Add inverted triangle to front symbol choices (#5983)

* Add inverted triangle to front options

This adds +v for inverted triangle as a new symbol.

* Update front.ps

* Update docs

* Update explain_symbols.rst_

doc/rst/source/explain_symbols.rst_

@@ -318,7 +318,7 @@
         plotted centered or as a half-symbols on one side.  Special options exist for indicating
         motion (e.g., faults) along a line.
 
-    **-Sf**\ [±]\ *gap*\ [/*size*][**+l**\|\ **+r**][**+b**\|\ **+c**\|\ **+f**\|\ **+s**\ [*angle*]\ \|\ **+t**][**+o**\ *offset*][**+p**\ [*pen*]].
+    **-Sf**\ [±]\ *gap*\ [/*size*][**+l**\|\ **+r**][**+b**\|\ **c**\|\ **f**\|\ **s**\ [*angle*]\ \|\ **t**\ \|\ **v**][**+o**\ *offset*][**+p**\ [*pen*]].
         Draw a **f**\ ront. Supply distance *gap* between symbols and symbol *size*.
         If *gap* is negative, it is interpreted to mean the *number* of symbols along the
         front instead. If *gap* has a leading + then we use the value exactly as given
@@ -327,7 +327,7 @@
         and *size* is thus required.  Append **+l** or **+r** to plot symbols on the left or
         right side of the front [Default is centered]. Append **+**\ *type* to
         specify which symbol to plot: **b**\ ox, **c**\ ircle, **f**\ ault,
-        **s**\ lip, or **t**\ riangle. [Default is **f**\ ault]. Slip means
+        **s**\ lip, **t**\ riangle or in\ **v**\ erted triangle. [Default is **f**\ ault]. Slip means
         left-lateral or right-lateral strike-slip arrows (centered is not an
         option). The **+s** modifier optionally accepts the angle used to draw
         the vector [20]. Alternatively, use **+S** which draws arcuate arrow

doc/scripts/GMT_base_symbols7.sh

@@ -18,4 +18,5 @@ gmt psxy -R -J -O -K -W1p -Gred -Sf-1/0.1i+b -X0.6i t.txt >> $ps
 gmt psxy -R -J -O -K -W1p -Gred -Sf-1/0.1i+c -X0.6i t.txt >> $ps
 gmt psxy -R -J -O -K -W1p -Gred -Sf-1/0.1i+f -X0.6i t.txt >> $ps
 gmt psxy -R -J -O -K -W1p -Sf-1/0.4i+S+l -X0.6i t.txt >> $ps
-gmt psxy -R -J -O -W1p -Glightorange -Sf-1/0.1i+t -X0.6i t.txt >> $ps
+gmt psxy -R -J -O -K -W1p -Glightorange -Sf-1/0.1i+t -X0.6i t.txt >> $ps
+gmt psxy -R -J -O -W1p -Glightgreen -Sf-1/0.1i+v -X0.6i t.txt >> $ps

src/gmt_init.c

@@ -5761,7 +5761,7 @@ GMT_LOCAL int gmtinit_parse_front (struct GMT_CTRL *GMT, char *text, struct GMT_
 	char p[GMT_BUFSIZ] = {""}, txt_a[GMT_LEN256] = {""}, txt_b[GMT_LEN256] = {""};
 
 	/* text[0] is the leading 'f' for front */
-	if (text[1] == '+' && !strchr ("bcfilrsStop", text[2])) S->f.f_exact = true, k0 = 2;	/* Special leading + to be skipped when looking for modifiers */
+	if (text[1] == '+' && !strchr ("bcfilrsStopv", text[2])) S->f.f_exact = true, k0 = 2;	/* Special leading + to be skipped when looking for modifiers */
 	for (k = k0; text[k] && text[k] != '+'; k++);	/* Either find the first plus or run out or chars */
 	strncpy (p, text, k); p[k] = 0;
 	mods = (text[k] == '+');
@@ -5794,6 +5794,7 @@ GMT_LOCAL int gmtinit_parse_front (struct GMT_CTRL *GMT, char *text, struct GMT_
 					S->f.f_angle = (p[1]) ? atof (&p[1]) : 40.0;	/* Set curved slip arrow angle [40] */
 					break;
 			case 't':	S->f.f_symbol = GMT_FRONT_TRIANGLE;	break;	/* Triangle front */
+			case 'v':	S->f.f_symbol = GMT_FRONT_ITRIANGLE;	break;	/* Inverted triangle front */
 			case 'o':	S->f.f_off = gmt_M_to_inch (GMT, &p[1]);	break;	/* Symbol offset along line */
 			case 'p':	if (p[1]) {	/* Get alternate pen for front-symbol outline [-W] */
 						if (gmt_getpen (GMT, &p[1], &S->f.pen)) {

src/gmt_plot.c

@@ -9845,12 +9845,15 @@ void gmt_geo_rectangle (struct GMT_CTRL *GMT, double lon, double lat, double wid
 	PSL_plotsymbol (PSL, xp, yp, dim, PSL_ROTRECT);
 }
 
+#define M_PI_3          1.047197551196598	/* 60 degrees in radians */
+
 void gmt_draw_front (struct GMT_CTRL *GMT, double x[], double y[], uint64_t n, struct GMT_FRONTLINE *f) {
 	int ngap, tmp_join = 0, tmp_limit = 0;
 	bool skip;
 	uint64_t i;
-	double *s = NULL, xx[4], yy[4], dist = 0.0, w, frac, dx, dy, angle, dir1, dir2;
+	double *s = NULL, xx[6], yy[6], dist = 0.0, w, frac, dx, dy, angle, dir1, dir2;
 	double gap, x0, y0, xp, yp, len2, len3, len4, cosa, sina, sa, ca, offx, offy, dim[PSL_MAX_DIMS];
+	double a1, a2, sina1, sina2, cosa1, cosa2;
 	struct PSL_CTRL *PSL= GMT->PSL;
 
 	if (n < 2) return;
@@ -9960,6 +9963,38 @@ void gmt_draw_front (struct GMT_CTRL *GMT, double x[], double y[], uint64_t n, s
 					}
 					break;
 
+				case GMT_FRONT_ITRIANGLE:    /* Inverted triangle */
+					a1 = angle + M_PI_3;	a2 = a1 + M_PI_3;
+					sincos (a1, &sina1, &cosa1);
+					sincos (a2, &sina2, &cosa2);
+					switch (f->f_sense) {
+						case GMT_FRONT_CENTERED:
+							xx[0] = x0 + f->f_len * cosa1;   /* UR */
+							yy[0] = y0 + f->f_len * sina1;
+							xx[1] = x0 + f->f_len * cosa2;   /* UL */
+							yy[1] = y0 + f->f_len * sina2;
+							xx[2] = x0;   yy[2] = y0; 		 /* MC */
+							xx[3] = x0 - f->f_len * cosa1;   /* LR */
+							yy[3] = y0 - f->f_len * sina1;
+							xx[4] = x0 - f->f_len * cosa2;   /* LL */
+							yy[4] = y0 - f->f_len * sina2;
+							xx[5] = x0;   yy[5] = y0; 		 /* MC */
+							PSL_plotpolygon (PSL, xx, yy, 6);
+							break;
+						case GMT_FRONT_RIGHT:
+							sina1 = -sina1;	cosa1 = -cosa1;	sina2 = -sina2;	cosa2 = -cosa2;
+							/* Intentionally fall through - after changing the angle */
+						case GMT_FRONT_LEFT:
+							xx[0] = x0 + f->f_len * cosa1;   /* UR */
+							yy[0] = y0 + f->f_len * sina1;
+							xx[1] = x0 + f->f_len * cosa2;   /* UL */
+							yy[1] = y0 + f->f_len * sina2;
+							xx[2] = x0;   yy[2] = y0; 		 /* MC */
+							PSL_plotpolygon (PSL, xx, yy, 3);
+							break;
+					}
+					break;
+
 				case GMT_FRONT_CIRCLE:	/* Circles */
 					switch (f->f_sense) {
 						case GMT_FRONT_CENTERED:

src/gmt_plot.h

@@ -64,6 +64,7 @@
 /*! FRONT symbols */
 
 enum GMT_enum_front {GMT_FRONT_FAULT = 0,
+	GMT_FRONT_ITRIANGLE,
 	GMT_FRONT_TRIANGLE,
 	GMT_FRONT_SLIP,
 	GMT_FRONT_SLIPC,

src/psxy.c

@@ -619,7 +619,7 @@ static int usage (struct GMTAPI_CTRL *API, int level) {
 		"Append any of the units in %s to the dimensions [Default is k]. "
 		"For linear projection and -SJ we scale dimensions by the map scale.", GMT_LINE_BULLET, mod_name, GMT_LEN_UNITS_DISPLAY);
 
-	GMT_Usage (API, 2, "\n%s Front: -Sf<spacing>[/<ticklen>][+r+l][+f+t+s+c+b][+o<offset>][+p<pen>]", GMT_LINE_BULLET);
+	GMT_Usage (API, 2, "\n%s Front: -Sf<spacing>[/<ticklen>][+r|l][+f|t|s|c|b|v][+o<offset>][+p<pen>]", GMT_LINE_BULLET);
 	GMT_Usage (API, -3, "If <spacing> is negative it means the number of gaps instead. "
 		"If <spacing> has a leading + then <spacing> is used exactly [adjusted to fit line length]. "
 		"If not given, <ticklen> defaults to 15%% of <spacing>.  Append various modifiers:");
@@ -631,10 +631,11 @@ static int usage (struct GMTAPI_CTRL *API, int level) {
 	GMT_Usage (API, 3, "+f Plot centered cross-tick or tick only in specified direction [Default].");
 	GMT_Usage (API, 3, "+s Plot left-or right-lateral strike-slip arrows. Optionally append the arrow angle [20].");
 	GMT_Usage (API, 3, "+S Same as +s but with curved arrow-heads.");
-	GMT_Usage (API, 3, "+t diagonal square when centered, directed triangle otherwise.");
+	GMT_Usage (API, 3, "+t Plot diagonal square when centered, directed triangle otherwise.");
 	GMT_Usage (API, 3, "+o Plot first symbol when along-front distance is <offset> [0].");
 	GMT_Usage (API, 3, "+p Append <pen> for front symbol outline; if no <pen> then no outline [Outline with -W pen].");
-	GMT_Usage (API, -3, "Only one of +b|c|f|i|s|S|t may be selected.");
+	GMT_Usage (API, 3, "+v Plot two inverted triangles, directed inverted triangle otherwise.");
+	GMT_Usage (API, -3, "Only one of +b|c|f|i|s|S|t|v may be selected.");
 
 	GMT_Usage (API, 2, "\n%s Kustom: -Sk|K<symbolname>[/<size>]", GMT_LINE_BULLET);
 	GMT_Usage (API, -3, "Append <symbolname> immediately after 'k|K'; this will look for "

test/psxy/front.sh

@@ -4,7 +4,7 @@
 
 ps=front.ps
 
-gmt psbasemap -R0/6/0/8 -Jx1i -P -B0 -K -Xc > $ps
+gmt psbasemap -R0/7/0/8 -Jx1i -P -B0 -K -X0.5i > $ps
 cat << EOF > t.txt
 0	0
 10	20
@@ -15,30 +15,36 @@ gmt psxy -R -J -O -K -W1p -Gred -Sf0.4i/0.1i+c -X0.5i t.txt >> $ps
 gmt psxy -R -J -O -K -W1p -Gred -Sf0.4i/0.1i+f -X0.5i t.txt >> $ps
 gmt psxy -R -J -O -K -W1p -Sf0.6i/0.3i+S+r -X0.5i t.txt >> $ps
 gmt psxy -R -J -O -K -W1p -Gred -Sf0.4i/0.1i+t -X0.5i t.txt >> $ps
+gmt psxy -R -J -O -K -W1p -Gred -Sf0.4i/0.1i+v -X0.5i t.txt >> $ps
 gmt psxy -R -J -O -K -W1p -Gred -Sf-1/0.1i+b -X0.5i t.txt >> $ps
 gmt psxy -R -J -O -K -W1p -Gred -Sf-1/0.1i+c -X0.5i t.txt >> $ps
 gmt psxy -R -J -O -K -W1p -Gred -Sf-1/0.1i+f -X0.5i t.txt >> $ps
 gmt psxy -R -J -O -K -W1p -Sf-1/0.4i+S+l -X0.5i t.txt >> $ps
 gmt psxy -R -J -O -K -W1p -Gred -Sf-1/0.1i+t -X0.5i t.txt >> $ps
-# Right symbols using fixed interval, then same with just 1 centered symbol
-gmt psxy -R -J -O -K -W1p -Gblue -Sf0.4i/0.1i+b+r -X-4.5i -Y2.5i t.txt >> $ps
+gmt psxy -R -J -O -K -W1p -Gred -Sf-1/0.1i+v -X0.5i t.txt >> $ps
+# Right symbols using fixed interval, then same with just 1 right-side symbol
+gmt psxy -R -J -O -K -W1p -Gblue -Sf0.4i/0.1i+b+r -X-5.5i -Y2.5i t.txt >> $ps
 gmt psxy -R -J -O -K -W1p -Gblue -Sf0.4i/0.1i+c+r -X0.5i t.txt >> $ps
 gmt psxy -R -J -O -K -W1p -Gblue -Sf0.4i/0.1i+f+r -X0.5i t.txt >> $ps
 gmt psxy -R -J -O -K -W1p -Gblue -Sf0.6i/0.3i+s+r -X0.5i t.txt >> $ps
 gmt psxy -R -J -O -K -W1p -Gblue -Sf0.4i/0.1i+t+r -X0.5i t.txt >> $ps
+gmt psxy -R -J -O -K -W1p -Gblue -Sf0.4i/0.1i+v+r -X0.5i t.txt >> $ps
 gmt psxy -R -J -O -K -W1p -Gblue -Sf-1/0.1i+b+r -X0.5i t.txt >> $ps
 gmt psxy -R -J -O -K -W1p -Gblue -Sf-1/0.1i+c+r -X0.5i t.txt >> $ps
 gmt psxy -R -J -O -K -W1p -Gblue -Sf-1/0.1i+f+r -X0.5i t.txt >> $ps
 gmt psxy -R -J -O -K -W1p -Gblue -Sf-1/0.4i+s+r -X0.5i t.txt >> $ps
 gmt psxy -R -J -O -K -W1p -Gblue -Sf-1/0.1i+t+r -X0.5i t.txt >> $ps
-# Left symbols using fixed interval, then same with just 1 centered symbol
-gmt psxy -R -J -O -K -W1p -Gyellow -Sf0.4i/0.1i+b+l -X-4.5i -Y2.5i t.txt >> $ps
+gmt psxy -R -J -O -K -W1p -Gblue -Sf-1/0.1i+v+r -X0.5i t.txt >> $ps
+# Left symbols using fixed interval, then same with just 1 left-side symbol
+gmt psxy -R -J -O -K -W1p -Gyellow -Sf0.4i/0.1i+b+l -X-5.5i -Y2.5i t.txt >> $ps
 gmt psxy -R -J -O -K -W1p -Gyellow -Sf0.4i/0.1i+c+l -X0.5i t.txt >> $ps
 gmt psxy -R -J -O -K -W1p -Gyellow -Sf0.4i/0.1i+f+l -X0.5i t.txt >> $ps
 gmt psxy -R -J -O -K -W1p -Gyellow -Sf0.6i/0.3i+s+l -X0.5i t.txt >> $ps
 gmt psxy -R -J -O -K -W1p -Gyellow -Sf0.4i/0.1i+t+l -X0.5i t.txt >> $ps
+gmt psxy -R -J -O -K -W1p -Gyellow -Sf0.4i/0.1i+v+l -X0.5i t.txt >> $ps
 gmt psxy -R -J -O -K -W1p -Gyellow -Sf-1/0.1i+b+l -X0.5i t.txt >> $ps
 gmt psxy -R -J -O -K -W1p -Gyellow -Sf-1/0.1i+c+l -X0.5i t.txt >> $ps
 gmt psxy -R -J -O -K -W1p -Gyellow -Sf-1/0.1i+f+l -X0.5i t.txt >> $ps
 gmt psxy -R -J -O -K -W1p -Gyellow -Sf-1/0.4i+s+l -X0.5i t.txt >> $ps
-gmt psxy -R -J -O -W1p -Gyellow -Sf-1/0.1i+t+l -X0.5i t.txt >> $ps
+gmt psxy -R -J -O -K -W1p -Gyellow -Sf-1/0.1i+t+l -X0.5i t.txt >> $ps
+gmt psxy -R -J -O -W1p -Gyellow -Sf-1/0.1i+v+l -X0.5i t.txt >> $ps