Getting EGL_BAD_DISPLAY while firing eglquerystring() from application

According to eglQueryString manual :

EGL_BAD_DISPLAY is generated if display is not an EGL display connection.

Are you sure that the EGL display was initialised correctly ?

What does eglGetError returns after eglGetDisplay ?

According to eglQueryString manual :

EGL_BAD_DISPLAY is generated if display is not an EGL display connection.

Are you sure that the EGL display was initialised correctly ?

What does eglGetError returns after eglGetDisplay ?

Hi myy,

Firstly,Thanks for the response.

Here,is the code snipped from where i am getting error :

const char*     const extensionStr = egl.queryString(EGL_NO_DISPLAY, EGL_EXTENSIONS);

#################################################################

Here is my snapshot of whole code.Actually i am querying extension before getting egl_display.

So if i am getting any platformEXT,then i will get EGL display connection using that.Otherwise ,i am trying to get EGL display using legacy method.

IS IT CORRECT WAY?

##################################################################

Whole ocde snippet:

EGLDisplay getDisplay (NativeDisplay& nativeDisplay)

{

        const Library&  egl                                                             = nativeDisplay.getLibrary();

        const bool              supportsLegacyGetDisplay                = (nativeDisplay.getCapabilities() & NativeDisplay::CAPABILITY_GET_DISPLAY_LEGACY) != 0;

        const bool              supportsPlatformGetDisplay              = (nativeDisplay.getCapabilities() & NativeDisplay::CAPABILITY_GET_DISPLAY_PLATFORM) != 0;

        bool                    usePlatformExt                                  = false;

        EGLDisplay              display                                                 = EGL_NO_DISPLAY;

        TCU_CHECK_INTERNAL(supportsLegacyGetDisplay || supportsPlatformGetDisplay);

        if (supportsPlatformGetDisplay)

        {

              const vector<string> platformExts = getPlatformExtensions(egl);<-------------------------------------------------------------------here i am getting error

              usePlatformExt = de::contains(platformExts.begin(), platformExts.end(), string("EGL_EXT_platform_base")) &&

                                               de::contains(platformExts.begin(), platformExts.end(), string(nativeDisplay.getPlatformExtensionName()));

        }

        if (usePlatformExt)

        {

                tcu::print("##### 2DISPLAY = %d\n",(EGLDisplay)display);

                const vector<EGLint>    legacyAttribs   = toLegacyAttribList(nativeDisplay.getPlatformAttributes());

                display = egl.getPlatformDisplayEXT(nativeDisplay.getPlatformType(), nativeDisplay.getPlatformNative(), &legacyAttribs[0]);

                EGLU_CHECK_MSG(egl, "eglGetPlatformDisplayEXT()");

                TCU_CHECK(display != EGL_NO_DISPLAY);

        }

So, after trying to build a minimal eglQueryString example, I found two problems :

- If eglGetDisplay is not called, eglQueryString will return NULL and an EGL Error will be raised.

- If eglInitialize is not called, eglQueryString will also return NULL and an EGL Error will be raised.

Here's a quick working minimal example on how to use of eglQueryString. The example is in C but should be easy to adapt.

/* Compile with gcc -g3 -o example example.c -lX11 -lEGL */

#include <assert.h>
#include <stdio.h>
#include <EGL/egl.h>
#include <EGL/eglplatform.h>

void printEGLError();

int main(void) {
  Display* x_display = XOpenDisplay(NULL);
  EGLDisplay display = eglGetDisplay(x_display);
  assert(display != EGL_NO_DISPLAY);

  EGLint major, minor;
  eglInitialize(display, &major, &minor);
  char *string = eglQueryString(display, EGL_CLIENT_APIS);
  assert(string);

  printf("%s\n", string);

  return 0;
}

/* Use printEGLError to show a description of the last EGL Error.
  The descriptions are taken from the eglGetError manual */
#define ERROR_DESC(...) fprintf(stderr, "%s\n", __VA_ARGS__); break

void printEGLError() {

  switch(eglGetError()) {

  case(EGL_SUCCESS):
    ERROR_DESC("The last function succeeded without error.");
  case(EGL_NOT_INITIALIZED):
    ERROR_DESC("EGL is not initialized, or could not be initialized, for the specified EGL display connection.");
  case(EGL_BAD_ACCESS):
    ERROR_DESC("EGL cannot access a requested resource (for example a context is bound in another thread).");
  case(EGL_BAD_ALLOC):
    ERROR_DESC("EGL failed to allocate resources for the requested operation.");
  case(EGL_BAD_ATTRIBUTE):
    ERROR_DESC("An unrecognized attribute or attribute value was passed in the attribute list.");
  case(EGL_BAD_CONTEXT):
    ERROR_DESC("An EGLContext argument does not name a valid EGL rendering context.");
  case(EGL_BAD_CONFIG):
    ERROR_DESC("An EGLConfig argument does not name a valid EGL frame buffer configuration.");
  case(EGL_BAD_CURRENT_SURFACE):
    ERROR_DESC("The current surface of the calling thread is a window, pixel buffer or pixmap that is no longer valid.");
  case(EGL_BAD_DISPLAY):
    ERROR_DESC("An EGLDisplay argument does not name a valid EGL display connection.");
  case(EGL_BAD_SURFACE):
    ERROR_DESC("An EGLSurface argument does not name a valid surface (window, pixel buffer or pixmap) configured for GL rendering.");
  case(EGL_BAD_MATCH):
    ERROR_DESC("Arguments are inconsistent (for example, a valid context requires buffers not supplied by a valid surface).");
  case(EGL_BAD_PARAMETER):
    ERROR_DESC("One or more argument values are invalid.");
  case(EGL_BAD_NATIVE_PIXMAP):
    ERROR_DESC("A NativePixmapType argument does not refer to a valid native pixmap.");
  case(EGL_BAD_NATIVE_WINDOW):
    ERROR_DESC("A NativeWindowType argument does not refer to a valid native window.");
  case(EGL_CONTEXT_LOST):
    ERROR_DESC("A power management event has occurred. The application must destroy all contexts and reinitialise OpenGL ES state and objects to continue rendering. ");
  }
}

Hi vaibhav810,

const char* const extensionStr = egl.queryString(EGL_NO_DISPLAY, EGL_EXTENSIONS);

QueryString in this case is expecting a valid EGL_DISPLAY.

Could you try to initialize your display using this method:

display = eglGetDisplay(EGL_DEFAULT_DISPLAY);
if(display == EGL_NO_DISPLAY)
{
     EGLint error = eglGetError();
     LOGE("eglGetError(): %i (0x%.4x)\n", (int)error, (int)error);
     LOGE("No EGL Display available at %s:%i\n", __FILE__, __LINE__);
     exit(1);
}

And then use the display you got inside your query string.

For implementation example, you can refer yourself to the simple-framework project included in our OpenGL ES SDK for linux available here: Mali OpenGL ES SDK for Linux - Mali Developer Center