OpenGL ES与EGL的关系(二十一)，android高级面试_libglesv2

//调用eglCreateWindowSurface将Surface s转换为本地窗口，

surface = eglCreateWindowSurface(display, config, s.get(), NULL);

context = eglCreateContext(display, config, NULL, NULL);

eglQuerySurface(display, surface, EGL_WIDTH, &w);

eglQuerySurface(display, surface, EGL_HEIGHT, &h);

//eglMakeCurrent后生成的surface就可以利用opengl画图了

if (eglMakeCurrent(display, surface, surface, context) == EGL_FALSE)

return NO_INIT;

return NO_ERROR;

}

egl创建好环境后，调用gl相关命令去画图，注意eglSwapBuffers(mDisplay, mSurface) 函数是非常重要的一个函数，会去触发queueBuffer和dequeueBuffer，图画就一副一副的画出来了。

bool BootAnimation::android()

{

initTexture(&mAndroid[0], mAssets, “images/android-logo-mask.png”);

initTexture(&mAndroid[1], mAssets, “images/android-logo-shine.png”);

// clear screen

glShadeModel(GL_FLAT);

glDisable(GL_DITHER);

glDisable(GL_SCISSOR_TEST);

glClearC

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olor(0,0,0,1);

glClear(GL_COLOR_BUFFER_BIT);

//调用eglSwapBuffers会去触发queuebuffer，dequeuebuffer，

//queuebuffer将画好的buffer交给surfaceflinger处理，

//dequeuebuffer新创建一个buffer用来画图

eglSwapBuffers(mDisplay, mSurface);

glEnable(GL_TEXTURE_2D);

glTexEnvx(GL_TEXTURE_ENV, GL_TEXTURE_ENV_MODE, GL_REPLACE);

const GLint xc = (mWidth - mAndroid[0].w) / 2;

const GLint yc = (mHeight - mAndroid[0].h) / 2;

const Rect updateRect(xc, yc, xc + mAndroid[0].w, yc + mAndroid[0].h);

glScissor(updateRect.left, mHeight - updateRect.bottom, updateRect.width(),

updateRect.height());

// Blend state

glBlendFunc(GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA);

glTexEnvx(GL_TEXTURE_ENV, GL_TEXTURE_ENV_MODE, GL_REPLACE);

const nsecs_t startTime = systemTime();

do {

nsecs_t now = systemTime();

double time = now - startTime;

float t = 4.0f * float(time / us2ns(16667)) / mAndroid[1].w;

GLint offset = (1 - (t - floorf(t))) * mAndroid[1].w;

GLint x = xc - offset;

glDisable(GL_SCISSOR_TEST);

glClear(GL_COLOR_BUFFER_BIT);

glEnable(GL_SCISSOR_TEST);

glDisable(GL_BLEND);

glBindTexture(GL_TEXTURE_2D, mAndroid[1].name);

glDrawTexiOES(x, yc, 0, mAndroid[1].w, mAndroid[1].h);

g