View: Do not emit superfluous signals in a loop

diff --git a/pv/view/view.cpp b/pv/view/view.cpp
index e00917f64fa4d49086890ce333d924ed76ad77fc..37cc94301ad24cd1c819108eb7ba66ab3459cf6d 100644 (file)
--- a/pv/view/view.cpp
+++ b/pv/view/view.cpp
@@ -557,6 +557,13 @@ void View::calculate_tick_spacing()
 
        QFontMetrics m(QApplication::font());
 
+       // Copies of the member variables with the same name, used in the calculation
+       // and written back afterwards, so that we don't emit signals all the time
+       // during the calculation.
+       pv::util::Timestamp tick_period = tick_period_;
+       pv::util::SIPrefix tick_prefix = tick_prefix_;
+       unsigned tick_precision = tick_precision_;
+
        do {
                const double min_period = scale_ * min_width;
 
@@ -577,19 +584,18 @@ void View::calculate_tick_spacing()
                                (ScaleUnits[unit++] + tp_margin);
                } while (tp_with_margin < min_period && unit < countof(ScaleUnits));
 
-               set_tick_period(order_decimal * ScaleUnits[unit - 1]);
-               set_tick_prefix(static_cast<pv::util::SIPrefix>(
-                       (order - pv::util::exponent(pv::util::SIPrefix::yocto)) / 3));
+               tick_period = order_decimal * ScaleUnits[unit - 1];
+               tick_prefix = static_cast<pv::util::SIPrefix>(
+                       (order - pv::util::exponent(pv::util::SIPrefix::yocto)) / 3);
 
                // Precision is the number of fractional digits required, not
                // taking the prefix into account (and it must never be negative)
-               set_tick_precision(std::max(
-                       ceil(log10(1 / tick_period_)).convert_to<int>(), 0));
+               tick_precision = std::max(ceil(log10(1 / tick_period)).convert_to<int>(), 0);
 
-               tick_period_width = (tick_period_ / scale_).convert_to<double>();
+               tick_period_width = (tick_period / scale_).convert_to<double>();
 
                const QString label_text =
-                       format_time(max_time, tick_prefix_, time_unit_, tick_precision_);
+                       format_time(max_time, tick_prefix, time_unit_, tick_precision);
 
                label_width = m.boundingRect(0, 0, INT_MAX, INT_MAX,
                        Qt::AlignLeft | Qt::AlignTop, label_text).width() +
@@ -597,6 +603,10 @@ void View::calculate_tick_spacing()
 
                min_width += SpacingIncrement;
        } while (tick_period_width < label_width);
+
+       set_tick_period(tick_period);
+       set_tick_prefix(tick_prefix);
+       set_tick_precision(tick_precision);
 }
 
 void View::update_scroll()