wxwidgets drag child

wxdrag.cpp

#include <wx/wx.h>
#include <wx/utils.h>

template <class T>
class Movable : public T {
	bool dragging;
	int x,y;
	int height, width;
	int top, left, topScreen, leftScreen;
	wxWindow* parent;
	
	void updateCursorPos(wxMouseEvent& evt) {
		wxPoint mouseOnScreen = wxGetMousePosition();
		
		int nx = mouseOnScreen.x - x,
		 	ny = mouseOnScreen.y - y;
		
		wxPoint position(parent->ScreenToClient(wxPoint( nx, ny )));
		this->Move(position);
	}

protected:
	/*
	 * Attach the event handler manually
	 */
	void ConnectEvents() {
		this->Connect(wxEVT_LEFT_DOWN, wxMouseEventHandler(Movable<T>::onMouseDown));
		this->Connect(wxEVT_LEFT_UP, wxMouseEventHandler(Movable<T>::onMouseUp));
		this->Connect(wxEVT_MOTION, wxMouseEventHandler(Movable<T>::onMove));
	}
	
public:

	/*
	 * Constructor
	 */
	Movable(wxWindow* parent) : T (parent, wxID_ANY, wxT("Drag me around")) {
		Movable::parent = parent;
		ConnectEvents();
		dragging = false;
	}

	/*
	 * Mouse button press
	 */
	void onMouseDown(wxMouseEvent& evt) {
		this->CaptureMouse();
		x = evt.GetX();
		y = evt.GetY();

		parent->GetScreenPosition(&topScreen, &leftScreen);
		dragging=true;
	}
	
	/*
	 * Mouse button release
	 */
	void onMouseUp(wxMouseEvent& evt) {
		this->ReleaseMouse();
		dragging=false;
	}

	/*
	 * Mouse cursor motion
	 */
	void onMove(wxMouseEvent& evt)
	{
		//int newHeight, newWidth;
		wxPoint mouseOnScreen = this->ScreenToClient(wxGetMousePosition());

		this->GetSize(&height, &width);
		this->GetScreenPosition(&top, &left);

		/*
		 * Are we supposed to be dragging our widget around the container?
		 */
		if (dragging) {
			wxSetCursor( wxNullCursor );
			updateCursorPos( evt );
		}
		else {
			this->SetLabel(wxString::Format("%d %d %d %d", mouseOnScreen.x, height, mouseOnScreen.y, width));

			// Change cursor to signify that pointer is on border
			auto cursor = wxNullCursor;
			
			if ((( mouseOnScreen.x > 0 && mouseOnScreen.y > 0 )) 
			&& ((( mouseOnScreen.x < height && mouseOnScreen.y < width )))) {
				// Do nothing.
			}
			else if (mouseOnScreen.x == 0) {
				cursor = wxCURSOR_SIZEWE;
			}
			else if (mouseOnScreen.y == 0) {
				cursor = wxCURSOR_SIZENS;
			}
			
			::wxSetCursor( cursor );
		}
	}
};

class MyFrame : public wxFrame {
	wxPanel* mainPanel = new wxPanel(this, wxID_ANY);
	Movable<wxButton> *btnMove1 = new Movable<wxButton>(this);
	
public:
	MyFrame(wxWindow* ptr, int id, wxString name, wxPoint pos, wxSize size) : wxFrame(ptr,id,name,pos,size) {
		Center();
		Show();
	}
};

class Application: public wxApp {
	MyFrame* frame = new MyFrame(NULL, wxID_ANY,  wxT("Hello World"), wxDefaultPosition, wxSize(640,480));
	virtual bool OnInit();
};

IMPLEMENT_APP(Application)

bool Application::OnInit() {
	return true;
}