Merge "HWUI: reset buffer state after MakeCurrent"

}

MakeCurrentResult SkiaOpenGLPipeline::makeCurrent() {

    bool wasSurfaceless = mEglManager.isCurrent(EGL_NO_SURFACE);

    // In case the surface was destroyed (e.g. a previous trimMemory call) we

    // need to recreate it here.

    if (!isSurfaceReady() && mNativeWindow) {

    if (!mEglManager.makeCurrent(mEglSurface, &error)) {

        return MakeCurrentResult::AlreadyCurrent;

    }

    // Make sure read/draw buffer state of default framebuffer is GL_BACK. Vendor implementations

    // disagree on the draw/read buffer state if the default framebuffer transitions from a surface

    // to EGL_NO_SURFACE and vice-versa. There was a related discussion within Khronos on this topic.

    // See https://cvs.khronos.org/bugzilla/show_bug.cgi?id=13534.

    // The discussion was not resolved with a clear consensus

    if (error == 0 && wasSurfaceless && mEglSurface != EGL_NO_SURFACE) {

        GLint curReadFB = 0;

        GLint curDrawFB = 0;

        glGetIntegerv(GL_READ_FRAMEBUFFER_BINDING, &curReadFB);

        glGetIntegerv(GL_DRAW_FRAMEBUFFER_BINDING, &curDrawFB);

        GLint buffer = GL_NONE;

        glBindFramebuffer(GL_FRAMEBUFFER, 0);

        glGetIntegerv(GL_DRAW_BUFFER0, &buffer);

        if (buffer == GL_NONE) {

            const GLenum drawBuffer = GL_BACK;

            glDrawBuffers(1, &drawBuffer);

        }

        glGetIntegerv(GL_READ_BUFFER, &buffer);

        if (buffer == GL_NONE) {

            glReadBuffer(GL_BACK);

        }

        glBindFramebuffer(GL_READ_FRAMEBUFFER, curReadFB);

        glBindFramebuffer(GL_DRAW_FRAMEBUFFER, curDrawFB);

        GL_CHECKPOINT(LOW);

    }

    return error ? MakeCurrentResult::Failed : MakeCurrentResult::Succeeded;

}