Window class not found

ulillillia · 05-07-2009, 07:51 PM

Having adapted my program to using malloc instead of direct allocation, I have this strange, unexpected problem. Without even touching these Windows elements, suddenly, BitBlt stopped working (causing something to appear in the top left of my screen drawn on top of everything, making it impossible to see what I'm doing. I found the cause to be the WindowHandle being 0. Using common diagnostics, the "GetLastError" function, I see that the class is not being found. Why is this? How come, without even changing this content, it suddenly stopped working? The only change I made was that of using malloc (which works as far as I can tell) for my image data, which is irrelevent....

Code:

// Window definitions
HWND WindowHandle; // window handle
WNDCLASSEX WindowClass; // window class

// in the WinMain function, first thing
	WindowClass.cbSize = sizeof(WNDCLASSEX);
	WindowClass.style = CS_HREDRAW | CS_VREDRAW;
	WindowClass.lpfnWndProc = WndProc;
	WindowClass.cbClsExtra = 0;
	WindowClass.cbWndExtra = 0;
	WindowClass.hInstance = hInstance;
	WindowClass.hIcon = LoadIcon(NULL, IDI_APPLICATION);
	WindowClass.hCursor = LoadCursor(NULL, IDC_ARROW);
	WindowClass.hbrBackground = (HBRUSH)GetStockObject(BLACK_BRUSH);
	WindowClass.lpszMenuName = NULL;
	WindowClass.lpszClassName = "MyClass";
	WindowClass.hIconSm = LoadIcon(NULL, IDI_WINLOGO);
	
	// Register the window class
	if (!RegisterClassEx(&WindowClass);)
	{
		DebugTest[19] = (double)GetLastError();
		return 1;
	}
	
	WindowHandle = CreateWindowW("MyClass",
		"Platform Masters 1.0 (development version)",
		WS_OVERLAPPEDWINDOW |
		WS_VISIBLE |
		WS_SYSMENU,
		WindowPos.x, WindowPos.y,
		WindowSize.x, WindowSize.y,
		NULL,
		NULL,
		hInstance,
		NULL);
	
	DebugTest[19] = (double)GetLastError(); // returns 1407 - cannot find class
	
	if (WindowHandle == 0)
	{
		return 0;
	}

DaveH · 05-08-2009, 08:51 AM

The code you posted has errors.

Code:

if (!RegisterClassEx(&WindowClass);)  <<------  ; shouldn't be there

WindowPos and WindowSize are not shown to be defined. When I placed your code in a generated hello world app, I used CW_USEDEFAULT for .x's and 0 for .y's. I also had to change the WinMain so it didn't use the InitInstance and RegisterClass functions that were generated. I also added a DWORD ret for your DebugTest[19], since it also wasn't shown to be defined. The program ran as expected. No errors, therefore the code you posted isn't the problem. (Assuming your positioning variables have valid values and the ; error above was just a typo here, not in your actual code.

tjb · 05-10-2009, 01:06 AM

You're calling CreateWindowW, not CreateWindowA, so your class name parameter should be L"MyClass" (note the L prefix), not "MyClass". Also, although it may not be an issue depending on exactly how you're compiling the file, your "MyClass" in the context of WindowClass.lpszClassName = "MyClass" really should be _T("MyClass") (which expands to "MyClass" or L"MyClass", depending on the UNICODE preprocessor definition).

Read up on CreateWindow. Any literal parameter that is LPTSTR or LPCTSTR should be written as "XXXX" if calling CreateWindowA, L"XXXX" if calling CreateWindowW, or _T("XXXX") if calling CreateWindow (which is just defined to be CreateWindowA or CreateWindowW, depending on UNICODE and/or _UNICODE).

Cactus_Hugger · 05-12-2009, 10:01 PM

Quote:

Read up on CreateWindow. Any literal parameter that is LPTSTR or LPCTSTR should be written as "XXXX" if calling CreateWindowA, L"XXXX" if calling CreateWindowW, or _T("XXXX") if calling CreateWindow (which is just defined to be CreateWindowA or CreateWindowW, depending on UNICODE and/or _UNICODE).

You're on the right track there. But:
LPTSTR, LPCTSTR - _T("XXXX") - Found in structures, mostly.
LPSTR, LPCSTR - "XXXX" - Found in the A versions of the functions, ie, CreateWindowA
LPWSTR, LPCWSTR - L"XXXX" - Found in the W versions of the functions, ie, CreateWindowW

05-07-2009, 07:51 PM	#1
ulillillia Math wizard Join Date: Dec 2006 Location: Minot, ND, USA Posts: 516	Window class not found - why? Having adapted my program to using malloc instead of direct allocation, I have this strange, unexpected problem. Without even touching these Windows elements, suddenly, BitBlt stopped working (causing something to appear in the top left of my screen drawn on top of everything, making it impossible to see what I'm doing. I found the cause to be the WindowHandle being 0. Using common diagnostics, the "GetLastError" function, I see that the class is not being found. Why is this? How come, without even changing this content, it suddenly stopped working? The only change I made was that of using malloc (which works as far as I can tell) for my image data, which is irrelevent.... Code: // Window definitions HWND WindowHandle; // window handle WNDCLASSEX WindowClass; // window class // in the WinMain function, first thing WindowClass.cbSize = sizeof(WNDCLASSEX); WindowClass.style = CS_HREDRAW \| CS_VREDRAW; WindowClass.lpfnWndProc = WndProc; WindowClass.cbClsExtra = 0; WindowClass.cbWndExtra = 0; WindowClass.hInstance = hInstance; WindowClass.hIcon = LoadIcon(NULL, IDI_APPLICATION); WindowClass.hCursor = LoadCursor(NULL, IDC_ARROW); WindowClass.hbrBackground = (HBRUSH)GetStockObject(BLACK_BRUSH); WindowClass.lpszMenuName = NULL; WindowClass.lpszClassName = "MyClass"; WindowClass.hIconSm = LoadIcon(NULL, IDI_WINLOGO); // Register the window class if (!RegisterClassEx(&WindowClass);) { DebugTest[19] = (double)GetLastError(); return 1; } WindowHandle = CreateWindowW("MyClass", "Platform Masters 1.0 (development version)", WS_OVERLAPPEDWINDOW \| WS_VISIBLE \| WS_SYSMENU, WindowPos.x, WindowPos.y, WindowSize.x, WindowSize.y, NULL, NULL, hInstance, NULL); DebugTest[19] = (double)GetLastError(); // returns 1407 - cannot find class if (WindowHandle == 0) { return 0; } __________________ High elevation is the best elevation. The higher, the better the view! My computer: XP Pro SP3, 3.17 GHz C2D CPU, 4 GB DDRII800 RAM (3 GB effective), X-Fi Platinum sound, GeForce 7600 GT, 1920x1440 resolution, 250 GB HDD, Visual C++ 2008 Express
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05-08-2009, 08:51 AM	#2
DaveH Registered User Join Date: Dec 2007 Posts: 146	The code you posted has errors. Code: if (!RegisterClassEx(&WindowClass);) <<------ ; shouldn't be there WindowPos and WindowSize are not shown to be defined. When I placed your code in a generated hello world app, I used CW_USEDEFAULT for .x's and 0 for .y's. I also had to change the WinMain so it didn't use the InitInstance and RegisterClass functions that were generated. I also added a DWORD ret for your DebugTest[19], since it also wasn't shown to be defined. The program ran as expected. No errors, therefore the code you posted isn't the problem. (Assuming your positioning variables have valid values and the ; error above was just a typo here, not in your actual code. Last edited by DaveH; 05-08-2009 at 08:54 AM.
DaveH is offline

05-10-2009, 01:06 AM	#3
tjb Registered User Join Date: Jan 2009 Posts: 31	You're calling CreateWindowW, not CreateWindowA, so your class name parameter should be L"MyClass" (note the L prefix), not "MyClass". Also, although it may not be an issue depending on exactly how you're compiling the file, your "MyClass" in the context of WindowClass.lpszClassName = "MyClass" really should be _T("MyClass") (which expands to "MyClass" or L"MyClass", depending on the UNICODE preprocessor definition). Read up on CreateWindow. Any literal parameter that is LPTSTR or LPCTSTR should be written as "XXXX" if calling CreateWindowA, L"XXXX" if calling CreateWindowW, or _T("XXXX") if calling CreateWindow (which is just defined to be CreateWindowA or CreateWindowW, depending on UNICODE and/or _UNICODE). Last edited by tjb; 05-10-2009 at 01:09 AM.
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