fix(win): Embed manifest in OIIO .exes to enable long path handling

src/cmake/fancy_add_executable.cmake

@@ -44,6 +44,12 @@ macro (fancy_add_executable)
     check_is_enabled (${_target_NAME} _target_NAME_enabled)
     if (_target_NAME_enabled)
         add_executable (${_target_NAME} ${_target_SRC})
+        if (WIN32)
+            # Disable default manifest generation to avoid conflicts.
+            target_link_options(${_target_NAME} PRIVATE "/MANIFEST:NO")
+            # Include Windows resource file, which will in turn embed our exe manifest.
+            target_sources(${_target_NAME} PRIVATE "${PROJECT_SOURCE_DIR}/src/windows/oiio_exe.rc")
+        endif ()
         target_include_directories (${_target_NAME} PRIVATE ${_target_INCLUDE_DIRS})
         target_include_directories (${_target_NAME} SYSTEM PRIVATE ${_target_SYSTEM_INCLUDE_DIRS})
         target_compile_definitions (${_target_NAME} PRIVATE

src/cmake/testing.cmake

@@ -363,13 +363,31 @@ macro (oiio_add_all_tests)
                     ENABLEVAR ENABLE_TARGA
                     IMAGEDIR oiio-images)
     endif()
-    if (NOT WIN32)
+    if (WIN32)
+        if (OIIO_BUILD_TOOLS)
+            # Add test for long path handling if support is enabled at the system level.
+            execute_process (
+                COMMAND ${Python3_EXECUTABLE} "${CMAKE_SOURCE_DIR}/testsuite/windows-long-paths/check_registry.py"
+                RESULT_VARIABLE _reg_check_status
+                OUTPUT_QUIET ERROR_QUIET
+            )
+            if (_reg_check_status EQUAL 0)
+                add_test (NAME windows-long-paths
+                          COMMAND
+                          ${Python3_EXECUTABLE} "${CMAKE_SOURCE_DIR}/testsuite/windows-long-paths/test.py"
+                          --source-root "${CMAKE_SOURCE_DIR}"
+                          --oiiotool-path $<TARGET_FILE:oiiotool>)
+            else ()
+                message (STATUS "Skipping Windows long path test: System-level support is not enabled")
+            endif ()
+        endif ()
+    else ()
         oiio_add_tests (term
                         ENABLEVAR ENABLE_TERM)
         # I just could not get this test to work on Windows CI. The test fails
         # when comparing the output, but the saved artifacts compare just fine
         # on my system. Maybe someone will come back to this.
-        endif ()
+    endif ()
     oiio_add_tests (tiff-suite tiff-depths tiff-misc
                     IMAGEDIR oiio-images/libtiffpic)
     oiio_add_tests (webp

src/windows/oiio_exe.manifest

@@ -0,0 +1,15 @@
+<?xml version="1.0" encoding="UTF-8" standalone="yes"?>
+<assembly xmlns="urn:schemas-microsoft-com:asm.v1" manifestVersion="1.0">
+  <trustInfo xmlns="urn:schemas-microsoft-com:asm.v3">
+    <security>
+      <requestedPrivileges>
+        <requestedExecutionLevel level="asInvoker" uiAccess="false"></requestedExecutionLevel>
+      </requestedPrivileges>
+    </security>
+  </trustInfo>
+  <application xmlns="urn:schemas-microsoft-com:asm.v3">
+    <windowsSettings xmlns:ws2="http://schemas.microsoft.com/SMI/2016/WindowsSettings">
+        <ws2:longPathAware>true</ws2:longPathAware>
+    </windowsSettings>
+  </application>
+</assembly>

src/windows/oiio_exe.rc

@@ -0,0 +1,6 @@
+// Resource script for OIIO EXEs.
+
+// The value is invariant, so should be safe to hardcode, but we could replace
+// 24 with `RT_MANIFEST` by adding `#include "winres.h"` first.
+// Reference: https://learn.microsoft.com/en-us/windows/win32/menurc/user-defined-resource
+1 24 "oiio_exe.manifest"

testsuite/windows-long-paths/check_registry.py

@@ -0,0 +1,36 @@
+"""Helper script to detect system-level long path support on Windows.
+
+Returns 0 if the long path support is enabled in the registry, or 1 otherwise.
+
+Reference: https://learn.microsoft.com/en-us/windows/win32/fileio/maximum-file-path-limitation?tabs=registry#registry-setting-to-enable-long-paths
+"""
+
+# Copyright Contributors to the OpenImageIO project.
+# SPDX-License-Identifier: Apache-2.0
+# https://github.com/AcademySoftwareFoundation/OpenImageIO
+
+import sys
+import winreg
+
+_SUB_KEY = "SYSTEM\\CurrentControlSet\\Control\\FileSystem"
+_VALUE_NAME = "LongPathsEnabled"
+
+
+def main() -> int:
+    try:
+        with winreg.OpenKey(winreg.HKEY_LOCAL_MACHINE, _SUB_KEY) as key:
+            reg_value, value_type = winreg.QueryValueEx(key, _VALUE_NAME)
+    except OSError:
+        # Key does not exist
+        return 1
+
+    # It's vanishingly unlikely that someone would stuff some other value type
+    # in this key, but let's be paranoid.
+    if value_type != winreg.REG_DWORD:
+        return 1
+
+    return int(reg_value != 1)
+
+
+if __name__ == "__main__":
+    sys.exit(main())

testsuite/windows-long-paths/test.py

@@ -0,0 +1,56 @@
+"""Test script for long path support in compiled Windows executables.
+
+This script verifies that `oiiotool` can read paths longer than MAX_PATH (260)
+characters on Windows.
+
+Reference: https://learn.microsoft.com/en-us/windows/win32/fileio/maximum-file-path-limitation
+"""
+
+# Copyright Contributors to the OpenImageIO project.
+# SPDX-License-Identifier: Apache-2.0
+# https://github.com/AcademySoftwareFoundation/OpenImageIO
+
+import argparse
+import os
+import shutil
+import subprocess
+import sys
+import tempfile
+from uuid import uuid4
+
+_WINDOWS_MAX_PATH = 260
+
+
+def main(src_root: str, oiiotool_exe: str) -> int:
+    """
+    Manufactures a long directory path within a temp. directory, copies a test
+    image to it, and ensures `oiiotool` can read it without erroring.
+    """
+    if not os.path.isfile(oiiotool_exe):
+        print(f"ERROR: oiiotool path {oiiotool_exe!r} does not exist")
+        return 1
+
+    test_image = "grid.tif"
+    src_image_path = os.path.join(src_root, "testsuite", "common", test_image)
+
+    with tempfile.TemporaryDirectory() as test_dir:
+        while len(test_dir) < _WINDOWS_MAX_PATH:
+            test_dir = os.path.join(test_dir, str(uuid4()))
+        os.makedirs(test_dir, exist_ok=True)
+
+        shutil.copy(src_image_path, test_dir)
+        test_image_path = os.path.join(test_dir, test_image)
+
+        print("Testing long image path:", test_image_path, flush=True)
+        result = subprocess.call([oiiotool_exe, test_image_path, "--printinfo"])
+
+    return result
+
+
+if __name__ == "__main__":
+    parser = argparse.ArgumentParser(description="Windows long path test")
+    parser.add_argument("--source-root", required=True)
+    parser.add_argument("--oiiotool-path", required=True)
+    args = parser.parse_args()
+
+    sys.exit(main(args.source_root, args.oiiotool_path))