Add Imath umbrella/config, remove toFloat main().

* Umbrella for Swift import of Imath, ImathConfig since Swift can't
  generate files yet, and remove the main() call in toFloat, though
  we can probably add toFloat as an executableTarget() later on.

src/Imath/Imath.h

@@ -0,0 +1,41 @@
+#ifndef __IMATH_H__
+#define __IMATH_H__
+
+#include <ImathBox.h>
+#include <ImathBoxAlgo.h>
+#include <ImathColor.h>
+#include <ImathColorAlgo.h>
+#include <ImathConfig.h>
+#include <ImathEuler.h>
+#include <ImathExport.h>
+#include <ImathForward.h>
+#include <ImathFrame.h>
+#include <ImathFrustum.h>
+#include <ImathFrustumTest.h>
+#include <ImathFun.h>
+#include <ImathGL.h>
+#include <ImathGLU.h>
+#include <ImathInt64.h>
+#include <ImathInterval.h>
+#include <ImathLine.h>
+#include <ImathLineAlgo.h>
+#include <ImathMath.h>
+#include <ImathMatrix.h>
+#include <ImathMatrixAlgo.h>
+#include <ImathNamespace.h>
+#include <ImathPlane.h>
+#include <ImathPlatform.h>
+#include <ImathQuat.h>
+#include <ImathRandom.h>
+#include <ImathRoots.h>
+#include <ImathShear.h>
+#include <ImathSphere.h>
+#include <ImathTypeTraits.h>
+#include <ImathVec.h>
+#include <ImathVecAlgo.h>
+#include <half.h>
+#include <halfFunction.h>
+#include <halfLimits.h>
+#include <toFloat.h>
+
+#endif // __IMATH_H__

src/Imath/ImathConfig.h

@@ -0,0 +1,171 @@
+// SPDX-License-Identifier: BSD-3-Clause
+// Copyright Contributors to the OpenEXR Project.
+
+// This file is auto-generated by the cmake configure step
+
+#ifndef INCLUDED_IMATH_CONFIG_H
+#define INCLUDED_IMATH_CONFIG_H 1
+
+#pragma once
+
+//
+// Options / configuration based on O.S. / compiler
+//
+
+//
+// Define whether the half-to-float conversion should use the lookup
+// table method. Note that this is overriden by F16C compiler
+// flags. It is also overrided by the IMATH_HALF_NO_LOOKUP_TABLE
+// macro, if defined.
+//
+#define IMATH_HALF_USE_LOOKUP_TABLE
+
+//
+// Define if the target system has support for large
+// stack sizes.
+//
+/* #undef IMATH_HAVE_LARGE_STACK */
+
+//////////////////////
+//
+// C++ namespace configuration / options
+
+// Current (internal) library namepace name and corresponding public
+// client namespaces.
+#define IMATH_INTERNAL_NAMESPACE_CUSTOM 0
+#define IMATH_INTERNAL_NAMESPACE Imath_3_1
+
+
+#define IMATH_NAMESPACE_CUSTOM 0
+#define IMATH_NAMESPACE Imath
+
+
+//
+// Version information
+//
+#define IMATH_VERSION_STRING "3.1.9"
+#define IMATH_PACKAGE_STRING "Imath 3.1.9"
+
+#define IMATH_VERSION_MAJOR 3
+#define IMATH_VERSION_MINOR 1
+#define IMATH_VERSION_PATCH 9
+#define IMATH_VERSION_RELEASE_TYPE ""
+
+#define IMATH_VERSION_HEX ((uint32_t(IMATH_VERSION_MAJOR) << 24) | \
+                             (uint32_t(IMATH_VERSION_MINOR) << 16) | \
+                             (uint32_t(IMATH_VERSION_PATCH) <<  8))
+
+// IMATH_LIB_VERSION is the library API version: SOCURRENT.SOAGE.SOREVISION
+#define IMATH_LIB_VERSION_STRING "29.8.0"
+
+//
+// Code that depends on the v2 ExcMath mechanism of signal handlers
+// that throw exceptions is incompatible with noexcept, since
+// floating-point overflow and underflow can occur in a wide variety
+// of computations within Imath functions now marked with
+// noexcept. Code that needs to accomodate the exception-handling
+// behavior can build with the IMATH_USE_NOEXCEPT off.
+//
+
+#define IMATH_USE_NOEXCEPT 1
+#if IMATH_USE_NOEXCEPT
+#define IMATH_NOEXCEPT noexcept
+#else
+#define IMATH_NOEXCEPT
+#endif
+
+//
+// By default, opt into the interoparability constructors and assignments.
+// If this causes problems, it can be disabled by defining this symbol to
+// be 0 prior to including any Imath headers.
+//
+// If no such definition is found, we enable automatically unless we are
+// using gcc 4.x, which appears to have bugs that prevent the interop
+// templates from compiling correctly.
+//
+#ifndef IMATH_FOREIGN_VECTOR_INTEROP
+#  if defined(__GNUC__) && __GNUC__ == 4 && !defined(__clang__)
+#    define IMATH_FOREIGN_VECTOR_INTEROP 0
+#  else
+#    define IMATH_FOREIGN_VECTOR_INTEROP 1
+#  endif
+#endif
+
+
+//
+// Decorator that makes a function available for both CPU and GPU, when
+// compiling for Cuda.
+//
+#ifdef __CUDACC__
+  #define IMATH_HOSTDEVICE __host__ __device__
+#else
+  #define IMATH_HOSTDEVICE
+#endif
+
+
+//
+// Some compilers define a special intrinsic to use in conditionals that can
+// speed up extremely performance-critical spots if the conditional is
+// usually (or rarely) is true.  You use it by replacing
+//     if (x) ...
+// with
+//     if (IMATH_LIKELY(x)) ...     // if you think x will usually be true
+// or
+//     if (IMATH_UNLIKELY(x)) ...   // if you think x will rarely be true
+//
+// Caveat: Programmers are notoriously bad at guessing this, so it should be
+// used only with thorough benchmarking.
+//
+#if defined(__GNUC__) || defined(__clang__) || defined(__INTEL_COMPILER)
+#    ifdef __cplusplus
+#        define IMATH_LIKELY(x) (__builtin_expect(static_cast<bool>(x), true))
+#        define IMATH_UNLIKELY(x) (__builtin_expect(static_cast<bool>(x), false))
+#    else
+#        define IMATH_LIKELY(x) (__builtin_expect((x), 1))
+#        define IMATH_UNLIKELY(x) (__builtin_expect((x), 0))
+#    endif
+#else
+#    define IMATH_LIKELY(x) (x)
+#    define IMATH_UNLIKELY(x) (x)
+#endif
+
+
+// On modern versions of gcc & clang, __has_attribute can test support for
+// __attribute__((attr)).  Make sure it's safe for other compilers.
+#ifndef __has_attribute
+#    define __has_attribute(x) 0
+#endif
+
+
+//
+// Simple way to mark things as deprecated.
+// When we are sure that C++14 is our true minimum, then we can just
+// directly use [[deprecated(msg)]].
+//
+#if defined(_MSC_VER)
+# define IMATH_DEPRECATED(msg) __declspec(deprecated(msg))
+#elif defined(__cplusplus) && __cplusplus >= 201402L
+# define IMATH_DEPRECATED(msg) [[deprecated(msg)]]
+#elif defined(__GNUC__) || defined(__clang__)
+# define IMATH_DEPRECATED(msg) __attribute__((deprecated(msg)))
+#else
+# define IMATH_DEPRECATED(msg) /* unsupported on this platform */
+#endif
+
+// Whether the user configured the library to have symbol visibility
+// tagged
+#define IMATH_ENABLE_API_VISIBILITY
+
+// MSVC does not do the same visibility attributes, and when we are
+// compiling a static library we won't be in DLL mode, but just don't
+// define these and the export headers will work out
+#if ! defined(_MSC_VER) && defined(IMATH_ENABLE_API_VISIBILITY)
+#  define IMATH_PUBLIC_SYMBOL_ATTRIBUTE __attribute__ ((__visibility__ ("default")))
+#  define IMATH_PRIVATE_SYMBOL_ATTRIBUTE __attribute__ ((__visibility__ ("hidden")))
+// clang differs from gcc and has type visibility which is needed for enums and templates
+#  if __has_attribute(__type_visibility__)
+#    define IMATH_PUBLIC_TYPE_VISIBILITY_ATTRIBUTE __attribute__ ((__type_visibility__ ("default")))
+#  endif
+#endif
+
+#endif // INCLUDED_IMATH_CONFIG_H

src/Imath/toFloat.cpp

@@ -19,6 +19,7 @@
 
 using namespace std;
 
+#if 0
 //---------------------------------------------------
 // Interpret an unsigned short bit pattern as a half,
 // and convert that half to the corresponding float's
@@ -127,3 +128,4 @@ main ()
     cout << "};\n";
     return 0;
 }
+#endif // 0