handing qwidget.winid to DLL in Python -

i have dll, use opengl draw on window. dll window hwmd.

dll:

extern "c" __declspec(dllexport) int init(hwnd hwnd); extern "c" __declspec(dllexport) void resize(hwnd hwnd, int w, int h); extern "c" __declspec(dllexport) void paint(hwnd hwnd); 

the c++ qt application work properly.

#include "windows.h" #include <qapplication> #include <qwidget> #include <qglwidget> #include <qmessagebox> #include <qsplitter> #include <qlibrary>  typedef void (*initprototype)(hwnd); typedef void (*paintprototype)(hwnd); typedef void (*resizeprototype)(hwnd, int, int);  initprototype c_init; paintprototype c_paint; resizeprototype c_resize;  bool load_opengl_library(){     qlibrary lib("engine3d");     lib.load();     c_init = (initprototype)lib.resolve("init");     c_paint = (paintprototype)lib.resolve("paint");     c_resize = (resizeprototype)lib.resolve("resize");     return true; }  class myglwidget: public qglwidget { public:     myglwidget(qwidget *parent = 0): qglwidget(parent){}     void showevent(qshowevent* event){         c_init((hwnd)(this->winid()));     }     void paintevent(qpaintevent* event){         c_paint((hwnd)this->winid());     }     void resizeevent(qresizeevent* event){         c_resize((hwnd)this->winid(), this->width(), this->height());     } };  int main(int argc, char *argv[]) {     qapplication a(argc, argv);     load_opengl_library();     myglwidget w;     w.show();     return a.exec(); } 

but how same in python? program crushes on sending widget.winid().

# coding=utf-8 import ctypes pyqt5 import qtwidgets, qtopengl app = qtwidgets.qapplication([])  e3d = ctypes.cdll(r"engine3d.dll") init = lambda hwnd: e3d.init(hwnd) paint = lambda hwnd: e3d.paint(hwnd) resize = lambda hwnd, w, h: e3d.paint(hwnd, w, h)  class myglwidget(qtopengl.qglwidget):     def __init__(self):         super().__init__()     def showevent(self, ev):         init(self.winid())     def paintevent(self, ev):         paint(self.winid())     def resizeevent(self, ev):         resize(self.winid(), self.width(), self.height())  w = myglwidget() w.show() app.exec_() 

print(self.winid())

it'd easier check having dll, i'll speak out blue. in c++ code got initialization code:

bool load_opengl_library(){     qlibrary lib("engine3d");     lib.load();     c_init = (initprototype)lib.resolve("init");     c_paint = (paintprototype)lib.resolve("paint");     c_resize = (resizeprototype)lib.resolve("resize");     return true; }  ...  int main(int argc, char *argv[]) {     qapplication a(argc, argv);     load_opengl_library();     myglwidget w;     w.show();     return a.exec(); } 

where create engine instance liband using loadmethod in python you're not doing of that:

w = myglwidget() w.show() app.exec_() 

but before creating myglwidget you're not initializing engine c++ counterpart, question is, why not?