The tool to dump current displays layout the same way it is done by arandr...

randr_dump.c

#include <stdio.h>
#include <string.h>
#include <stdint.h>
#include <stdbool.h>
#include <assert.h>

#define startsWith(a, b) (strstr(a, b) == a)

int main() {
	char chunk[512];
	struct output {
		char name[64];
		bool connected;
		bool active;
		char mode[32];
		char pos[32];
		char rotate[9];
	} outputs[16] = {0};
	
	FILE * fp = popen("xrandr --verbose", "r");
	if (!fp) {
        perror("popen");
        return -1;
    }
    
    size_t i = 0;
    bool firstmode = true;
	printf("xrandr");
	
	while (fgets(chunk, sizeof(chunk)-1, fp) != NULL) {
		if (startsWith(chunk, "Screen ") || startsWith(chunk, "\t")) //Noise
			continue;
		else if (startsWith(chunk, "  ")) { // Mode, width or height
			if (!strstr(chunk, "current"))
				continue;

			uint16_t width, height;

			strstr(chunk+2, " ")[0] = '\0';
			strcpy(outputs[i].mode, chunk+2);

			fgets(chunk, sizeof(chunk)-1, fp);
			sscanf(chunk, "        %*c: %*s  %hd start", &width);

			fgets(chunk, sizeof(chunk)-1, fp);
			sscanf(chunk, "        %*c: %*s  %hd start", &height);

			printf(" --output %s --mode %s --pos %s --rotate %s", 
				outputs[i].name, outputs[i].mode, outputs[i].pos, outputs[i].rotate);
		} else { // Output
			if (firstmode) firstmode = false; else i++;

			char * pch = strtok(chunk, " ");
			strcpy(outputs[i].name, pch);

			pch = strtok(NULL, " ");
			if (!strcmp(pch, "connected") || 
			   (!strcmp(pch, "unknown") && !strcmp(strtok(NULL, " "), "connection")))
				outputs[i].connected = true;

			pch = strtok(NULL, " ");
			if (!strcmp(pch, "primary"))
				pch = strtok(NULL, " ");

			if (!startsWith(pch, "(")) {
				uint32_t left, top;
				outputs[i].active = true;
				sscanf(pch, "%*ux%*u+%u+%u", &left, &top);
				sprintf(outputs[i].pos, "%hdx%hd", left, top);

				strtok(NULL, " "); // Skip modeid
				strcpy(outputs[i].rotate, strtok(NULL, " "));
			} else 
				printf(" --output %s --off", outputs[i].name);
		}
	}
	printf("\n");
	
	pclose(fp);
	return 0;
}