample programs on macOS

Checklist:

• My code follows the style guidelines of this project
• I have performed a self-review of my own code
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation
• My changes generate no new warnings
• I have added tests that prove my fix is effective or that my feature works
• New and existing unit tests pass locally with my changes
• Any dependent changes have been merged and published in downstream modules

[robertosfield]

Tomorrow I will do a clang build under Linux to see if I can recreate the compile error.

So far I have been putting in the << and >> operator implementations into include/vsg/io/stream.h.

FYI, The actual usage in Viewer::pollEvents() is currently for development/debugging purposes and will disappear once the platform specific Window implementations are complete.

[vsg-dev]

I tried clang under Linux and it failed as well. I have merged you change as it, but then moved the enum << operator into include/vsg/io/steam.h to make it available for a wider range of uses.