Revert "Fix several Qt deprecation warnings (fstl-app#67)"

This reverts commit 18e0e59.

CMakeLists.txt

@@ -52,7 +52,7 @@ set(Icon_Resource exe/fstl.rc)
 set(OpenGL_GL_PREFERENCE GLVND)
 
 #find required packages. 
-find_package(Qt5 5.14 REQUIRED COMPONENTS Core Gui Widgets OpenGL)
+find_package(Qt5 REQUIRED COMPONENTS Core Gui Widgets OpenGL)
 find_package(OpenGL REQUIRED)
 find_package(Threads REQUIRED)
 

src/canvas.cpp

@@ -278,23 +278,23 @@ void Canvas::wheelEvent(QWheelEvent *event)
 {
     // Find GL position before the zoom operation
     // (to zoom about mouse cursor)
-    auto p = event->position();
+    auto p = event->pos();
     QVector3D v(1 - p.x() / (0.5*width()),
                 p.y() / (0.5*height()) - 1, 0);
     QVector3D a = transform_matrix().inverted() *
                   view_matrix().inverted() * v;
 
-    if (event->angleDelta().y() < 0)
+    if (event->delta() < 0)
     {
-        for (int i=0; i > event->angleDelta().y(); --i)
+        for (int i=0; i > event->delta(); --i)
             if (invertZoom)
                 zoom /= 1.001;
             else 
                 zoom *= 1.001;
     }
-    else if (event->angleDelta().y() > 0)
+    else if (event->delta() > 0)
     {
-        for (int i=0; i < event->angleDelta().y(); ++i)
+        for (int i=0; i < event->delta(); ++i) 
             if (invertZoom) 
                 zoom *= 1.001;
             else 

src/window.cpp

@@ -466,7 +466,7 @@ void Window::build_folder_file_list()
 QPair<QString, QString> Window::get_file_neighbors()
 {
     if (current_file.isEmpty()) {
-        return QPair<QString, QString>(QString(), QString());
+        return QPair<QString, QString>(QString::null, QString::null);
     }
 
     build_folder_file_list();
@@ -476,8 +476,8 @@ QPair<QString, QString> Window::get_file_neighbors()
     QString current_dir = fileInfo.absoluteDir().absolutePath();
     QString current_name = fileInfo.fileName();
 
-    QString prev = QString();
-    QString next = QString();
+    QString prev = QString::null;
+    QString next = QString::null;
 
     QListIterator<QString> fileIterator(lookup_folder_files);
     while (fileIterator.hasNext()) {