Function gmtplot_map_gridticks

src/gmt_plot.c:2161–2321

}

GMT_LOCAL void gmtplot_map_gridticks (struct GMT_CTRL *GMT, struct PSL_CTRL *PSL, double w, double e, double s, double n) {
	/* Draw symmetric or asymmetric grid ticks along the courser gridlines for parallels and meridians */
	bool single, point_point = false;
	unsigned int i, j, k, nx, ny, G_nx, G_ny, G_i, G_j, B = 0, E = 0, item[2] = {GMT_GRID_UPPER, GMT_GRID_LOWER};
	double x0, y0, xa, xb, ya, yb, xi, yj, *x = NULL, *y = NULL, *G_x = NULL, *G_y = NULL;
	double angle, Ca, Sa, L, sgn[2] = {1.0, 0.0}, G_dx, G_dy, dx, dy, ys, yn;

	for (k = i = 0; k < 2; k++)
		if (GMT->current.setting.map_grid_cross_type[k] > GMT_CROSS_NORMAL) i++;

	if (i == 0) return;	/* No gridline ticks requested */

	if (gmtplot_get_current_gridlines (GMT, &G_dx, &G_dy)) {
		GMT_Report (GMT->parent, GMT_MSG_ERROR, "Gridline tick embellishments specified but no gridlines have been laid down first\n");
		return;
	}

	if (gmt_M_pole_is_point (GMT)) {	/* Might have two separate domains of gridlines */
		point_point = true;
		if (GMT->current.proj.projection_GMT == GMT_POLAR) {	/* Different for polar graphs since "lat" = 0 is at the center */
			ys =  90.0 - GMT->current.setting.map_polar_cap[0];
			yn = n;
		}
		else {
			ys = MAX (s, -GMT->current.setting.map_polar_cap[0]);
			yn = MIN (n,  GMT->current.setting.map_polar_cap[0]);
		}
	}
	else {	/* No polar cap to worry about */
		ys = s;
		yn = n;
	}
	/* Get the course gridline spacings */
	G_nx = gmtlib_linear_array (GMT, w, e, G_dx, 0.0, &G_x);
	G_ny = gmtlib_linear_array (GMT, ys, yn, G_dy, 0.0, &G_y);

	gmt_map_clip_on (GMT, GMT->session.no_rgb, 3);

	for (k = 0; k < 2; k++) {
		if (gmt_M_is_zero (GMT->current.setting.map_grid_cross_size[k])) continue;

		PSL_comment (PSL, "%s\n", k ? "Map gridticks (secondary)" : "Map gridticks (primary)");

		gmt_setpen (GMT, &GMT->current.setting.map_grid_pen[k]);

		/* Get the detailed gridline tick spacings */
		nx = gmtlib_coordinate_array (GMT, w, e, &GMT->current.map.frame.axis[GMT_X].item[item[k]], &x, NULL);
		ny = gmtlib_coordinate_array (GMT, ys, yn, &GMT->current.map.frame.axis[GMT_Y].item[item[k]], &y, NULL);
		/* Get a small increment in x and y for computing local angle */
		dy = (ny > 1) ? y[1] - y[0] : GMT->current.map.dlat;
		dx = (nx > 1) ? x[1] - x[0] : GMT->current.map.dlon;

		L = 0.5 * fabs (GMT->current.setting.map_grid_cross_size[k]);

		for (G_j = 0; G_j < G_ny; G_j++) {	/* For each gridline parallel */
			yj = G_y[G_j];	/* Current parallel */
			single = (gmt_M_pole_is_point(GMT) && doubleAlmostEqualZero (fabs (yj), 90.0));	/* Only place one grid tick at the poles for maps where the poles are points */
			if (gmt_M_pole_is_point(GMT) && doubleAlmostEqualZero (fabs (yj), 90.0)) continue;	/* No grid tick at single pole points */