[cpp] Add Qt Desginer widget plugin examples

cpp/qt/designer-plugin-collection/widgetplugin.cpp

@@ -0,0 +1,52 @@
+/*##############################################################################
+## Author: Shaun Reed                                                         ##
+## Legal: All Content (c) 2022 Shaun Reed, all rights reserved                ##
+## About: Example of a generic Qt Designer widget plugin                      ##
+##                                                                            ##
+## Contact: shaunrd0@gmail.com  | URL: www.shaunreed.com | GitHub: shaunrd0   ##
+################################################################################
+*/
+
+#include "widgetplugin.h"
+#include "textview.h"
+
+#include <QtPlugin>
+#include <utility>
+
+WidgetPlugin::WidgetPlugin(QString group, QString name,
+                           WidgetPlugin::Factory factory)
+    : m_group(std::move(group)), m_name(std::move(name)),
+      m_includeFile(name + ".h"), m_factory(std::move(factory)) {}
+
+WidgetPlugin::WidgetPlugin(QString group, QString name, QString include,
+                           WidgetPlugin::Factory factory)
+    : m_group(std::move(group)), m_name(std::move(name)),
+      m_includeFile(std::move(include)), m_factory(std::move(factory)) {}
+
+QString WidgetPlugin::toolTip() const { return {}; }
+
+QString WidgetPlugin::whatsThis() const { return {}; }
+
+QIcon WidgetPlugin::icon() const { return {}; }
+
+bool WidgetPlugin::isContainer() const { return false; }
+
+QString WidgetPlugin::group() const { return m_group; }
+
+QString WidgetPlugin::name() const { return m_name; }
+
+// TODO: The generated UI headers do not use this member appropriately.
+QString WidgetPlugin::includeFile() const { return m_includeFile; }
+
+QWidget *WidgetPlugin::createWidget(QWidget *parent) {
+  return m_factory(parent);
+}
+
+bool WidgetPlugin::isInitialized() const { return m_initialized; }
+
+void WidgetPlugin::initialize(QDesignerFormEditorInterface *) {
+  if (m_initialized)
+    return;
+
+  m_initialized = true;
+}