Provide short-term fix for #627 by limiting zoom range to 100 ps

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

diff --git a/pv/view/view.cpp b/pv/view/view.cpp
index 0844b6a47e6fd13c16d34ba85eddfc7850ec3974..fdb9354b9315cefe4c4a06d23b00a879db7bab82 100644 (file)
--- a/pv/view/view.cpp
+++ b/pv/view/view.cpp
@@ -84,7 +84,7 @@ namespace pv {
 namespace view {
 
 const double View::MaxScale = 1e9;
-const double View::MinScale = 1e-15;
+const double View::MinScale = 1e-12;
 
 const int View::MaxScrollValue = INT_MAX / 2;
 const int View::MaxViewAutoUpdateRate = 25; // No more than 25 Hz with sticky scrolling
@@ -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_;
@@ -487,10 +493,16 @@ void View::set_zoom(double scale, int offset)
 
 void View::calculate_tick_spacing()
 {
-       const double SpacingIncrement = 32.0f;
-       const double MinValueSpacing = 32.0f;
+       const double SpacingIncrement = 10.0f;
+       const double MinValueSpacing = 25.0f;
+
+       // Figure out the highest numeric value visible on a label
+       const QSize areaSize = viewport_->size();
+       const double max_time = max(fabs(offset_),
+               fabs(offset_ + scale_ * areaSize.width()));
 
-       double min_width = SpacingIncrement, typical_width;
+       double min_width = SpacingIncrement;
+       double label_width, tick_period_width;
 
        QFontMetrics m(QApplication::font());
 
@@ -500,23 +512,37 @@ void View::calculate_tick_spacing()
                const int order = (int)floorf(log10f(min_period));
                const double order_decimal = pow(10.0, order);
 
+               // Allow for a margin of error so that a scale unit of 1 can be used.
+               // Otherwise, for a SU of 1 the tick period will almost always be below
+               // the min_period by a small amount - and thus skipped in favor of 2.
+               // Note: margin assumes that SU[0] and SU[1] contain the smallest values
+               double tp_margin = (ScaleUnits[0] + ScaleUnits[1]) / 2.0;
+               double tp_with_margin;
                unsigned int unit = 0;
 
                do {
-                       tick_period_ = order_decimal * ScaleUnits[unit++];
-               } while (tick_period_ < min_period &&
-                       unit < countof(ScaleUnits));
+                       tp_with_margin = order_decimal * (ScaleUnits[unit++] + tp_margin);
+               } while (tp_with_margin < min_period && unit < countof(ScaleUnits));
 
+               tick_period_ = order_decimal * ScaleUnits[unit - 1];
                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(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() +
                                MinValueSpacing;
 
                min_width += SpacingIncrement;
 
-       } while (typical_width > tick_period_ / scale_);
+       } while (tick_period_width < label_width);
 }
 
 void View::update_scroll()