Function gmt_plot_line

src/gmt_plot.c:6169–6316

}

void gmt_plot_line (struct GMT_CTRL *GMT, double *x, double *y, unsigned int *pen, uint64_t n, unsigned int mode) {
	/* Mode = PSL_LINEAR [0] or PSL_BEZIER [1] */
	/* Drawing lines of finite thickness that cross map boundaries is tricky because the exit or entry point
	 * refers to the center line of a finite thickness line but the wider part of the line do not share those
	 * coordinates.  To avoid ugly line gaps we must extend such lines a bit beyond the border and clip so that
	 * things look pretty.  For now we only do this for a few situations:
	 * 1) The map border must be rectangular
	 * 2) The line must be a linear spline and not the Bezier spline
	 * Hopefully we can work to avoid the first case soon */

	uint64_t i, j, im1, ip1, k;
	int way;
	bool close, stop;
	double x_cross[2], y_cross[2];
	double x_ext, y_ext;	/* Coordinates of the external helper point */
	unsigned int start_pen = PSL_MOVE, end_pen = PSL_STROKE;	/* Default pen code of given line endings */
	struct PSL_CTRL *PSL= GMT->PSL;

	if (n < 2) return;

	gmtplot_NaN_pen_up (x, y, pen, n);	/* Ensure we don't have NaNs in the coordinates */

	/* First skip any repeating PSL_MOVE in the beginning since only the last one will matter */
	i = 0;
	while (i < (n-1) && (pen[i+1] & PSL_MOVE)) i++;	/* Skip repeating pen & PSL_MOVE in beginning */
	if ((n-i) < 2) return;	/* Less than 2 points is not a line */
	j = i;	/* j is now the first valid point with a PSL_MOVE */
	/* Then we want to prevent duplicate points since the first point may have a different pen (e.g., include PSL_CLIP) */
	while (i < (n-1) && gmtplot_these_are_duplicates (x[j], y[j], x[i+1], y[i+1])) i++;	/* Skip duplicate points in beginning */
	if ((n-i) < 2) return;	/* Less than 2 points is not a line */
	if (i > j) pen[i] = pen[j];	/* Skipped initial duplicates but must maintain the initial pen code */
	/* Likewise, skip any repeating PSL_MOVE at the end */
	while (n > 1 && (pen[n-1] & PSL_MOVE)) n--;	/* Cut off repeating pen & PSL_MOVE at end */
	if ((n-i) < 2) return;	/* Less than 2 points is not a line */
	/* Then we want to prevent duplicate points at end since the last valid point may have a different pen (e.g., include PSL_CLIP) */
	j = n - 1;	/* j is now last point after initial skip test */
	while (n > 1 && gmtplot_these_are_duplicates (x[j], y[j], x[n-2], y[n-2])) n--;	/* Skip duplicate points at end */
	if ((n-i) < 2) return;	/* Less than 2 points is not a line */
	if (n <= j) {	/* Got a duplicate at the end */
		if ((pen[n-1] & PSL_CLIP) == 0) pen[n-1] = pen[j];	/* Skipped trailing duplicates but must maintain initial pen code of last valid point unless has clip information */
		while (n > 1 && (pen[n-1] & PSL_MOVE)) n--;	/* Cut off repeating pen & PSL_MOVE at end that might result after removing that duplicate */
	}
	for (j = i + 1; j < n && !(pen[j] & PSL_MOVE); j++);	/* j == n means no PSL_MOVEs present */
	close = (j == n) ? (hypot (x[n-1] - x[i], y[n-1] - y[i]) < GMT_CONV4_LIMIT) : false;

	/* First see if we can use the PSL_plotline call directly to save points */

	for (j = i + 1, stop = false; !stop && j < n; j++) stop = (pen[j] & PSL_MOVE || (*GMT->current.map.jump) (GMT, x[j-1], y[j-1], x[j], y[j]));
	if (!stop) {	/* Safe to draw single line directly since no jumping around */
		if (mode == PSL_BEZIER)
			PSL_plotcurve (PSL, &x[i], &y[i], (int)(n - i), PSL_MOVE + PSL_STROKE + close * PSL_CLOSE);
		else {	/* Pay more attention here since exiting lines of finite thickness may need some corrections */
			//bool rect = gmt_M_is_rect_graticule (GMT) || GMT->common.R.oblique;	/* We have a rectangular map boundary */
			bool rect = !(gmt_M_is_azimuthal (GMT) && !GMT->current.proj.polar);
			for (j = i + 1, stop = false; !stop && j < n; j++) stop = (pen[j] & PSL_CLIP);	/* Look for clipped end points */
			if (!rect || !stop)	/* No troubled clip points or it is not a rectangular border */
			//if (!stop)	/* No troubled clip points or it is not a rectangular border */
				PSL_plotline (PSL, &x[i], &y[i], (int)(n - i), PSL_MOVE + PSL_STROKE + close * PSL_CLOSE);