Function clearFB

util/glreadtest.cpp:314–349

Makes sure the frame buffer has been cleared prior to a write

// Makes sure the frame buffer has been cleared prior to a write
void clearFB(void)
{
	unsigned char *buf = NULL;
	size_t bufSize = drawableWidth * drawableHeight * 3;

	if((buf = (unsigned char *)malloc(bufSize)) == NULL)
		THROW("Could not allocate buffer");
	memset(buf, 0xFF, bufSize);
	glPixelStorei(GL_UNPACK_ALIGNMENT, 1);
	glPixelStorei(GL_PACK_ALIGNMENT, 1);
	#ifdef GL_EXT_framebuffer_object
	if(useFBO)
	{
		glDrawBuffer(GL_COLOR_ATTACHMENT0_EXT);
		glReadBuffer(GL_COLOR_ATTACHMENT0_EXT);
	}
	else
	#endif
	{
		glDrawBuffer(GL_FRONT);
		glReadBuffer(GL_FRONT);
	}
	glClearColor(0., 0., 0., 0.);
	glClear(GL_COLOR_BUFFER_BIT);
	glReadPixels(0, 0, drawableWidth, drawableHeight, GL_RGB, GL_UNSIGNED_BYTE,
		buf);
	check_errors("frame buffer read");
	for(size_t i = 0; i < bufSize; i++)
	{
		if(buf[i] != 0)
		{
			fprintf(stderr, "Buffer was not cleared\n");  break;
		}
	}
	free(buf);
}


// Generic GL write test