Fix bug and allow +apangle for decorated lines (#8182)

* Fix failure to honor +a angle in decorated lines

Simply did not pass the fixed angle when it was set and ended up passing the line angle which was zero.

* Fix bug and allow +apangle for decorated lines

This fixes the bug in #7591. While at it, we allow +apangle to let the symbol angle deviate by angle from the line's angle.+aangle still sets a fixed angle regardless of angle contortions.

doc/rst/source/explain_symbols.rst_

@@ -616,7 +616,8 @@
 
             **+a**\ *angle*
                 Force symbols at a fixed angle, **+an** for line-normal, or
-                **+ap** for line-parallel [Default].
+                **+ap** for line-parallel [Default]. Use **p**\ *angle* to set a
+                constant deviation from line-parallel.
 
             **+d**\ [*pen*]
                 Turn on debug, which will draw helper points and lines to illustrate

src/gmt_contour.h

@@ -41,7 +41,8 @@ enum GMT_enum_contline {
 enum GMT_enum_contangle {
 	GMT_ANGLE_LINE_PARALLEL = 0,	/* Angles follows the line locally */
 	GMT_ANGLE_LINE_NORMAL,	/* Angles is normal to the line locally */
-	GMT_ANGLE_LINE_FIXED};	/* Angle is fixed regardless of line direction */
+	GMT_ANGLE_LINE_FIXED,	/* Angle is fixed regardless of line direction */
+	GMT_ANGLE_LINE_DELTA};	/* Angle is a fixed offset from line direction */
 
 
 /*! Various settings for quoted line/contour label types */

src/gmt_decorate.h

@@ -54,7 +54,7 @@ struct GMT_DECORATE {
 	unsigned int nx;		/* Number of crossovers at any time */
 	unsigned int f_n;		/* Number of such points */
 	unsigned int nudge_flag;	/* 0 if off, 1 if nudging relative to x/y axis, 2 if following local line coordinate system */
-	unsigned int angle_type;	/* 0 = line-parallel (GMT_ANGLE_LINE_PARALLEL), 1 = line-normal (GMT_ANGLE_LINE_NORMAL), 2 = fixed angle (GMT_ANGLE_LINE_FIXED) */
+	unsigned int angle_type;	/* 0 = line-parallel (GMT_ANGLE_LINE_PARALLEL), 1 = line-normal (GMT_ANGLE_LINE_NORMAL), 2 = fixed angle (GMT_ANGLE_LINE_FIXED), 3 = fixed delta angle (GMT_ANGLE_LINE_DELTA) */
 	int number_placement;		/* How the n_cont symbols are distributed [-1/0/+1]*/
 	bool isolate;			/* true if we have a limit on how close symbols may appear (see below) */
 	bool segmentize;		/* true if we should segmentize input lines before plotting */

src/gmt_init.c

@@ -8592,7 +8592,8 @@ void gmt_label_syntax (struct GMT_CTRL *GMT, unsigned int indent, unsigned int k
 	}
 	else {
 		GMT_Usage (API, indent, "+a Place all %s at a fixed <angle>. "
-			"Or, specify +an (line-normal) or +ap (line-parallel) [Default].", feature[kind]);
+			"Or, specify +an (line-normal) or +ap (line-parallel) [Default]. If p<angle> is appended then
+				<angle> is used as a fixed deviation from the line orientation", feature[kind]);
 	}
 	if (kind < 2) GMT_Usage (API, indent, "+c Set clearance <dx>[/<dy>] between label and text box [15%%].");
 	GMT_Usage (API, indent, "+d Debug mode which draws helper points and lines; optionally add a pen [%s].", gmt_putpen (GMT, &GMT->current.setting.map_default_pen));

src/gmt_support.c

@@ -2233,6 +2233,12 @@ GMT_LOCAL void gmtsupport_line_angle_ave (struct GMT_CTRL *GMT, double x[], doub
 			if (fabs (L->line_angle - angle) > 145.0) L->line_angle += 180.0;
 		}
 	}
+	if (angle_type == GMT_ANGLE_LINE_DELTA) {	/* Add delta angle to line angle */
+		if (gmt_M_is_dnan (cangle)) /* Cannot use this angle - default to along-line angle */
+			angle_type = GMT_ANGLE_LINE_PARALLEL;
+		else
+			L->angle = L->line_angle + cangle;
+	}
 	if (angle_type == GMT_ANGLE_LINE_FIXED) {	/* Just return the fixed angle given (unless NaN) */
 		if (gmt_M_is_dnan (cangle)) /* Cannot use this angle - default to along-line angle */
 			angle_type = GMT_ANGLE_LINE_PARALLEL;
@@ -3387,6 +3393,7 @@ GMT_LOCAL void gmtsupport_hold_contour_sub (struct GMT_CTRL *GMT, double **xxx,
 /*! . */
 GMT_LOCAL void gmtsupport_add_decoration (struct GMT_CTRL *GMT, struct GMT_DATASEGMENT *S, struct GMT_LABEL *L, struct GMT_DECORATE *G) {
 	/* Add a symbol location to the growing segment */
+	double angle;
 	struct GMT_DATASEGMENT_HIDDEN *SH = gmt_get_DS_hidden (S);
 	if (S->n_rows == SH->n_alloc) {	/* Need more memory for the segment */
 		uint64_t col;
@@ -3411,7 +3418,10 @@ GMT_LOCAL void gmtsupport_add_decoration (struct GMT_CTRL *GMT, struct GMT_DATAS
 	S->data[GMT_X][S->n_rows] = L->x;
 	S->data[GMT_Y][S->n_rows] = L->y;
 	S->data[GMT_Z][S->n_rows] = gmt_M_to_inch (GMT, G->size);
-	S->data[3][S->n_rows] = L->line_angle;	/* Change this in inches internally instead of string */
+	if (G->angle_type == GMT_ANGLE_LINE_DELTA) angle = G->symbol_angle + L->line_angle;
+	else if (G->angle_type == GMT_ANGLE_LINE_FIXED) angle = G->symbol_angle;
+	else angle = L->line_angle;
+	S->data[3][S->n_rows] = angle;
 	S->text[S->n_rows++] = strdup (G->symbol_code);
 }
 
@@ -10959,8 +10969,16 @@ int gmtlib_decorate_specs (struct GMT_CTRL *GMT, char *txt, struct GMT_DECORATE
 	while ((gmt_strtok (specs, "+", &pos, p))) {
 		switch (p[0]) {
 			case 'a':	/* Angle specification */
-				if (p[1] == 'p' || p[1] == 'P')	/* Line-parallel label */
-					G->angle_type = GMT_ANGLE_LINE_PARALLEL;
+				if (p[1] == 'p' || p[1] == 'P')	{ /* Line-parallel label */
+					if (p[2]) {	/* Gave optional fixed angle deviation from line-parallel */
+						G->angle_type = GMT_ANGLE_LINE_DELTA;
+						G->symbol_angle = atof (&p[2]);
+						gmt_lon_range_adjust (GMT_IS_M180_TO_P180_RANGE, &G->symbol_angle);	/* Now -180/+180 */
+						while (fabs (G->symbol_angle) > 90.0) G->symbol_angle -= copysign (180.0, G->symbol_angle);
+					}
+					else
+						G->angle_type = GMT_ANGLE_LINE_PARALLEL;
+				}
 				else if (p[1] == 'n' || p[1] == 'N')	/* Line-normal label */
 					G->angle_type = GMT_ANGLE_LINE_NORMAL;
 				else {					/* Label at a fixed angle */

src/psxy.c

@@ -442,7 +442,7 @@ GMT_LOCAL int psxy_plot_decorations (struct GMT_CTRL *GMT, struct GMT_DATASET *D
 		return (GMT->parent->error);
 	tmp_file[len] = '.';	/* Restore the ".def" extension so we can delete the file (unless -Vd) */
 	if (gmt_M_is_verbose (GMT, GMT_MSG_DEBUG)) {	/* Leave the symbol def and txt files in the temp directory */
-		char tmp_file2[GMT_LEN64] = {""};
+		char tmp_file2[GMT_LEN128] = {""};
 		bool was = GMT->current.setting.io_header[GMT_OUT];	/* Save current setting */
 		GMT_Report (GMT->parent, GMT_MSG_DEBUG, "Temporary symbol file for decorated lines saved: %s\n", tmp_file);
 		if (GMT->parent->tmp_dir)	/* Make unique file in tmp dir */