# Full-screen problem with multiple displays (Microsoft Windows + OpenGL), with solution, sort of

**URL:** <https://discourse.glfw.org/t/full-screen-problem-with-multiple-displays-microsoft-windows-opengl-with-solution-sort-of/1799>\
**Category:** support\
**Created:** [March 21, 2021, 8:37am UTC](https://discourse.glfw.org/t/full-screen-problem-with-multiple-displays-microsoft-windows-opengl-with-solution-sort-of/1799 "2021-03-21T08:37:59Z")\
**Posts on this page:** 11\
**Page:** 1

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**Author:** ![epajarre](https://yyz1.discourse-cdn.com/flex035/user_avatar/discourse.glfw.org/epajarre/32/479_2.png) [@epajarre](https://discourse.glfw.org/u/epajarre)\
**Post date:** [March 21, 2021, 8:37am UTC](https://discourse.glfw.org/t/full-screen-problem-with-multiple-displays-microsoft-windows-opengl-with-solution-sort-of/1799/1 "2021-03-21T08:37:59Z")

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I met an odd problem with creating multiple full screen windows (on multiple displays).  
This works for me OK with single Nvidia card and multiple displays, it has also worked with two older Nvidia cards with old drivers (and old Windows?). But now it failed with two current generation Nvidia cards (3070) and latest Windows + Driver version. Tested with GLFW 3.3.2 and shortly with 3.3.3.

The error code I am receiving is:  
GLFW(65543)(WGL: Failed to create OpenGL context)

The failure happens when creating the second full screen window. The two screens in question are connected to the same card. Some tests which placed the windows on screens from different graphics cards actually seemed to work. I did experiment with adding delay between creating windows, but that didn’t seem to help.

I am currently not able to really debug this issue, because I have only seen it on customer site, where I have been testing using remote access.

After searching other full-screen related threads on this site, I seem to have found some kind of solution for this problem. The program works if I first create normal windows on the target displays and then later change them to full screen mode.

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**Author:** ![dougbinks](https://yyz1.discourse-cdn.com/flex035/user_avatar/discourse.glfw.org/dougbinks/32/39_2.png) [@dougbinks](https://discourse.glfw.org/u/dougbinks)\
**Post date:** [March 21, 2021, 2:49pm UTC](https://discourse.glfw.org/t/full-screen-problem-with-multiple-displays-microsoft-windows-opengl-with-solution-sort-of/1799/2 "2021-03-21T14:49:01Z")

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Testing GLFW 3.3.3 would be useful, as there are some monitor related fixes for Win32.

If this still fails it would be handy to add some logging output at various stages in GLFW to track down the problem, and I can help with that.

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**Author:** ![epajarre](https://yyz1.discourse-cdn.com/flex035/user_avatar/discourse.glfw.org/epajarre/32/479_2.png) [@epajarre](https://discourse.glfw.org/u/epajarre)\
**Post date:** [March 21, 2021, 5:41pm UTC](https://discourse.glfw.org/t/full-screen-problem-with-multiple-displays-microsoft-windows-opengl-with-solution-sort-of/1799/3 "2021-03-21T17:41:43Z")

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Seems to fail the same way, when I retested with 3.3.3.

It manages to create the first window, but the second window creation fails

My fullscreen window code is as follows: (hope I get it through correctly)

```
GLFWwindow *glfw_fullscreen_win(const char *title,int posx,int posy,
      int sx,int sy,GLFWwindow *share)
{
  GLFWmonitor *monitor=get_monitor(posx,posy,sx,sy);
  if (!monitor){
    fprintf(stderr,"glfw_fullscreen_win failure\n");
  }else{
    const GLFWvidmode *mode=glfwGetVideoMode(monitor);
    glfwWindowHint(GLFW_RED_BITS,mode->redBits);
    glfwWindowHint(GLFW_GREEN_BITS,mode->greenBits);
    glfwWindowHint(GLFW_BLUE_BITS,mode->blueBits);
    glfwWindowHint(GLFW_REFRESH_RATE,mode->refreshRate);
    sx=mode->width;
    sy=mode->height;
  }
  GLFWwindow *win=glfwCreateWindow(sx,sy,
			   title,monitor,share);
  int rsx,rsy;
  glfwGetWindowSize(win,&rsx,&rsy);
  fprintf(stderr,"Window size is %d %d\n",rsx,rsy);
  return win;

```

}

The get\_monitor and glfwGetVideoMode calls return correct results (and similar results for first and the second window). The glfwCreateWindow call triggers the error callback which produces the  
GLFW(65543)(WGL: Failed to create OpenGL context)

message. It also returns a null pointer which crashes my program in the glfwGetWindowSize step.

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**Author:** ![dougbinks](https://yyz1.discourse-cdn.com/flex035/user_avatar/discourse.glfw.org/dougbinks/32/39_2.png) [@dougbinks](https://discourse.glfw.org/u/dougbinks)\
**Post date:** [March 22, 2021, 11:56am UTC](https://discourse.glfw.org/t/full-screen-problem-with-multiple-displays-microsoft-windows-opengl-with-solution-sort-of/1799/4 "2021-03-22T11:56:07Z")

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Note that `glfwCreateWindow` will return `NULL` on error, so it’s often good to have a backup path:  
[https://www.glfw.org/docs/3.3/group\_\_window.html#ga5c336fddf2cbb5b92f65f10fb6043344](https://www.glfw.org/docs/3.3/group__window.html#ga5c336fddf2cbb5b92f65f10fb6043344)

Do you know what happens if you do not pass `share`? Normally this would produce another error `ERROR_INCOMPATIBLE_DEVICE_CONTEXTS_ARB` rather than `GLFW_VERSION_UNAVAILABLE` which is what you’re seeing, but it’s worth a try.

Note that ‘share’ should not be current on another thread when calling `glfwCreateWindow`.

There are two places which generate this error, one where the context is created by `wglCreateContextAttribsARB` (the route modern OpenGL drivers & hardware shouild take) and one using `wglCreateContext`. If you are building from source it might be worth while to change either message (wgl\_context.c line 733 or 751) to a different message to see which is failing.

If these don’t work, I can look into adding debug output to a branch for you - I take it `fprintf` to `stderr` would work in your build?

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**Author:** ![epajarre](https://yyz1.discourse-cdn.com/flex035/user_avatar/discourse.glfw.org/epajarre/32/479_2.png) [@epajarre](https://discourse.glfw.org/u/epajarre)\
**Post date:** [March 23, 2021, 3:38pm UTC](https://discourse.glfw.org/t/full-screen-problem-with-multiple-displays-microsoft-windows-opengl-with-solution-sort-of/1799/5 "2021-03-23T15:38:13Z")

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(I hope I got my email alerts set up correctly this time, so I can reply sooner)

The fact that my program crashes if the window is not created is not an issue for me, I need that second window, so crashing is a nice “visible” choice.

Share seems to be essential for the problem, if I don’t pass the window to be shared, the second window is created. I cannot be sure if everything is OK, as sharing is needed by my program, but it certainly gets to go much further.

The window creation problem is detected at the 733 line branch.

I added some code to checkout the attributes passed to the wglCreateContextAttribsARB, and it seems like an empty attribute list still exhibits the problem. My original code used the GLFW\_CONTEXT\_RELEASE\_BEHAVIOUR hint, but it doesn’t really seem to matter.

I will try some additional tests later. Thank you for your help, but don’t worry too much for this issue for me, as I can currently work around it by creating the window first in non full screen mode.

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**Author:** ![dougbinks](https://yyz1.discourse-cdn.com/flex035/user_avatar/discourse.glfw.org/dougbinks/32/39_2.png) [@dougbinks](https://discourse.glfw.org/u/dougbinks)\
**Post date:** [March 23, 2021, 4:05pm UTC](https://discourse.glfw.org/t/full-screen-problem-with-multiple-displays-microsoft-windows-opengl-with-solution-sort-of/1799/6 "2021-03-23T16:05:20Z")

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> [@epajarre](#):
>
> Share seems to be essential for the problem, if I don’t pass the window to be shared, the second window is created.

This makes me think there is a driver related problem, as both windows use the same graphics card/driver and so should be able to share lists even if on different windows.

> [@epajarre](#):
>
> The window creation problem is detected at the 733 line branch.

This is the modern `wglCreateContextAttribsARB` route as expected.

> [@epajarre](#):
>
> The fact that my program crashes if the window is not created is not an issue for me

One solution would be to create the window fullscreen, if that fails fall back to creating it windowed and then go fullscreen. This way you get better behaviour if it works.

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<div class="post-metadata">

**Author:** ![epajarre](https://yyz1.discourse-cdn.com/flex035/user_avatar/discourse.glfw.org/epajarre/32/479_2.png) [@epajarre](https://discourse.glfw.org/u/epajarre)\
**Post date:** [March 23, 2021, 6:18pm UTC](https://discourse.glfw.org/t/full-screen-problem-with-multiple-displays-microsoft-windows-opengl-with-solution-sort-of/1799/7 "2021-03-23T18:18:07Z")

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Retested some things, mostly for fun.

Similar graphics card, and same driver version, but only one card in computer. OK

On the computer with two cards, if the windows are going to displays which are connected to same card: FAIL

On the computer with two cards, if the windows are going to displays which are connected to different cards: OK

The one card and two card computers have different display types, so the card count is not the only difference, but otherwise they are similar.

I also forced the glfw to use the second context creation path. In that case it is the wglShareLists function which fails. The raw error code is: c00720d0 which I really don’t understand

I might try the alternative window creation sequence you suggested, but so far the “normal window” - → change to → “full screen” has been OK also.

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<div class="post-metadata">

**Author:** ![epajarre](https://yyz1.discourse-cdn.com/flex035/user_avatar/discourse.glfw.org/epajarre/32/479_2.png) [@epajarre](https://discourse.glfw.org/u/epajarre)\
**Post date:** [March 26, 2021, 8:57am UTC](https://discourse.glfw.org/t/full-screen-problem-with-multiple-displays-microsoft-windows-opengl-with-solution-sort-of/1799/8 "2021-03-26T08:57:59Z")

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I think I gave wrong information in my last message. It actually seems that the failing configuration is when the windows are going to monitors attached to **different** graphics cards.

This is of course the more logical case. I will confirm when I get the cables swapped.

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**Author:** ![dougbinks](https://yyz1.discourse-cdn.com/flex035/user_avatar/discourse.glfw.org/dougbinks/32/39_2.png) [@dougbinks](https://discourse.glfw.org/u/dougbinks)\
**Post date:** [March 26, 2021, 9:28am UTC](https://discourse.glfw.org/t/full-screen-problem-with-multiple-displays-microsoft-windows-opengl-with-solution-sort-of/1799/9 "2021-03-26T09:28:31Z")

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This makes a lot more sense if it is the case, as context sharing between contexts created on two different GPUs is unlikely to work.

You can use:

```auto
glGetString( GL_VENDOR );
glGetString( GL_RENDERER );
glGetString( GL_VERSION );
glGetString( GL_SHADING_LANGUAGE_VERSION );

```

to get more information on the context created with the window to see if they are different.

Note that Windows plays some magic with OpenGL, so I suspect your working solution is because the windows are created with the context of one GPU, and when you go fullscreen the window on the second monitor doesn’t go ‘dedicated fullscreen’ but instead is simply a borderless fullscreen window - in OpenGL there is no real distinction but drivers and Windows DWM handle these in the background.

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**Author:** ![Alex\_Ross](https://avatars.discourse-cdn.com/v4/letter/a/a9adbd/32.png) [@Alex\_Ross](https://discourse.glfw.org/u/Alex_Ross)\
**Post date:** [July 2, 2021, 6:48pm UTC](https://discourse.glfw.org/t/full-screen-problem-with-multiple-displays-microsoft-windows-opengl-with-solution-sort-of/1799/10 "2021-07-02T18:48:24Z")

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Ok so I am not a very techy person and have no idea what you guys are saying. Can somebody please explain it to me in simple language? This is an issue I’m having on my Windows 7 computer trying to update my Minecraft.

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**Author:** ![dougbinks](https://yyz1.discourse-cdn.com/flex035/user_avatar/discourse.glfw.org/dougbinks/32/39_2.png) [@dougbinks](https://discourse.glfw.org/u/dougbinks)\
**Post date:** [July 3, 2021, 10:50am UTC](https://discourse.glfw.org/t/full-screen-problem-with-multiple-displays-microsoft-windows-opengl-with-solution-sort-of/1799/11 "2021-07-03T10:50:58Z")

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Hi @Alex_Ross,

Welcome to the GLFW forums.

If you are having issues with an application such as Minecraft you should contact the developers - this forum is for programmers to get support in using GLFW.

If you are having problems in using GLFW as a programmer, could you post what your problem is - and if it is unrelated to trying to create multiple windows on two different GPUs please open another thread.

Cheers,

Doug.