Enably QtForPython for Linux (#5667)

- Fix PALification and include Linux for the QtForPython gem
- Add Linux-only module loader for Pyside2 related modules
- Remove (unnecessary) #if !defined(Q_OS_WIN)

Signed-off-by: Steve Pham <82231385+spham-amzn@users.noreply.github.com>

Gems/QtForPython/Code/Source/Platform/Linux/InitializeEmbeddedPyside2.h

@@ -0,0 +1,60 @@
+/*
+ * Copyright (c) Contributors to the Open 3D Engine Project.
+ * For complete copyright and license terms please see the LICENSE at the root of this distribution.
+ *
+ * SPDX-License-Identifier: Apache-2.0 OR MIT
+ *
+ */
+#pragma once
+
+#include <AzCore/Debug/Trace.h>
+#include <dlfcn.h>
+
+namespace QtForPython
+{
+    const char* s_libPythonLibraryFile = "libpython3.7m.so.1.0";
+    const char* s_libPyside2LibraryFile = "libpyside2.abi3.so.5.14";
+    const char* s_libShibokenLibraryFile = "libshiboken2.abi3.so.5.14";
+
+    class InitializeEmbeddedPyside2
+    {
+    public:
+        InitializeEmbeddedPyside2()
+        {
+            m_libPythonLibraryFile = InitializeEmbeddedPyside2::LoadModule(s_libPythonLibraryFile);
+            m_libPyside2LibraryFile = InitializeEmbeddedPyside2::LoadModule(s_libPyside2LibraryFile);
+            m_libShibokenLibraryFile = InitializeEmbeddedPyside2::LoadModule(s_libShibokenLibraryFile);
+        }
+        virtual ~InitializeEmbeddedPyside2()
+        {
+            InitializeEmbeddedPyside2::UnloadModule(m_libShibokenLibraryFile);
+            InitializeEmbeddedPyside2::UnloadModule(m_libPyside2LibraryFile);
+            InitializeEmbeddedPyside2::UnloadModule(m_libPythonLibraryFile);
+        }
+
+    private:
+        static void* LoadModule(const char* moduleToLoad)
+        {
+            void* moduleHandle = dlopen(moduleToLoad, RTLD_NOW | RTLD_GLOBAL);
+            if (!moduleHandle)
+            {
+                const char* loadError = dlerror();
+                AZ_Error("QtForPython", false, "Unable to load python library %s for Pyside2: %s", moduleToLoad,
+                         loadError ? loadError : "Unknown Error");
+            }
+            return moduleHandle;
+        }
+
+        static void UnloadModule(void* moduleHandle)
+        {
+            if (moduleHandle)
+            {
+                dlclose(moduleHandle);
+            }
+        }
+
+        void* m_libPythonLibraryFile;
+        void* m_libPyside2LibraryFile;
+        void* m_libShibokenLibraryFile;
+    };
+} // namespace QtForPython

Gems/QtForPython/Code/Source/Platform/Linux/PAL_linux.cmake

@@ -6,4 +6,4 @@
 #
 #
 
-set(PAL_TRAIT_BUILD_QTFORPYTHON_SUPPORTED FALSE)
+set(PAL_TRAIT_BUILD_QTFORPYTHON_SUPPORTED TRUE)

Gems/QtForPython/Code/Source/Platform/Linux/qtforpython_editor_linux_files.cmake

@@ -0,0 +1,11 @@
+#
+# Copyright (c) Contributors to the Open 3D Engine Project.
+# For complete copyright and license terms please see the LICENSE at the root of this distribution.
+#
+# SPDX-License-Identifier: Apache-2.0 OR MIT
+#
+#
+
+set(FILES
+    InitializeEmbeddedPyside2.h
+)

Gems/QtForPython/Code/Source/Platform/Mac/InitializeEmbeddedPyside2.h

@@ -0,0 +1,18 @@
+/*
+ * Copyright (c) Contributors to the Open 3D Engine Project.
+ * For complete copyright and license terms please see the LICENSE at the root of this distribution.
+ *
+ * SPDX-License-Identifier: Apache-2.0 OR MIT
+ *
+ */
+#pragma once
+
+namespace QtForPython
+{
+    class InitializeEmbeddedPyside2
+    {
+    public:
+        InitializeEmbeddedPyside2() = default;
+        virtual ~InitializeEmbeddedPyside2() = default;
+    };
+} // namespace QtForPython

Gems/QtForPython/Code/Source/Platform/Mac/qtforpython_editor_macos_files.cmake

@@ -0,0 +1,11 @@
+#
+# Copyright (c) Contributors to the Open 3D Engine Project.
+# For complete copyright and license terms please see the LICENSE at the root of this distribution.
+#
+# SPDX-License-Identifier: Apache-2.0 OR MIT
+#
+#
+
+set(FILES
+    InitializeEmbeddedPyside2.h
+)

Gems/QtForPython/Code/Source/Platform/Windows/InitializeEmbeddedPyside2.h

@@ -0,0 +1,18 @@
+/*
+ * Copyright (c) Contributors to the Open 3D Engine Project.
+ * For complete copyright and license terms please see the LICENSE at the root of this distribution.
+ *
+ * SPDX-License-Identifier: Apache-2.0 OR MIT
+ *
+ */
+#pragma once
+
+namespace QtForPython
+{
+    class InitializeEmbeddedPyside2
+    {
+    public:
+        InitializeEmbeddedPyside2() = default;
+        virtual ~InitializeEmbeddedPyside2() = default;
+    };
+} // namespace QtForPython

Gems/QtForPython/Code/Source/Platform/Windows/qtforpython_editor_windows_files.cmake

@@ -0,0 +1,11 @@
+#
+# Copyright (c) Contributors to the Open 3D Engine Project.
+# For complete copyright and license terms please see the LICENSE at the root of this distribution.
+#
+# SPDX-License-Identifier: Apache-2.0 OR MIT
+#
+#
+
+set(FILES
+    InitializeEmbeddedPyside2.h
+)