# OpenGL EGL fails eglMakeCurrent when using Dear ImGui

**URL:** <https://community.khronos.org/t/opengl-egl-fails-eglmakecurrent-when-using-dear-imgui/109983>\
**Category:** OpenGL: Advanced Coding\
**Created:** [August 9, 2023, 12:18pm UTC](https://community.khronos.org/t/opengl-egl-fails-eglmakecurrent-when-using-dear-imgui/109983 "2023-08-09T12:18:55Z")\
**Posts on this page:** 3\
**Page:** 1

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**Author:** ![spock69](https://community.khronos.org/letter_avatar_proxy/v4/letter/s/8dc957/32.png) [@spock69](https://community.khronos.org/u/spock69)\
**Post date:** [August 9, 2023, 12:18pm UTC](https://community.khronos.org/t/opengl-egl-fails-eglmakecurrent-when-using-dear-imgui/109983/1 "2023-08-09T12:18:55Z")

</div>

Please help,

I have created a program that uses **OpenGL ES** version 3.2 with **OpenGL EGL** defining the context and surface for _headless_ rendering. I am able to render various images to image files without any problem.

However, I am now attempting to use this setup within the context of **Dear ImGui** and calling `eglMakeCurrent` function fails. When I check the error code via `eglGetError()` just after calling 'eglMakeCurrent` the value returned is 12288 (`EGL\_SUCCESS`). So it fails but doesn't have an error via `eglGetError()`.

I have no idea what could be going on, but _suspect_ it might be related to multiple context/threads with **OpenGL EGL** and **Dear ImGui**. It seems odd that there is no problem except when I try to use **Dear ImGui** with **OpenGL EGL**

If anyone has had any experience with this and found a solution, any help/hints would be greatly appreciated.

Below is snippet of the code (apologies for length):

Thank you in advance for any help/hint/link.

```auto
#include <EGL/egl.h>
#include <GLES3/gl32.h>
#include <EGL/eglext.h>
#include <sstream>

EGLint CONFIG_ATTRIBS[] = {
    EGL_SURFACE_TYPE, EGL_PBUFFER_BIT,
    EGL_RED_SIZE, 8,
    EGL_GREEN_SIZE, 8,
    EGL_BLUE_SIZE, 8,
    EGL_ALPHA_SIZE, 8,
    EGL_DEPTH_SIZE, 24,
    EGL_STENCIL_SIZE, 8,
    EGL_RENDERABLE_TYPE, EGL_OPENGL_ES3_BIT_KHR,
    EGL_NONE
};

EGLint CONTEXT_ATTRIBS[] = {
    EGL_CONTEXT_MAJOR_VERSION, 3,
    EGL_CONTEXT_MINOR_VERSION, 2,
    EGL_NONE
};

PFNEGLQUERYDEVICESEXTPROC eglQueryDevicesEXT = 
        reinterpret_cast<PFNEGLQUERYDEVICESEXTPROC>(eglGetProcAddress("eglQueryDevicesEXT"));
    PFNEGLGETPLATFORMDISPLAYEXTPROC eglGetPlatformDisplayEXT = 
        reinterpret_cast<PFNEGLGETPLATFORMDISPLAYEXTPROC>(eglGetProcAddress("eglGetPlatformDisplayEXT"));

if(!eglQueryDevicesEXT || !eglGetPlatformDisplayEXT) {
    throw std::runtime_error("Failed to get function pointers for OpenGL EGL extensions");
}

EGLDeviceEXT devices[MAX_DEVICES];
EGLint num_devices;
eglQueryDevicesEXT(MAX_DEVICES, devices, &num_devices);
if(num_devices < 1) {
    throw std::runtime_error("No OpenGL EGL devices found");
}
...
display = eglGetPlatformDisplayEXT(EGL_PLATFORM_DEVICE_EXT, devices[0], 0);
if(display == EGL_NO_DISPLAY) {
    std::stringstream ss;
    ss << eglGetError();
    throw std::runtime_error(std::string("Failed to get OpenGL EGL display: ") + ss.str());
}
EGLint major;
EGLint minor;
if(eglInitialize(display, &major, &minor) != EGL_TRUE) {
    std::stringstream ss;
    ss << eglGetError();
    throw std::runtime_error(std::string("Failed OpenGL EGL initialize: ") + ss.str());
}
EGLint numConfigs;
if(eglChooseConfig(display, CONFIG_ATTRIBS, &configuration, 1, &numConfigs) == EGL_FALSE) {
    std::stringstream ss;
    ss << eglGetError();
    throw std::runtime_error(std::string("OpenGL EGL failed to choose configuration: ") + ss.str());
}

context = eglCreateContext(display, configuration, EGL_NO_CONTEXT, CONTEXT_ATTRIBS);
if(context == EGL_NO_CONTEXT) {
    std::stringstream ss;
    ss << eglGetError();
    throw std::runtime_error(std::string("EGL failed to create context: ") + ss.str());
}

...
// With width = 50, height = 50
EGLint surfaceAttribs[] = {
    EGL_WIDTH, width,
    EGL_HEIGHT, height,
    EGL_NONE
};
EGLSurface surface = eglCreatePbufferSurface(display, configuration, surfaceAttribs);
if(surface == EGL_NO_SURFACE) {
    std::cerr << "EGL failed to create buffer surface\n";
    std::stringstream ss;
    ss << eglGetError();
    throw std::runtime_error(std::string("EGL failed to create buffer surface: ") + ss.str());
}

// The following is where the failure occurs 
if(eglMakeCurrent(display, surface, surface, context) == EGL_FALSE) {
    std::cerr << "EGL failed to make current display\n";
    std::stringstream ss;
    ss << eglGetError();
    throw std::runtime_error(std::string("EGL failed to make current display: ") + ss.str());
}

```

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<div class="post-metadata">

**Author:** ![saierd](https://community.khronos.org/user_avatar/community.khronos.org/saierd/32/12119_2.png) [@saierd](https://community.khronos.org/u/saierd)\
**Post date:** [January 16, 2025, 11:48am UTC](https://community.khronos.org/t/opengl-egl-fails-eglmakecurrent-when-using-dear-imgui/109983/2 "2025-01-16T11:48:57Z")

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Hi,

I observed the same problem when trying to create a rendering context from a library within a Flutter application. The exact type of context and how it was created don’t seem to matter. As soon as I try to run `eglMakeCurrent` in the same process as the Flutter application it returns `EGL_FALSE`, but without any error code.

This probably also depends on the system. I only observed it on a Linux system using X11 and an Nvidia GPU so far.

Have you found a workaround for this?

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<div class="post-metadata">

**Author:** ![saierd](https://community.khronos.org/user_avatar/community.khronos.org/saierd/32/12119_2.png) [@saierd](https://community.khronos.org/u/saierd)\
**Post date:** [January 20, 2025, 7:51am UTC](https://community.khronos.org/t/opengl-egl-fails-eglmakecurrent-when-using-dear-imgui/109983/3 "2025-01-20T07:51:26Z")

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It looks like this is a bug in Nvidia’s implementation of EGL on X11. I found that it is possible to successfully create and activate a context using GLX in exactly the same situation (in my case through the X11 backend of GLFW). So I use that as a fallback for now when activation of the EGL context failed.