#include	"defs.h"

/*
 * Produce a standard drawing grid.
 *
 * d = distance (tenths of an inch) between major rulings
 */
squares(head,d)
	DL head;
{
	REG INT xx, yy, doti;

	if(d==0){
		rule(head);
	}
	else{
		clearview(head);
		mode(PPLOT);
		for(yy = 0; yy <= 90; yy += 1){
			doti=10;
			if((yy%2)==0) doti=5;
			if((yy%5)==0) doti=2;
			if((yy%10)==0) doti=1;
			for(xx = 0; xx <= 120; xx += doti)
				wvec(point((xx<<7)+512, yy<<7));
		}
	}
}

/*
 * Draw a cross-hatch with a specified distance between lines
 * and an intersection at a given point.
 *
 * p1 and p2 are positions of two intersections
 * h is header item for redrawing picture if necessary.
 */
LOC rule(h)
	DL	h;
{
	DL1	p1, p2;
	REG INT	xx, yy, dd;

	must(cursor(p1));
	wchar(p1, '+');
	must(cursor(p2));
	mode(PPLOT);
	dd = abs(p1->y - p2->y);
	if(dd)
		for(yy = p1->y % dd; yy <= 11520; yy += dd)
			for(xx = 512; xx <= 15872; xx += 128)
				wvec(point(xx, yy));
	dd = abs(p1->x - p2->x);
	if (dd && dd != 128)
		for(xx = (p1->x - 512) % dd + 512; xx <= 15872; xx += dd)
			for(yy = 0; yy <= 11520; yy += 128)
				wvec(point(xx, yy));
}

/*
 * redraw the picture if covered with freckles
 *
 * head is head addr for current mode
 */
LOC clearview(head)
	DL head;
{
	if (!spotless)
		redraw(head);
	spotless = 0;
}