[render] add WINDOW_MANAGER_ID to all Window Managers

vclib/render/include/vclib/glfw/window_manager.h

@@ -25,8 +25,8 @@
 
 #include "input.h"
 
-// #include <vclib/render/interfaces/event_manager_i.h>
 #include <vclib/render/concepts/renderer.h>
+#include <vclib/render/window_managers.h>
 #include <vclib/space/core/point.h>
 
 #if defined(__linux__)
@@ -83,11 +83,18 @@ class WindowManager
 public:
     /**
      * @brief The ParentType is the type of the parent class. It is used to
-     * initialize the base class (if any). In the GLFW WindowManager, the parent
-     * class is void and it is not managed.
+     * initialize the base class (if any). In the glfw::WindowManager, the
+     * parent class is void and it is not managed.
      */
     using ParentType = void;
 
+    /**
+     * @brief The WINDOW_MANAGER_ID is the ID of the window manager. It is used
+     * to identify the window manager implementation (if necessary) by the
+     * DerivedRenderer class.
+     */
+    static const uint WINDOW_MANAGER_ID = WindowManagerId::GLFW_WINDOW;
+
     WindowManager(ParentType* parent = nullptr) :
             WindowManager("", 1024, 768, parent)
     {

vclib/render/include/vclib/qt/widget_manager.h

@@ -25,8 +25,8 @@
 
 #include "input.h"
 
-//#include <vclib/render/interfaces/event_manager_i.h>
 #include <vclib/render/concepts/renderer.h>
+#include <vclib/render/window_managers.h>
 #include <vclib/space/core/point.h>
 
 #if defined(VCLIB_RENDER_BACKEND_BGFX)
@@ -56,8 +56,20 @@ class WidgetManager :
 #endif
 
 public:
+    /**
+     * @brief The ParentType is the type of the parent class. It is used to
+     * initialize the base class (if any). In the qt::WidgetManager, the parent
+     * class is the QWidget class.
+     */
     using ParentType = QWidget;
 
+    /**
+     * @brief The WINDOW_MANAGER_ID is the ID of the window manager. It is used
+     * to identify the window manager implementation (if necessary) by the
+     * DerivedRenderer class.
+     */
+    static const uint WINDOW_MANAGER_ID = WindowManagerId::QT_WIDGET;
+
     WidgetManager(QWidget* parent = nullptr) : Base(parent)
     {
         static_assert(

vclib/render/include/vclib/render/concepts/window_manager.h

@@ -68,6 +68,14 @@ namespace vcl {
  * (e.g. Qt). If the parent object is not available, the type should be set to
  * `void`.
  *
+ * @par Static constants
+ *
+ * The class must have the following static constants:
+ * - `WINDOW_MANAGER_ID`: The ID of the window manager. It is used to identify
+ * the window manager implementation (if necessary) by the DerivedRenderer
+ * class. It must be a static constant of type `uint`. The value of the constant
+ * must be equal to one of the values of the @ref vcl::WindowManagerId struct.
+ *
  * @par Member functions
  *
  * The class must have the following member functions:
@@ -92,6 +100,8 @@ concept WindowManagerConcept =
         uint u) {
         typename RemoveRef<T>::ParentType;
 
+        { RemoveRef<T>::WINDOW_MANAGER_ID } -> std::same_as<const uint&>;
+
         RemoveRef<T>();
         RemoveRef<T>(pPtr);
         RemoveRef<T>(s, u, u);

vclib/render/include/vclib/render/window_managers.h

@@ -0,0 +1,48 @@
+/*****************************************************************************
+ * VCLib                                                                     *
+ * Visual Computing Library                                                  *
+ *                                                                           *
+ * Copyright(C) 2021-2025                                                    *
+ * Visual Computing Lab                                                      *
+ * ISTI - Italian National Research Council                                  *
+ *                                                                           *
+ * All rights reserved.                                                      *
+ *                                                                           *
+ * This program is free software; you can redistribute it and/or modify      *
+ * it under the terms of the Mozilla Public License Version 2.0 as published *
+ * by the Mozilla Foundation; either version 2 of the License, or            *
+ * (at your option) any later version.                                       *
+ *                                                                           *
+ * This program is distributed in the hope that it will be useful,           *
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of            *
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the              *
+ * Mozilla Public License Version 2.0                                        *
+ * (https://www.mozilla.org/en-US/MPL/2.0/) for more details.                *
+ ****************************************************************************/
+
+#ifndef WINDOW_MANAGERS_H
+#define WINDOW_MANAGERS_H
+
+namespace vcl {
+
+/**
+ * @brief The WindowManagerId struct enumerates the window managers that can be
+ * used to create and manage a window and its events.
+ *
+ * The window managers are identified by an unsigned integer value, that
+ * corresponds to a specific window manager implementation.
+ */
+struct WindowManagerId
+{
+    enum Enum {
+        GLFW_WINDOW,
+        QT_WIDGET,
+        // Additional window managers here
+
+        WINDOW_MANAGERS_NUMBER
+    };
+};
+
+} // namespace vcl
+
+#endif // WINDOW_MANAGERS_H