OpenGL硬件加速指南

OpenGLRenderer.cpp位于Framewoks/base/libs/hwui中

 

1.构造函数：

 

OpenGLRenderer::OpenGLRenderer(): mCaches(Caches::getInstance()) {
    mShader = NULL;
    mColorFilter = NULL;
    mHasShadow = false;

    memcpy(mMeshVertices, gMeshVertices, sizeof(gMeshVertices));

    mFirstSnapshot = new Snapshot;
}

2.设置View_Projection 和 ViewPort

  

void OpenGLRenderer::setViewport(int width, int height) {
    glDisable(GL_DITHER);
    glViewport(0, 0, width, height);
    mOrthoMatrix.loadOrtho(0, width, height, 0, -1, 1);

    mWidth = width;
    mHeight = height;

    mFirstSnapshot->height = height;
    mFirstSnapshot->viewport.set(0, 0, width, height);

    mDirtyClip = false;
}

 3.Prepare

  

void OpenGLRenderer::prepare(bool opaque) {
    prepareDirty(0.0f, 0.0f, mWidth, mHeight, opaque);
}

void OpenGLRenderer::prepareDirty(float left, float top, float right, float bottom, bool opaque) {
    mCaches.clearGarbage();

    mSnapshot = new Snapshot(mFirstSnapshot,
            SkCanvas::kMatrix_SaveFlag | SkCanvas::kClip_SaveFlag);
    mSnapshot->fbo = getTargetFbo();

    mSaveCount = 1;

    glViewport(0, 0, mWidth, mHeight);

    glEnable(GL_SCISSOR_TEST);
    glScissor(left, mSnapshot->height - bottom, right - left, bottom - top);
    mSnapshot->setClip(left, top, right, bottom);

    if (!opaque) {
        glClearColor(0.0f, 0.0f, 0.0f, 0.0f);
        glClear(GL_COLOR_BUFFER_BIT);
    }
}

 4.Interrupt

 

void OpenGLRenderer::interrupt() {
    if (mCaches.currentProgram) {
        if (mCaches.currentProgram->isInUse()) {
            mCaches.currentProgram->remove();
            mCaches.currentProgram = NULL;
        }
    }
    mCaches.unbindMeshBuffer();
}

 

5.Resume

  void OpenGLRenderer::resume() {
    glViewport(0, 0, mSnapshot->viewport.getWidth(), mSnapshot->viewport.getHeight());

    glEnable(GL_SCISSOR_TEST);
    dirtyClip();

    glDisable(GL_DITHER);

    glBindFramebuffer(GL_FRAMEBUFFER, getTargetFbo());
    glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, 0);

    mCaches.blend = true;
    glEnable(GL_BLEND);
    glBlendFunc(mCaches.lastSrcMode, mCaches.lastDstMode);
    glBlendEquation(GL_FUNC_ADD);
}

 

6. Finish

 

void OpenGLRenderer::finish() {
#if DEBUG_OPENGL
    GLenum status = GL_NO_ERROR;
    while ((status = glGetError()) != GL_NO_ERROR) {
        LOGD("GL error from OpenGLRenderer: 0x%x", status);
        switch (status) {
            case GL_OUT_OF_MEMORY:
                LOGE("  OpenGLRenderer is out of memory!");
                break;
        }
    }
#endif
#if DEBUG_MEMORY_USAGE
    mCaches.dumpMemoryUsage();
#else
    if (mCaches.getDebugLevel() & kDebugMemory) {
        mCaches.dumpMemoryUsage();
    }
#endif
}