comparison base/ScaleTickIntervals.h @ 1411:1f0d071e7ce6 scale-ticks

More tests & fixes

 
 #include <string>
 #include <vector>
 #include <cmath>
 
+//#define DEBUG_SCALE_TICK_INTERVALS 1
+
+#ifdef DEBUG_SCALE_TICK_INTERVALS
 #include <iostream>
-
+#endif
 
 class ScaleTickIntervals
 {
 public:
     struct Range {
 	double min;        // start of value range
 	double max;        // end of value range
-	int n;             // number of divisions requested (will be n+1 ticks)
+	int n;             // number of divisions (will be at most n+1 ticks)
     };
 
     struct Tick {
 	double value;      // value this tick represents
 	std::string label; // value as written 

 	    return linear({ r.max, r.min, r.n });
 	}
 	
 	double inc = (r.max - r.min) / r.n;
 	if (inc == 0) {
-	    Ticks t { r.min, 1.0, r.min, false, 1, {} };
+#ifdef DEBUG_SCALE_TICK_INTERVALS
+            std::cerr << "inc == 0, using trivial range" << std::endl;
+#endif
+            double roundTo = r.min;
+            if (roundTo <= 0.0) {
+                roundTo = 1.0;
+            }
+	    Ticks t { r.min, 1.0, roundTo, true, 1, {} };
 	    explode(r, t);
 	    return t;
 	}
 
         double digInc = log10(inc);

             }
         } else {
             prec = precRange;
         }
 
+	double roundTo = pow(10.0, precInc);
+
+#ifdef DEBUG_SCALE_TICK_INTERVALS
         std::cerr << "\nmin = " << r.min << ", max = " << r.max << ", n = " << r.n
                   << ", inc = " << inc << std::endl;
         std::cerr << "digMax = " << digMax << ", digInc = " << digInc
                   << std::endl;
         std::cerr << "fixed = " << fixed << ", inc = " << inc
                   << ", precInc = " << precInc << ", precRange = " << precRange
                   << ", prec = " << prec << std::endl;
-
-	double roundTo = pow(10.0, precInc);
-
         std::cerr << "roundTo = " << roundTo << std::endl;
+#endif
         
 	inc = round(inc / roundTo) * roundTo;
         if (inc < roundTo) inc = roundTo;
         
 	double min = ceil(r.min / roundTo) * roundTo;

 	return t;
     }
 
 private:
     static void explode(const Range &r, Ticks &t) {
+#ifdef DEBUG_SCALE_TICK_INTERVALS
 	std::cerr << "initial = " << t.initial << ", spacing = " << t.spacing
 		  << ", roundTo = " << t.roundTo << ", fixed = " << t.fixed
 		  << ", precision = " << t.precision << std::endl;
+#endif
 	auto makeTick = [&](double value) {
 	    const int buflen = 40;
 	    char buffer[buflen];
 	    snprintf(buffer, buflen,
 		     t.fixed ? "%.*f" : "%.*e",
 		     t.precision, value);
 	    return Tick({ value, std::string(buffer) });
 	};
-	for (double value = t.initial;
-             value < r.max + t.spacing/2;
-             value += t.spacing) {
+        double eps = 1e-7;
+        if (t.spacing < eps * 10.0) {
+            eps = t.spacing / 10.0;
+        }
+	for (double value = t.initial; value < r.max + eps; value += t.spacing) {
 	    value = t.roundTo * round(value / t.roundTo);
 	    t.ticks.push_back(makeTick(value));
 	}
     }
 };