Function gmtplot_shift_gridline

src/gmt_plot.c:917–938

}

GMT_LOCAL double gmtplot_shift_gridline (struct GMT_CTRL *GMT, double val, unsigned int type) {
	/* Only for oblique projections: If any of the corners are exactly multiples of annotation
	 * or tick intervals then the gridline intersection may fail (tangent or slightly outside
	 * due to round-off).  We determine which gridlines go through the corners and shift them
	 * a tiny bit to the inside to ensure crossings */
	double shift = 0.0;
	if (!GMT->common.R.oblique) return shift;	/* Return zero if not an oblique projection */

	if (type == GMT_X) {
		if (gmt_M_360_range (val, GMT->common.R.wesn_orig[XLO])) val = GMT->common.R.wesn_orig[XLO];
		else if (gmt_M_360_range (val, GMT->common.R.wesn_orig[XHI])) val = GMT->common.R.wesn_orig[XHI];
		if (doubleAlmostEqualZero (val, GMT->common.R.wesn_orig[XLO])) shift = +GMT_CONV4_LIMIT * fabs (GMT->common.R.wesn_orig[XHI] - GMT->common.R.wesn_orig[XLO]);	/* Add this to lon to get a slightly larger longitude to ensure crossing */
		else if (doubleAlmostEqualZero (val, GMT->common.R.wesn_orig[XHI])) shift = -GMT_CONV4_LIMIT * fabs (GMT->common.R.wesn_orig[XHI] - GMT->common.R.wesn_orig[XLO]);	/* Add this to lon to get a slightly smaller longitude to ensure crossing */
	}
	else {
		if (doubleAlmostEqualZero (val, GMT->common.R.wesn_orig[YLO])) shift = +GMT_CONV4_LIMIT * fabs (GMT->common.R.wesn_orig[YHI] - GMT->common.R.wesn_orig[YLO]);	/* Add this to lon to get a slightly larger longitude to ensure crossing */
		else if (doubleAlmostEqualZero (val, GMT->common.R.wesn_orig[YHI])) shift = -GMT_CONV4_LIMIT * fabs (GMT->common.R.wesn_orig[YHI] - GMT->common.R.wesn_orig[YLO]);	/* Add this to lon to get a slightly smaller longitude to ensure crossing */

	}
	if (shift != 0.0) GMT_Report (GMT->parent, GMT_MSG_INFORMATION, "Adjusted argument %g by %g\n", val, shift);
	return shift;
}

/*	FANCY RECTANGULAR PROJECTION MAP BOUNDARY	*/