// g++ screena.cpp -o screena -lX11 -lXext -Ofast -mfpmath=both -march=native -m64 -funroll-loops -mavx2 `pkg-config opencv --cflags --libs` && ./screena

  // This includes most headers!

#include "screen.h"

// https://stackoverflow.com/a/39781697/4399859

ScreenShot::ScreenShot() {

	display = XOpenDisplay(nullptr);
	root = DefaultRootWindow(display);

	int count_screens = ScreenCount(display);
	if(count_screens == 0) {
		puts("no screen info!");
	}
	for (int i = 0; i < count_screens; ++i) {
		Screen* screen = ScreenOfDisplay(display, i);
		printf("\tScreen %d: %dX%d\n", i + 1, screen->width, screen->height);
	}

	XGetWindowAttributes(display, root, &window_attributes);
	Screen* screen = window_attributes.screen;
	width = screen->width;
	height = screen->height;
	x = 0;
	y = 0;

	ximg = XShmCreateImage(display, DefaultVisualOfScreen(screen), DefaultDepthOfScreen(screen), ZPixmap, NULL, &shminfo, width, height);

	shminfo.shmid = shmget(IPC_PRIVATE, ximg->bytes_per_line * ximg->height, IPC_CREAT|0777);
	shminfo.shmaddr = ximg->data = (char*)shmat(shminfo.shmid, 0, 0);
	shminfo.readOnly = false;
	if(shminfo.shmid < 0)
		puts("Fatal shminfo error!");
	Status s1 = XShmAttach(display, &shminfo);
	printf("XShmAttach() %s\n", s1 ? "success!" : "failure!");

	init = true;
}

void ScreenShot::operator() (cv::Mat& cv_img){
	if(init)
		init = false;

	XShmGetImage(display, root, ximg, 0, 0, 0x00ffffff);
	cv_img = cv::Mat(height, width, CV_8UC4, ximg->data);
}

ScreenShot::~ScreenShot(){
	if(!init)
		XDestroyImage(ximg);

	XShmDetach(display, &shminfo);
	shmdt(shminfo.shmaddr);
	XCloseDisplay(display);
}