USD/Ctest: Add basic USD-Imaging test.

This adds a basic unit test to check USD has been correctly
build with imaging components to support building both with
the old and new libs, it automatically adds the test when it
detects a library with imaging enabled. (platform devs will
have to pay attention it runs the test to validate the libs
build correctly)

For future use in the code it also defines a USD_HAS_IMAGING
define one could check if we're building against an USD lib
that has it (just because we build/ship with it, doesn't
mean downstream builds will ship with it, so we'll have
to be a little pro-active there)

Reviewed By: sybren

Differential Revision:https://developer.blender.org/D14456

1 files changed, 20 insertions, 0 deletions

diff --git a/source/blender/io/usd/tests/usd_tests_common.h b/source/blender/io/usd/tests/usd_tests_common.h
new file mode 100644
index 00000000000..b298a253ddc
--- /dev/null
+++ b/source/blender/io/usd/tests/usd_tests_common.h
@@ -0,0 +1,20 @@
+/* SPDX-License-Identifier: GPL-2.0-or-later
+ * Copyright 2022 Blender Foundation. All rights reserved. */
+#pragma once
+
+#include <string>
+
+namespace blender::io::usd {
+
+/* Calls the function to load the USD plugins from the
+ * USD data directory under the Blender bin directory
+ * that was supplied as the --test-release-dir flag to ctest.
+ * Thus function must be called before instantiating a USD
+ * stage to avoid errors.  The returned string is the path to
+ * the USD data files directory from which the plugins were
+ * loaded.  If the USD data files directory can't be determined,
+ * plugin registration is skipped and the empty string is
+ * returned. */
+std::string register_usd_plugins_for_tests();
+
+}  // namespace blender::io::usd