Improve (a little) the plotting of digital data with plot option digiplot:

Repair scaling on MS Windows:
Suppress y axis lettering and unit:
Allow or dis-allow grid.

src/frontend/plotting/grid.c

@@ -706,7 +706,7 @@ drawlingrid(GRAPH *graph, char *units, int spacing, int nsp, double dst, double
         j = (int)m;
         if (j == 0)
             SetLinestyle(0);
-        if (graph->grid.gridtype != GRID_NONE) {
+        if (graph->grid.gridtype != GRID_NONE && graph->grid.gridtype != GRID_DIGITAL_NONE) {
             if (axis == x_axis)
                 DevDrawLine(graph->viewportxoff + i,
                             graph->viewportyoff, graph->viewportxoff + i,
@@ -726,7 +726,7 @@ drawlingrid(GRAPH *graph, char *units, int spacing, int nsp, double dst, double
             DevDrawText(buf, graph->viewportxoff + i -
                         ((int) strlen(buf) * graph->fontwidth) / 2,
                         (int) (graph->fontheight * 2.5), 0);
-        else
+        else if (graph->grid.gridtype != GRID_DIGITAL && graph->grid.gridtype != GRID_DIGITAL_NONE)
             DevDrawText(buf, graph->viewportxoff - 2 -
                         graph->fontwidth * (int) strlen(buf),
                         graph->viewportyoff + i -
@@ -736,10 +736,12 @@ drawlingrid(GRAPH *graph, char *units, int spacing, int nsp, double dst, double
         if (nsp == 1)
             j += 1000;
     }
+    /* the x axis unit (bottom right) and the y axis unit (upper left) */
     if (!graph->nounits) {
         if (axis == x_axis)
             DevDrawText(units, (int)(graph->absolute.width * RELPOSXUNIT + unitshift), graph->fontheight, 0);
-        else
+        /* y axis unit only when no digitop plot */
+        else if (graph->grid.gridtype != GRID_DIGITAL && graph->grid.gridtype != GRID_DIGITAL_NONE)
             DevDrawText(units, graph->fontwidth,
                 (int)(graph->absolute.height - 2 * graph->fontheight), 0);
     }

src/frontend/plotting/plotit.c

@@ -852,29 +852,43 @@ bool plotit(wordlist *wl, const char *hcopy, const char *devname)
         }
     }
 
-    /* Add n * spacing (e.g. 1.3) to digital event node based vectors */
+    /* Add n * spacing (e.g. 1.5) to digital event node based vectors */
     if (digitop) {
         double spacing = 1.5;
         double nn = 0.;
-        int ii = 0;
+        int ii = 0, jj = 0;
+
         for (d = vecs; d; d = d->v_link2) {
             if (d->v_scale && eq(d->v_scale->v_name, "step") && (d->v_scale->v_type == SV_TIME) && (d->v_type == SV_VOLTAGE) && (d->v_length > 1)) {
                 for (ii = 0; ii < d->v_length; ii++) {
                     d->v_realdata[ii] += nn;
                 }
                 nn += spacing;
+                jj++ ;
             }
         }
         if (!ydelta)
             ydelta = TMALLOC(double, 1);
         *ydelta = spacing;
+        /* new plot */
         if (!ylim) {
             ylim = TMALLOC(double, 2);
             ylim[0] = 0;
-            ylim[1] = nn;
+            /* make ylim[1] a multiple of 2*1.5 */
+            if (jj % 2 == 0)
+                ylim[1] = nn;
+            else
+                ylim[1] = nn + 1.5;
         }
+        /* re-scaled plot */
         else {
-            if (ylim[0] < 1.5)
+            /* just figure out that ylim[0] < ylim[1] */
+            if (ylim[0] > ylim[1]) {
+                double interm = ylim[1];
+                ylim[1] = ylim[0];
+                ylim[0] = interm;
+            }
+            if (ylim[0] < 1.1)
             /* catch the bottom line */
                 ylim[0] = 0;
             else
@@ -882,6 +896,11 @@ bool plotit(wordlist *wl, const char *hcopy, const char *devname)
                 ylim[0] = ((int)(ylim[0] / spacing) + 1) * spacing;
             ylim[1] = ((int)(ylim[1] / spacing) + 1) * spacing;
         }
+        /* suppress y labeling */
+        if (gtype == GRID_NONE)
+            gtype = GRID_DIGITAL_NONE;
+        else
+            gtype = GRID_DIGITAL;
     }
 
     /* If there are higher dimensional vectors, transform them into a

src/include/ngspice/grid.h

@@ -7,8 +7,9 @@
 
    Note: SMITHGRID is only a smith grid, SMITH transforms the data */
 typedef enum {
-    GRID_NONE, GRID_LIN, GRID_LOGLOG, GRID_XLOG,
-    GRID_YLOG, GRID_POLAR, GRID_SMITH, GRID_SMITHGRID
+    GRID_NONE, GRID_LIN, GRID_LOGLOG, GRID_XLOG, GRID_YLOG,
+    GRID_POLAR, GRID_SMITH, GRID_SMITHGRID, GRID_DIGITAL_NONE,
+    GRID_DIGITAL
 } GRIDTYPE;
 
 void gr_fixgrid(GRAPH *graph, double xdelta, double ydelta, int xtype, int ytype);