Save any default CPT in hidden grid header

This addresses #6167 when we cut a subset from, sa, earth_relief_10m and then no longer know what the CPT should be.

Author: PaulWessel

src/gmt_dev.h

@@ -129,13 +129,13 @@ extern "C" {
 #include "gmt_common_math.h" /* Shared math functions */
 #include "gmt.h"             /* All GMT high-level API */
 #include "gmt_private.h"     /* API declaration needed by libraries */
+#include "gmt_constants.h"   /* All basic constant definitions */
 #include "gmt_hidden.h"      /* Hidden bookkeeping structure for API containers */
 
 struct GMT_CTRL; /* forward declaration of GMT_CTRL */
 
 #include "gmt_notposix.h"       /* Non-POSIX extensions */
 
-#include "gmt_constants.h"      /* All basic constant definitions */
 #include "gmt_modern.h"         /* Modern mode constant definitions */
 #include "gmt_macros.h"         /* All basic macros definitions */
 #include "gmt_dimensions.h"     /* Constant definitions created by configure */

src/gmt_hidden.h

@@ -159,6 +159,7 @@ struct GMT_GRID_HEADER_HIDDEN {
 	char name[GMT_GRID_NAME_LEN256]; /* Actual name of the file after any ?<varname> and =<stuff> has been removed */
 	char varname[GMT_GRID_VARNAME_LEN80];/* NetCDF: variable name */
 	char *title;					 /* Title string not limited to GMT_GRID_TITLE_LEN80 characters */
+	char cpt[GMT_LEN64]; 			 /* Name of default CPT for a remote grid subset written via grdcut */
 	char *command;					 /* Command/history string not limited to GMT_GRID_TITLE_LEN80 characters */
 	char *remark;					 /* Remark/description string not limited to GMT_GRID_REMARK_LEN160 characters */
 	int row_order;                   /* NetCDF: k_nc_start_south if S->N, k_nc_start_north if N->S */

src/gmt_io.c

@@ -4752,9 +4752,17 @@ int gmtlib_nc_get_att_vtext (struct GMT_CTRL *GMT, int ncid, int varid, char *na
 	size_t attlen, trunclen;
 	char *att = NULL;
 
+	if (name == NULL) {
+		GMT_Report (GMT->parent, GMT_MSG_ERROR, "Attribute name passed to gmtlib_nc_get_att_vtext is NULL\n");
+		return GMT_RUNTIME_ERROR;
+	}
+	if (text == NULL) {
+		GMT_Report (GMT->parent, GMT_MSG_ERROR, "Attribute pointer passed to gmtlib_nc_get_att_vtext is NULL\n");
+		return GMT_RUNTIME_ERROR;
+	}
 	status = nc_inq_attlen (ncid, varid, name, &attlen);
 	if (status != NC_NOERR) {	/* No such attribute */
-		*text = '\0';
+		text[0] = '\0';
 		return status;
 	}
 	att = calloc (attlen+1, sizeof (char));	/* Allocate the memory for the full string plus text terminator */
@@ -4782,8 +4790,8 @@ int gmtlib_nc_get_att_vtext (struct GMT_CTRL *GMT, int ncid, int varid, char *na
 		strncpy (text, att, trunclen); /* Copy att to text */
 		text[trunclen] = '\0'; /* Terminate string */
 	}
-	else	/* Not successful, set ouput string to empty */
-		*text = '\0';
+	else	/* Not successful, set output string to empty */
+		text[0] = '\0';
 	if (wipe) gmt_M_str_free (att);	/* Free since not placed in hidden structure */
 	return status;
 }

src/gmt_nc.c

@@ -896,6 +896,9 @@ GMT_LOCAL int gmtnc_grd_info (struct GMT_CTRL *GMT, struct GMT_GRID_HEADER *head
 			/* Valid range is already in packed units, so do not convert */
 			header->z_min = dummy[0], header->z_max = dummy[1];
 		}
+		if (gmtlib_nc_get_att_text (GMT, ncid, z_id, "cpt", HH->cpt, GMT_LEN64))	/* Found cpt attribute */
+			GMT_Report (GMT->parent, GMT_MSG_INFORMATION, "netCDF grid %s has a default CPT %s.\n", HH->cpt);
+
 		if (gmt_M_is_dnan (header->z_min) && gmt_M_is_dnan (header->z_max)) {
 			GMT_Report (GMT->parent, GMT_MSG_INFORMATION, "netCDF grid %s information has zmin = zmax = NaN. Reset to 0/0.\n", HH->name);
 			header->z_min = header->z_max = 0.0;
@@ -1029,6 +1032,8 @@ GMT_LOCAL int gmtnc_grd_info (struct GMT_CTRL *GMT, struct GMT_GRID_HEADER *head
 
 		/* Define z variable. Attempt to remove "scale_factor" or "add_offset" when no longer needed */
 		gmtnc_put_units (ncid, z_id, header->z_units);
+		if (GMT->parent->remote_info && GMT->parent->remote_id != GMT_NOTSET && GMT->parent->remote_info[GMT->parent->remote_id].CPT[0] != '-')	/* Subset of remote grid with default CPT, save name as an attribute */
+			gmt_M_err_trap (nc_put_att_text (ncid, z_id, "cpt", strlen (GMT->parent->remote_info[GMT->parent->remote_id].CPT), GMT->parent->remote_info[GMT->parent->remote_id].CPT));
 
 		if (header->z_scale_factor != 1.0) {
 			gmt_M_err_trap (nc_put_att_double (ncid, z_id, "scale_factor", NC_DOUBLE, 1U, &header->z_scale_factor));

src/gmt_private.h

@@ -209,6 +209,7 @@ struct GMTAPI_CTRL {
 	char *O_OPT, *K_OPT, *P_OPT, *c_OPT;
 	/* structure array of remote file information (sorted alphabetically) */
 	int n_remote_info;	/* How many remote server files we know of */
+	int remote_id;	/* Currently used remote ID or -1 */
 	struct GMT_DATA_INFO *remote_info;
 	bool server_announced;	/* Set to true after we have announced which GMT data server we are using */
 	struct GMT_COMMON *common_snapshot;	/* Holds the latest GMT common option settings after a module completes. */

src/gmt_prototypes.h

@@ -659,7 +659,7 @@ EXTERN_MSC int gmt_find_macro (char *arg, unsigned int n_macros, struct GMT_MATH
 EXTERN_MSC int gmt_load_macros (struct GMT_CTRL *GMT, char *mtype, struct GMT_MATH_MACRO **M);
 EXTERN_MSC struct GMT_OPTION * gmt_substitute_macros (struct GMT_CTRL *GMT, struct GMT_OPTION *options, char *mfile);
 EXTERN_MSC void gmt_free_macros (struct GMT_CTRL *GMT, unsigned int n_macros, struct GMT_MATH_MACRO **M);
-EXTERN_MSC char * gmt_cpt_default (struct GMTAPI_CTRL *API, char *cpt, char *file);
+EXTERN_MSC char * gmt_cpt_default (struct GMTAPI_CTRL *API, char *cpt, char *file, struct GMT_GRID_HEADER *h);
 EXTERN_MSC void gmt_sort_array (struct GMT_CTRL *GMT, void *base, uint64_t n, unsigned int type);
 EXTERN_MSC bool gmt_polygon_is_open (struct GMT_CTRL *GMT, double x[], double y[], uint64_t n);
 EXTERN_MSC int gmt_polygon_centroid (struct GMT_CTRL *GMT, double *x, double *y, uint64_t n, double *Cx, double *Cy);

src/gmt_remote.c

@@ -477,6 +477,7 @@ void gmt_set_unspecified_remote_registration (struct GMTAPI_CTRL *API, char **fi
 	ext = gmt_chop_ext (infile);
 	/* If the remote file is found then there is nothing to do */
 	if ((k_data = gmt_remote_dataset_id (API, infile)) == GMT_NOTSET) goto clean_up;
+	API->remote_id = k_data;
 	L = strlen (API->remote_info[k_data].dir) - 1;	/* Length of dir minus trailing slash */
 	strncpy (dir, API->remote_info[k_data].dir, L);	dir[L] = '\0';	/* Duplicate dir without slash */
 	p = strrchr (dir, '/') + 1;	/* Start of final subdirectory (skipping over the slash we found) */
@@ -498,6 +499,7 @@ void gmt_set_unspecified_remote_registration (struct GMTAPI_CTRL *API, char **fi
 			}
 			gmt_M_str_free (*file_ptr);
 			*file_ptr = strdup (newfile);
+			API->remote_id = k_data;
 			goto clean_up;
 		}
 	}

src/gmt_support.c

@@ -8337,7 +8337,7 @@ struct GMT_PALETTE * gmtlib_read_cpt (struct GMT_CTRL *GMT, void *source, unsign
 	return (X);
 }
 
-char * gmt_cpt_default (struct GMTAPI_CTRL *API, char *cpt, char *file) {
+char * gmt_cpt_default (struct GMTAPI_CTRL *API, char *cpt, char *file, struct GMT_GRID_HEADER *h) {
 	/* Return which type of default CPT this data set should use.
 	 * If cpt is specified then that is what we will use. If not, then
 	 * we determine if file is a remote data set, and if it is and has a
@@ -8346,9 +8346,11 @@ char * gmt_cpt_default (struct GMTAPI_CTRL *API, char *cpt, char *file) {
 	int k_data;
 	static char *srtm_cpt = "srtm";
 	char *curr_cpt = NULL;
+	struct GMT_GRID_HEADER_HIDDEN *HH = gmt_get_H_hidden (h);
 
 	if (cpt) return strdup (cpt);	/* CPT was already specified */
 	if (file == NULL) return NULL;	/* No file given, so there */
+	if (HH->cpt[0] && HH->cpt[0] != '-') return (strdup (HH->cpt));	/* Found it in the grid header */
 	if (API->GMT->current.setting.run_mode == GMT_MODERN && (curr_cpt = gmt_get_current_item (API->GMT, "cpt", false))) return curr_cpt;	/* Use current CPT */
 
 	if ((k_data = gmt_remote_dataset_id (API, file)) == GMT_NOTSET) {

src/grd2kml.c

@@ -695,7 +695,7 @@ EXTERN_MSC int GMT_grd2kml (void *V_API, int mode, void *args) {
 	}
 
 	if (!Ctrl->C.active || gmt_is_cpt_master (GMT, Ctrl->C.file)) {	/* If no cpt given or just a master then we must compute a scaled one from the full-size grid and use it throughout */
-		char *cpt = gmt_cpt_default (API, Ctrl->C.file, Ctrl->In.file);
+		char *cpt = gmt_cpt_default (API, Ctrl->C.file, Ctrl->In.file, G->header);
 		char cptfile[PATH_MAX] = {""};
 		struct GMT_PALETTE *P = NULL;
 		if ((P = gmt_get_palette (GMT, cpt, GMT_CPT_OPTIONAL, G->header->z_min, G->header->z_max, Ctrl->C.dz)) == NULL) {

src/grdimage.c

@@ -1581,7 +1581,7 @@ EXTERN_MSC int GMT_grdimage (void *V_API, int mode, void *args) {
 	has_content = (got_z_grid) ? false : true;	/* Images always have content but grids may be all NaN */
 	if (got_z_grid) {	/* Got a single grid so need to convert z to color via a CPT */
 		if (Ctrl->C.active) {	/* Read a palette file */
-			char *cpt = gmt_cpt_default (API, Ctrl->C.file, Ctrl->In.file);
+			char *cpt = gmt_cpt_default (API, Ctrl->C.file, Ctrl->In.file, Grid_orig->header);
 			if ((P = gmt_get_palette (GMT, cpt, GMT_CPT_OPTIONAL, Grid_orig->header->z_min, Grid_orig->header->z_max, Ctrl->C.dz)) == NULL) {
 				GMT_Report (API, GMT_MSG_ERROR, "Failed to read CPT %s.\n", Ctrl->C.file);
 				gmt_free_header (API->GMT, &header_G);

src/grdview.c

@@ -979,7 +979,7 @@ EXTERN_MSC int GMT_grdview (void *V_API, int mode, void *args) {
 
 	if (Ctrl->C.active) {
 		char *dataset_cpt = (Ctrl->G.active && Ctrl->G.n == 1 && !gmt_M_file_is_image (Ctrl->G.file[0])) ? Ctrl->G.file[0] : Ctrl->In.file;
-		char *cpt = gmt_cpt_default (API, Ctrl->C.file, dataset_cpt);
+		char *cpt = gmt_cpt_default (API, Ctrl->C.file, dataset_cpt, Topo->header);
 		if ((P = gmt_get_palette (GMT, cpt, GMT_CPT_OPTIONAL, Topo->header->z_min, Topo->header->z_max, Ctrl->C.dz)) == NULL) {
 			Return (API->error);
 		}