EGLDisplay对GBM [英] EGLDisplay on GBM

问题描述

我想通过创建一个EGL OpenGL上下文。正如我不会实际绘制，我想结合使用与pbuffer而使GBM的平台。这是code（C99）：

I want to create an OpenGL context through EGL. As I won't actually draw, I want to use Pbuffers in conjunction with the GBM platform. This is the code (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，出现以下错误：

It fails with the following error:

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);

<一个href=\"http://virtuousgeek.org/blog/index.php/jbarnes/2011/10/31/writing_stanalone_programs_with_egl_and_\">This是我把为例页面。

我很惊讶，因为我建梅萨与 - 与东瀛平台= DRM，韦兰，X11 ，而且，即使它说的这里的 EGL_DEFAULT_DISPLAY 映射到指定的第一个平台，它是一个别名 _XDisplay * 我的系统上。

I'm surprised, because I built Mesa with --with-egl-platforms=drm,wayland,x11, and, even though it is stated here that EGL_DEFAULT_DISPLAY maps to the first platform specified, it is an alias for _XDisplay * on my system.

--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.

据我所知，韦斯顿创建在裸KMS借鉴GBM之上的EGLDisplay。我看着它的code，我已经grepped相关的系统头寻找一个解决方案，但它似乎并不存在。

AFAIK, Weston creates an EGLDisplay on top of GBM for drawing on bare KMS. I've looked at its code, and I've grepped the pertinent system headers looking for a solution, but it seems to not be there.

FWIW，我使用梅萨10.0上的Radeon HD 3200，Linux的3.12.6，GCC 4.8.2。

FWIW, I'm using Mesa 10.0 on a Radeon HD 3200, Linux 3.12.6, GCC 4.8.2.

推荐答案

您说

我想结合使用与pbuffer而使GBM的平台。

I want to use Pbuffers in conjunction with the GBM platform.

EGL / GBM不支持pbuffer而使。它不支持像素图无论是。

EGL/GBM does not support Pbuffers. It doesn't support Pixmaps either.

要创建EGL / GBM一个屏幕外表面，你必须通过一个gbm_surface到eglCreateWindowSurface。 窗口是用词不当。没有真正的窗口被创建。得到的缓冲区将保持屏幕外，除非你使用内核的KMS的API将其发布到显示器上。

To create an offscreen surface with EGL/GBM, you must pass a gbm_surface to eglCreateWindowSurface. "Window" is a misnomer. No real "window" gets created. The resultant buffer will remain offscreen unless you use the kernel's KMS APIs to post it to the display.

可是......为什么你的程序编译失败，这不是。当调用eglGetDisplay和eglCreateWindowSurface，必须转换是这样的：

But... that's not why your program fails to compile. When calling eglGetDisplay and eglCreateWindowSurface, you must cast like this:

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

如果您正在使用包含提交<一台面href=\"http://cgit.freedesktop.org/mesa/mesa/commit/src/egl/main?id=468cc866b4b308cee40470f06b31002c6c56da96\"相对=nofollow> 468cc86 ，那么你就可以通过，而不是使用eglGetPlatformDisplayEXT和eglCreatePlatformWindowSurface这样避免了铸造：

If you are using a Mesa that contains commit 468cc86, then you may avoid the casting by instead using eglGetPlatformDisplayEXT and eglCreatePlatformWindowSurface like this:

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

无论您选择使用香草EGL功能或较新的平台功能EGL，你应该参考的例子code中的 EGL_MESA_platform_gbm 规范为指导。

这篇关于EGLDisplay对GBM的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！