SDL2 / wxWidgets SDL_CreateWindowFrom - c++

Question

I have spent the last few days trying to embed an SDL2 display into wxWidgets but failing miserably. OK, here is what I have so far...
First a little detail:
wxWidgets version: 3.1 | SDL version 2.0.4 | OS: Fedora 23 | g++ 5.3.1
I have searched Google but cannot find much up-to-date information. What I have found suggests that I should use SDL_CreateWindowFrom() and then link it to a wxPanel or wxStaticBitmap.
I have written test code which implements a simple wxFrame and initialises SDL2, the code compiles fine but hangs when run.I am new to SDL2 and so would be grateful if somebody would take a look at my code and see what I am doing wrong. I'm obviously misunderstanding something here so any help would be appreciated.
The following code is a simplified block which highlights my problem.
main.h
#include <wx/wx.h>
#include <SDL2/SDL.h>
class TestApp : public wxApp
{
public:
virtual bool OnInit();
};
main.cpp
wxIMPLEMENT_APP_NO_MAIN(TestApp);
// Initialise SDL before WX-Widgets and GTK3
int main(int argc, char** argv)
{
// Initialise SDL and Error Check
if (SDL_Init(SDL_INIT_VIDEO) < 0) {
std::cerr << "SDL Initialisation Error\n\n";
}
return wxEntry(argc, argv);
}
// WX-WIDGETS ENTRY POINT: Handover control to WX-Widgets
bool TestApp::OnInit()
{
UI_Frame *frame = new UI_Frame("SDL Playing with wxWidgets");
frame->Show(true);
return true;
}
TestApp.h
class UI_Frame : public wxFrame
{
public:
UI_Frame(const wxString& title);
private:
wxDECLARE_EVENT_TABLE();
};
And finally, the method which handles SDL and wxFrame
TestApp.cpp
wxBEGIN_EVENT_TABLE(UI_Frame, wxFrame)
wxEND_EVENT_TABLE()
UI_Frame::UI_Frame(const wxString& title) : wxFrame(NULL, wxID_ANY, title)
{
this->SetSize(1024, 768);
wxBoxSizer* topSizer;
topSizer = new wxBoxSizer(wxVERTICAL);
wxPanel *panel = new wxPanel(this, wxID_ANY, wxDefaultPosition, wxDefaultSize, wxTAB_TRAVERSAL);
topSizer->Add(panel, 1, wxEXPAND | wxALL, 5);
/*******************************************************
*
* SDL Specific Stuff
*
******************************************************/
SDL_Window *sdl_window = nullptr;
SDL_Renderer *renderer = nullptr;
// SDL: Create Embedded Window in wxWidgets
sdl_window = SDL_CreateWindowFrom((void *) panel->GetHandle());
if (sdl_window == NULL) {
std::cerr << "SDL NULL Pointer ERROR";
return;
}
// *** This line causes the application to hang ***
renderer = SDL_CreateRenderer(sdl_window, -1, SDL_RENDERER_ACCELERATED);
if (renderer == NULL) {
fprintf(stderr, "SDL: failed to create renderer: %s\n", SDL_GetError());
}
}