Eli Samuel Eli Samuel - 3 months ago 12
C++ Question

Failed CreateWindowEx. How do I get my window (with the button) to actually pop up for once?

I can only assume most of this works because I can't get past the CreateWindowEx check.
If someone would double check all of my fun button code that would be great too.

#include <windows.h>
#include <tchar.h> //I was told I needed this line but I don't believe I do.
#define ID_BTNENCRYPT 0

const char g_szClassName[] = "MyWindowClass";

HWND button;

LRESULT CALLBACK WndProc(HWND hwnd, UINT msg, WPARAM wParam, LPARAM lParam) {
switch(msg) { //Fun button stuff
case WM_CREATE: {
button = CreateWindow("button",
"Encrypt Message",
WS_VISIBLE | WS_CHILD | BS_DEFPUSHBUTTON,
450, 620, 200, 30,
hwnd, (HMENU) ID_BTNENCRYPT, GetModuleHandle(NULL), NULL);

break;
}
case WM_COMMAND: { //More fun button stuff
switch (LOWORD(wParam)){
case ID_BTNENCRYPT: {
::MessageBox(hwnd, "This will be your message once I get my $h!t together", "Encrypted Message", MB_OK);
}
}
break;
}
case WM_CLOSE:
DestroyWindow(hwnd);
break;
case WM_DESTROY:
PostQuitMessage(0);
break;
default:
DefWindowProc(hwnd, msg, wParam, lParam);

}

return 0;
}

int WINAPI WinMain(HINSTANCE hInstance, HINSTANCE hPrevInstance, LPSTR lpCmdLine, int nCmdShow) {
FreeConsole();

WNDCLASSEX wc;
HWND hwnd;
MSG Msg;

wc.cbSize = sizeof(WNDCLASSEX);
wc.style = 0;
wc.lpfnWndProc = WndProc;
wc.cbClsExtra = 0;
wc.cbWndExtra = 0;
wc.hInstance = hInstance;
wc.hIcon = LoadIcon(NULL, IDI_APPLICATION);
wc.hIconSm = LoadIcon(NULL, IDI_APPLICATION);
wc.hCursor = LoadCursor(NULL, IDC_ARROW);
wc.hbrBackground = (HBRUSH) (COLOR_WINDOW + 1);
wc.lpszMenuName = NULL;
wc.lpszClassName = g_szClassName;
if (!RegisterClassEx(&wc)) {
::MessageBox(NULL, "Window Registration Status: Hopelessly F***ed", "", MB_OK);
return 0;
} //No apparent error in Window Registration


Here's where I need help

hwnd = CreateWindowEx(
WS_EX_CLIENTEDGE,
g_szClassName,
"Great Window",
WS_OVERLAPPEDWINDOW,
300, 300,
350, 350,
NULL, NULL, hInstance, NULL);
if (hwnd == NULL) {
::MessageBox(NULL,"Window Creation Status: Gone to $h!t", "", MB_OK);
}


I unfortunately get the error message that yes, my window creation has failed.

ShowWindow(hwnd, nCmdShow); //Just the end of my code from here on out.
UpdateWindow(hwnd); //Hopefully there aren't any fatal errors.

while(GetMessage(&Msg, NULL, 0, 0) > 0) {
TranslateMessage(&Msg);
DispatchMessage(&Msg);
}

return Msg.wParam;
}

Answer

Your WndProc() is not returning the return value of DefWindowProc() for unhandled messages. There is a missing return statement, so you end up falling to return 0 for all messages. When WM_NCCREATE returns 0, CreateWindowEx() fails:

If an application processes this message, it should return TRUE to continue creation of the window. If the application returns FALSE, the CreateWindow or CreateWindowEx function will return a NULL handle.

You need to change this:

default:
    DefWindowProc(hwnd, msg, wParam, lParam);

To this:

default:
    return DefWindowProc(hwnd, msg, wParam, lParam);
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