+std::pair<double, unsigned int> Ruler::calculate_tick_spacing(
+ QPainter& p, double scale, double offset)
+{
+ const double SpacingIncrement = 32.0f;
+ const double MinValueSpacing = 32.0f;
+
+ double min_width = SpacingIncrement, typical_width;
+
+ double tick_period;
+ unsigned int prefix;
+
+ do {
+ const double min_period = scale * min_width;
+
+ const int order = (int)floorf(log10f(min_period));
+ const double order_decimal = pow(10.0, order);
+
+ unsigned int unit = 0;
+
+ do {
+ tick_period = order_decimal * ScaleUnits[unit++];
+ } while (tick_period < min_period && unit < countof(ScaleUnits));
+
+ prefix = (order - pv::util::FirstSIPrefixPower) / 3;
+
+ typical_width = p.boundingRect(0, 0, INT_MAX, INT_MAX,
+ AlignLeft | AlignTop, pv::util::format_time(offset,
+ prefix)).width() + MinValueSpacing;
+
+ min_width += SpacingIncrement;
+
+ } while(typical_width > tick_period / scale);
+
+ return std::make_pair(tick_period, prefix);
+}
+