View/Ruler: Calculate and use tick precision

[pulseview.git] / pv / view / view.cpp

diff --git a/pv/view/view.cpp b/pv/view/view.cpp
index 0844b6a47e6fd13c16d34ba85eddfc7850ec3974..032546dba034eda4cea63cc3f60489127cd28d9d 100644 (file)
--- a/pv/view/view.cpp
+++ b/pv/view/view.cpp
@@ -104,6 +104,7 @@ View::View(Session &session, QWidget *parent) :
        always_zoom_to_fit_(false),
        tick_period_(0.0),
        tick_prefix_(0),
+       tick_precision_(0),
        time_unit_(util::Time),
        show_cursors_(false),
        cursors_(new CursorPair(*this)),
@@ -236,6 +237,11 @@ unsigned int View::tick_prefix() const
        return tick_prefix_;
 }
 
+unsigned int View::tick_precision() const
+{
+       return tick_precision_;
+}
+
 double View::tick_period() const
 {
        return tick_period_;
@@ -490,7 +496,8 @@ void View::calculate_tick_spacing()
        const double SpacingIncrement = 32.0f;
        const double MinValueSpacing = 32.0f;
 
-       double min_width = SpacingIncrement, typical_width;
+       double min_width = SpacingIncrement;
+       double label_width, tick_period_width;
 
        QFontMetrics m(QApplication::font());
 
@@ -509,14 +516,22 @@ void View::calculate_tick_spacing()
 
                tick_prefix_ = (order - pv::util::FirstSIPrefixPower) / 3;
 
-               typical_width = m.boundingRect(0, 0, INT_MAX, INT_MAX,
-                       Qt::AlignLeft | Qt::AlignTop,
-                       format_time(offset_, tick_prefix_, time_unit_)).width() +
+               // Precision is the number of fractional digits required, not
+               // taking the prefix into account (and it must never be negative)
+               tick_precision_ = std::max((int)ceil(log10f(1 / tick_period_)), 0);
+
+               tick_period_width = tick_period_ / scale_;
+
+               const QString label_text =
+                       format_time(offset_, tick_prefix_, time_unit_, tick_precision_);
+
+               label_width = m.boundingRect(0, 0, INT_MAX, INT_MAX,
+                       Qt::AlignLeft | Qt::AlignTop, label_text).width() +
                                MinValueSpacing;
 
                min_width += SpacingIncrement;
 
-       } while (typical_width > tick_period_ / scale_);
+       } while (tick_period_width < label_width);
 }
 
 void View::update_scroll()