OpenGl ES实施

1.get显示器句柄

EGLDisplay* egl_display = eglGetDisplay(EGL_DEFAULT_DISPLAY);
// or
EGLNativeDisplayType hDisplayType = static_cast<EGLNativeDisplayType>(fbGetDisplayByIndex(0));
EGLDisplay* egl_display = eglGetDisplay(hDisplayType );

2.初始化EGL

eglInitialize(egl_display, &majorVer, &minorVer);

EGL将在初始化时，返回主要和次要版本

2.1 选择配置

EGLint attributes[] = {EGL_RENDERABLE_TYPE, EGL_OPENGL_ES3_BIT_KHR. EGL_NONE};
EGLConfig config;
EGLint config_count;
bool chosen = eglChooseConfig(display, attributes, config, 1, &config_count);

3.创建窗口

4.获取上下文环境

// 传参获取到的显示器句柄和配置值

EGLint  context_attribs[] =
{
    EGL_CONTEXT_CLIENT_VERSION , 3,
    EGL_NONE
};

EGLContext context = eglCreateContext(egl_display, config, NULL, context_attribs);

5.设置上下文环境

eglMakeCurrent(egl_display, windowSurface, windowSurface, context);

6.bind API

eglBindAPI(EGL_OPENGL_ES_API);

实施code

#include <stdio.h>
#include <EGL/egl.h>
#include <EGL/eglext.h>
#include <EGL/eglplatform.h>
#include <EGL/eglvivante.h>

#include <GLES2/gl2.h>
#include <GLES2/gl2ext.h>
#include <GLES3/gl31.h>

int main(int argc, char **argv)
{
    // 1.get display
      EGLNativeDisplayType hDisplayType = static_cast<EGLNativeDisplayType>(fbGetDisplayByIndex(0));
    EGLDisplay  display = eglGetDisplay(hDisplayType);
    if (EGL_SUCCESS != eglGetError()) {
        printf("get display error
");
    }

    // 2.init
    EGLint major, minor;
    eglInitialize(display, &major, &minor);

    // 3.choose config
    EGLint attribs[] = 
    {
        EGL_RENDERABLE_TYPE, EGL_OPENGL_ES3_BIT_KHR,
        EGL_NONE
    };
    EGLConfig configs[100];
    EGLint config_size = 0;
    EGLint num_config;
    bool res_chose = eglChooseConfig(display, attribs, configs, config_size, &num_config);
    if (EGL_SUCCESS != eglGetError()) {
        printf("choose config error
");
    }
    if (res_chose) {
        printf("3.choose OK num_config[%d]
", num_config);
    }
    else {
        printf("3.choose failed
");
    }

    // 4.create context
    printf("4.create context begin
");
    EGLContext context;
    int num = 0;
    EGLint  context_attribs[] =
    {
        EGL_CONTEXT_CLIENT_VERSION , 3,
        EGL_NONE
    };
    for (int i = 0; i < num_config; i++) {
        context = eglCreateContext(display, configs[i], EGL_NO_CONTEXT, context_attribs);
        if (EGL_SUCCESS != eglGetError()) {
            printf("create context error
");
        }
        else {
            printf("i[%d]
", i);
            num = i;
            break;
        }
    }
    printf("4.create context end
");

    // create surface
    EGLint surfAttribs[] =
    {
        EGL_COLORSPACE, EGL_COLORSPACE_sRGB,
        EGL_NONE
    };
    int m_width = 1;
    int m_height = 1;
    EGLNativeWindowType win = (EGLNativeWindowType)fbCreateWindow(hDisplayType, 0, 0, m_width, m_height);
    EGLSurface surface =  eglCreateWindowSurface(display, configs[num], win, surfAttribs);
    if (EGL_SUCCESS != eglGetError()) {
        printf("create surface error
");
    }

    // 5.make current
    printf("5.make current begin
");
    eglMakeCurrent(display, EGL_NO_SURFACE, EGL_NO_SURFACE, context);
    // eglMakeCurrent(display, surface, surface, context);
    if (EGL_SUCCESS != eglGetError()) {
        printf("make current error
");
    }
    if (EGL_NO_CONTEXT != context && eglGetCurrentContext() == context) {
        printf("5.make current OK
");
    }
    else {
        printf("5.make current failed
");
    }

    // 6.bind API
    printf("6.bind opengl es API begin
");
    bool res_bind = eglBindAPI(EGL_OPENGL_ES_API);
    if (EGL_SUCCESS != eglGetError()) {
        printf("bind API error
");
    }
    if (res_bind) {
        printf("6.bind OK
");
    }
    else {
        printf("6.bind failed
");
    }

    // 7.test gl api
    printf("7.test egl version[%s]
", eglQueryString(display, EGL_VERSION));
    printf("7.test version_name[%s]
", glGetString(GL_VERSION));
    GLint major_version = 0;
    GLint minor_version = 0;
    glGetIntegerv(GL_MAJOR_VERSION, &major_version);
    glGetIntegerv(GL_MINOR_VERSION, &minor_version);
    printf("7.test glGetIntegerv major[%d] minor[%d]
", major_version, minor_version);
    if (glGetError() == GL_NO_ERROR) {
        printf("7.test gl error api OK
");
    }
    else {
        printf("7.test gl error api failed
");
    }

}

断开连接和释放

eglMakeCurrent(display, EGL_NO_SURFACE , EGL_NO_SURFACE , EGL_NO_CONTEXT);
eglDestroySurface(display, surface);
eglDestroyContext(display, context);
eglTerminate(display);