EGLD上的EGLD显示

Question

我想通过EGL创建一个OpenGL上下文.由于我实际上不会绘制,我想将Pbuffers与GBM平台结合使用.这是代码(C99):

#include <stdlib.h>
#include <assert.h>

#include <fcntl.h>
#include <unistd.h>

#include <EGL/egl.h>
#include <EGL/eglext.h>

#include <gbm.h>


int main( void )
{
    assert( eglBindAPI( EGL_OPENGL_API ) == EGL_TRUE );

    int fd = open("/dev/dri/card0", O_RDWR);
    struct gbm_device * gbm = gbm_create_device( fd );

    EGLDisplay dpy = eglGetDisplay( gbm );
    eglInitialize( dpy , NULL , NULL );

    EGLConfig config;
    EGLint n_of_configs;
    assert( eglGetConfigs( dpy , &config , 1 , &n_of_configs ) == EGL_TRUE );

    EGLSurface srf = eglCreatePbufferSurface( dpy , config , NULL );
    assert( srf != EGL_NO_SURFACE );

    EGLContext ctx = eglCreateContext( dpy , config , EGL_NO_CONTEXT , NULL );
    assert( ctx != EGL_NO_CONTEXT );

    assert( eglMakeCurrent( dpy , srf , srf , ctx ) == EGL_TRUE );

    eglDestroySurface( dpy , srf );
    eglDestroyContext( dpy , ctx );
    eglTerminate( dpy );

    gbm_device_destroy( gbm );
    close( fd );

    return EXIT_SUCCESS;
}

它失败并出现以下错误:

test.c: In function ‘main’:
test.c:20:2: error: passing argument 1 of ‘eglGetDisplay’ from incompatible pointer type [-Werror]
  EGLDisplay dpy = eglGetDisplay( gbm );
  ^
In file included from test.c:7:0:
/usr/include/EGL/egl.h:251:31: note: expected ‘EGLNativeDisplayType’ but argument is of type ‘struct gbm_device *’
 EGLAPI EGLDisplay EGLAPIENTRY eglGetDisplay(EGLNativeDisplayType display_id);

这是我作为例子的页面.

我很惊讶,因为我用Mesa构建了Mesa --with-egl-platforms=drm,wayland,x11,尽管这里说明了EGL_DEFAULT_DISPLAY映射到指定的第一个平台,但它是_XDisplay *我系统的别名.

--with-egl-platforms
List the platforms (window systems) to support. Its argument is a comma seprated string such as --with-egl-platforms=x11,drm. It decides the platforms a driver may support. The first listed platform is also used by the main library to decide the native platform: the platform the EGL native types such as EGLNativeDisplayType or EGLNativeWindowType defined for.

AFAIK,Weston在GBM上创建了一个EGLDisplay,用于绘制裸KMS.我已经查看了它的代码,并且我已经找到了相关的系统头来寻找解决方案,但它似乎并不存在.

FWIW,我在Radeon HD 3200,Linux 3.12.6,GCC 4.8.2上使用Mesa 10.0.

Answer 1

你说

我想将Pbuffers与GBM平台结合使用.

EGL/GBM不支持Pbuffers.它也不支持Pixmaps.

要使用EGL/GBM创建屏幕外表面,必须将gbm_surface传递给eglCreateWindowSurface."窗口"是用词不当.没有真正的"窗口"被创建.除非您使用内核的KMS API将其发布到显示器,否则生成的缓冲区将保持屏幕外.

但是......这不是你的程序无法编译的原因.调用eglGetDisplay和eglCreateWindowSurface时,必须像这样进行转换:

eglGetDisplay((EGLNativeDisplayType)my_gbm_device);
eglCreateWindowSurface(egl_dpy, egl_config,
                       (EGLNativeWindowType)my_gbm_surface, NULL);

如果您使用的是包含提交468cc86的Mesa ,那么您可以通过使用eglGetPlatformDisplayEXT和eglCreatePlatformWindowSurface来避免强制转换,如下所示:

eglGetPlatformDisplayEXT(EGL_PLATFORM_GBM_MESA, my_gbm_device, NULL);
eglCreatePlatformWindowSurfaceEXT(egl_dpy, egl_config, my_gbm_surface, NULL);

无论您选择使用vanilla EGL函数还是更新的平台EGL函数,都应该参考EGL_MESA_platform_gbm规范中的示例代码作为指导.