When testing that central meridian < |180| take of the [-180 180] vs …

…[0 360] ambiguity. (#8404)

Fix #8403

src/gmt_map.c

@@ -384,9 +384,17 @@ GMT_LOCAL int gmtmap_cyl_validate_clon (struct GMT_CTRL *GMT, unsigned int mode)
  }
  }
  else if (!GMT->common.R.oblique) { /* For regional (<360) areas we cannot have clon > 180 away from either boundary */
- double de, dw;
- dw = fabs (GMT->current.proj.pars[0] - GMT->common.R.wesn[XLO]); if (dw >= 360) dw -= 360.0;
- de = fabs (GMT->current.proj.pars[0] - GMT->common.R.wesn[XHI]); if (de >= 360) de -= 360.0;
+ double de, dw, clon;
+ bool is_clon0360 = GMT->current.proj.pars[0] > 180; /* Is the central meridian in the [0 360] range */;
+ bool is_reg0360 = GMT->common.R.wesn[XLO] > 180 || GMT->common.R.wesn[XHI] > 180; /* Is the region in the [0 360] range */
+
+ clon = GMT->current.proj.pars[0];
+ if (is_clon0360 && !is_reg0360) /* Must take care of not checking for clon < 180 from either boundary and mix -Rg & -Rd */
+ clon -= 360.0;
+ else if (!is_clon0360 && is_reg0360)
+ clon += 360.0;
+ dw = fabs (clon - GMT->common.R.wesn[XLO]); if (dw >= 360) dw -= 360.0;
+ de = fabs (clon - GMT->common.R.wesn[XHI]); if (de >= 360) de -= 360.0;
  if (dw > 180.0 || de > 180.0) {
  if (mode == 2) { /* Yield an error if fixed central longitude, range < 360, and exceed 180 to the border from central longitude */
  static char *border[2] = {"Western", "Eastern"};