# OpenGL GL_INVALID_OP in fullscreen mode only

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I've had a simple game working fine, and have had no problems until I decided to switch it over to fullscreen mode. Unfortunately once I enable fullscreen mode I am starting to receive GL_INVALID_OPERATION errors every time I check glGetError. This doesn't happen in windowed mode, and I'm trying to understand what might be causing this to happen. The window goes into fullscreen mode just fine, and actually partially works, all of my fullscreen background quads are rendered and some of my background shaders are executing properly, but none of my meshes are appearing. So I know that OpenGL is functioning to some extent. Anyway that is all anecdotal, just really trying to figure out why I'm getting these errors. I'll paste my startup code and see if anyone notices anything.
int WINAPI WinMain(HINSTANCE hInstance, HINSTANCE hPrevInstance, LPSTR lpCmdLine, int nShowCmd)
{
WNDCLASSEX windowClass;		// window class
HWND	   hwnd;			// window handle
MSG		   msg;				// message
RECT	   windowRect;

windowRect.left=(long)0;						// Set Left Value To 0
windowRect.right=(long)WINDOWWIDTH;	// Set Right Value To Requested Width
windowRect.top=(long)0;							// Set Top Value To 0
windowRect.bottom=(long)WINDOWHEIGHT;	// Set Bottom Value To Requested Height

// fill out the window class structure
windowClass.cbSize			= sizeof(WNDCLASSEX);
windowClass.style			= CS_HREDRAW | CS_VREDRAW | CS_OWNDC;
windowClass.lpfnWndProc		= MainWindowProc;
windowClass.cbClsExtra		= 0;
windowClass.cbWndExtra		= 0;
windowClass.hInstance		= hInstance;
windowClass.hIcon			= LoadIcon(NULL, IDI_APPLICATION);	// default icon
windowClass.hCursor			= LoadCursor(NULL, IDC_ARROW);		// default arrow
windowClass.hbrBackground	= NULL;								// don't need background
windowClass.lpszClassName	= "GLClass";
windowClass.hIconSm			= LoadIcon(NULL, IDI_WINLOGO);		// windows logo small icon

if (!RegisterClassEx(&windowClass)){
DWORD err = GetLastError();
return 0;
}

CreateGLWindow(windowClass,windowRect,hInstance,&hwnd);
...

Looking good so far...
bool CreateGLWindow(WNDCLASSEX windowClass, RECT windowRect, HINSTANCE hInstance, HWND *hwnd){

DWORD	   dwExStyle;		// Window Extended Style
DWORD	   dwStyle;			// Window Style

HGLRC hRC;

if (fullscreen)								// fullscreen?
{

int monitors = GetSystemMetrics(SM_CMONITORS);

DISPLAY_DEVICE dd;
DEVMODE dm;
dd.cb= sizeof(dd);

std::vector<DISPLAY_DEVICE> devices;
std::vector<DEVMODE> devmodes;
int i = 0;
while(EnumDisplayDevices(0,i,&dd,0)){
devices.push_back(dd);
EnumDisplaySettings(dd.DeviceName,ENUM_CURRENT_SETTINGS,&dm);
devmodes.push_back(dm);
i++;
}

DEVMODE dmScreenSettings;					// device mode
memset(&dmScreenSettings,0,sizeof(dmScreenSettings));
dmScreenSettings.dmSize = sizeof(dmScreenSettings);
dmScreenSettings.dmPelsWidth = devmodes[1].dmPelsWidth;			// screen width
dmScreenSettings.dmPelsHeight = devmodes[1].dmPelsHeight;			// screen height
dmScreenSettings.dmBitsPerPel = devmodes[1].dmBitsPerPel;				// bits per pixel
dmScreenSettings.dmFields=DM_BITSPERPEL|DM_PELSWIDTH|DM_PELSHEIGHT;

if (ChangeDisplaySettingsEx(devices[1].DeviceName,&dmScreenSettings,0, CDS_FULLSCREEN,0) != DISP_CHANGE_SUCCESSFUL)
{
MessageBox(NULL, "Display mode failed", NULL, MB_OK);
fullscreen = FALSE;
}
}

if (fullscreen)								// Are We Still In Fullscreen Mode?
{
dwExStyle=WS_EX_APPWINDOW;					// Window Extended Style
dwStyle=WS_POPUP;						// Windows Style
ShowCursor(FALSE);						// Hide Mouse Pointer
}
else
{
dwExStyle=WS_EX_APPWINDOW | WS_EX_WINDOWEDGE;			// Window Extended Style
dwStyle=WS_OVERLAPPEDWINDOW;					// Windows Style
}

*hwnd = CreateWindowEx(NULL,									// extended style
"GLClass",							// class name16829936
"Isle",	// app name
dwStyle | WS_CLIPCHILDREN |
WS_CLIPSIBLINGS,
0, 0,								// x,y coordinate
windowRect.right - windowRect.left,
windowRect.bottom - windowRect.top, // width, height
NULL,								// handle to parent
hInstance,							// application instance
NULL);								// no extra params

This section is the only difference I have between fullscreen and windowed mode, just changing some Display Settings. I'm not real experienced here so its possible I'm doing something stupid. Calling CreateWindowEx fires off a CALLBACK MainWindowProc with message WM_SIZE, where I'm checking for opengl error. In windowed mode this passes just fine, while failing with GL_INVALID_OPERATION in fullscreen. Any ideas?

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I don't understand this:
devices[1]...
Anyway, could you post the actual change code? If it's just a ChangeDisplaySettingsEx, then I think you need a AdjustWindowRectEx too.

What happens if you start with fullscreen initially? (not just toggling to it).

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Quote:
 ...devices[1]...

Guess I should have explained that better. I'm using a two-monitor environment, and that is the device for my second monitor. Code could be incorrect, but I'm just cobbling together bits and pieces I've found from various sources. I get the same behavior if I use devices[0] too (main monitor).

Quote:
 Anyway, could you post the actual change code? If it's just a ChangeDisplaySettingsEx, then I think you need a AdjustWindowRectEx too.

I'm not sure I understand what 'actual change code' you're referring to. That is every line of code I use up through when I get the glError. I do have AdjustWindowRectEx too, its the last line before CreateWindowEx.

Quote:
 What happens if you start with fullscreen initially? (not just toggling to it).
I'm not sure how you would do this.

Thanks for looking.

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Sorry, I guess it's morning.

I was referring to your change-to-fullscreen code. When you push the "change-to-fullscreen-key".

Or maybe I misunderstood something.

"This section is the only difference I have between fullscreen and windowed mode, just changing some Display Settings"

I don't understand this sentence. Clarifying "some Display Settings" would be useful.

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Oh sorry. This is the initialization code for my program, I'm not changing it once its running.

Program opens with WinMain, WinMain calls CreateGLWindow, CreateGLWindow calls CreateWindowEx which causes WM_SIZE message where the opengl error is caught.

When I said the only difference between fullscreen and windowed mode, I meant that I'm selecting fullscreen or windowed mode by hardcoding variable 'fullscreen' to true or false. When I start defined to windowed mode initialization works fine, if I start in fullscreen mode the initialization is causing errors.

I said I was 'changing Display Settings' because I was calling the winapi function "ChangeDisplaySettings". Not actually changing anything once its running.

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What happens if you remove the device-lister stuff, and just use hard-coded devmode settings for the fullscreen?

My window create for fullscreen:
CreateWindowEx(WS_EX_TOPMOST,WIND_CLASS_NAME,WIND_CLASS_NAME,WS_POPUP|WS_VISIBLE,...

You doesn't seem to use the dwExstyle (you pass NULL instead)

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Maybe you miss this from the device lister stuff:
memset(&dd,0,sizeof(DISPLAY_DEVICE));
memset(&dm,0,sizeof(DEVMODE));//the same for other DEVMODE variables
dm.dmSize = sizeof(DEVMODE);//the same for other DEVMODE variables
There are some flags that need to be set to zero (or something else). I use zero.

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Found the problem, I was calling setup projection on WM_SIZE event. For some reason when using WS_POPUP style on the first WM_SIZE event the OpenGL context is not ready, although when using the WS_OVERLAPPEDWINDOW style the context is ready on the first WM_SIZE event.

Anyway just threw an if(isInitialized) check around my projection setup and its got no problem now.

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