Updated to use Qt6; Created initial structure of the viewer with OpenGL widget

src/qtviewer/IfcViewerWidget.cpp

@@ -0,0 +1,27 @@
+#include "IfcViewerWidget.h"
+
+IfcViewerWidget::IfcViewerWidget(QWidget *parent)
+    : QOpenGLWidget(parent)
+{}
+
+void IfcViewerWidget::initializeGL()
+{
+    // Set up the rendering context, load shaders and other resources, etc.:
+    QOpenGLFunctions *f = QOpenGLContext::currentContext()->functions();
+    f->glClearColor(1.0f, 1.0f, 1.0f, 1.0f);
+}
+
+void IfcViewerWidget::resizeGL(int w, int h)
+{
+    // Update projection matrix and other size related settings:
+    m_projection.setToIdentity();
+    m_projection.perspective(45.0f, w / float(h), 0.01f, 100.0f);
+}
+
+void IfcViewerWidget::paintGL()
+{
+    // Render geometries from the parsed IFC file
+    // Draw the scene:
+    QOpenGLFunctions *f = QOpenGLContext::currentContext()->functions();
+    f->glClear(GL_COLOR_BUFFER_BIT); 
+}