From: Soeren Apel <redacted>
Date: Mon, 10 Aug 2015 07:26:43 +0000 (+0200)
Subject: View/Ruler: Calculate and use tick precision
X-Git-Tag: pulseview-0.3.0~146
X-Git-Url: https://sigrok.org/gitweb/?p=pulseview.git;a=commitdiff_plain;h=d40f4db76fc8120fcd54ace8c6fce63387e025ca

View/Ruler: Calculate and use tick precision
---

diff --git a/pv/view/ruler.cpp b/pv/view/ruler.cpp
index 3ec75fc3..dfe7d1c5 100644
--- a/pv/view/ruler.cpp
+++ b/pv/view/ruler.cpp
@@ -91,7 +91,6 @@ void Ruler::paintEvent(QPaintEvent*)
 	p.setRenderHint(QPainter::Antialiasing);
 
 	const double tick_period = view_.tick_period();
-	const unsigned int prefix = view_.tick_prefix();
 
 	// Draw the tick marks
 	p.setPen(palette().color(foregroundRole()));
@@ -122,7 +121,8 @@ void Ruler::paintEvent(QPaintEvent*)
 			// Draw a major tick
 			p.drawText(x, ValueMargin, 0, text_height,
 				AlignCenter | AlignTop | TextDontClip,
-				util::format_time(t, prefix, view_.time_unit()));
+				util::format_time(t, view_.tick_prefix(), view_.time_unit(),
+					view_.tick_precision()));
 			p.drawLine(QPointF(x, major_tick_y1),
 				QPointF(x, ruler_height));
 		}
diff --git a/pv/view/view.cpp b/pv/view/view.cpp
index 0844b6a4..032546db 100644
--- 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()
diff --git a/pv/view/view.hpp b/pv/view/view.hpp
index 95a02084..ff7795c5 100644
--- a/pv/view/view.hpp
+++ b/pv/view/view.hpp
@@ -125,6 +125,11 @@ public:
 	 */
 	unsigned int tick_prefix() const;
 
+	/**
+	 * Returns the number of fractional digits shown for the time markings.
+	 */
+	unsigned int tick_precision() const;
+
 	/**
 	 * Returns period of the graticule time markings.
 	 */
@@ -315,6 +320,7 @@ private:
 
 	double tick_period_;
 	unsigned int tick_prefix_;
+	unsigned int tick_precision_;
 	util::TimeUnit time_unit_;
 
 	bool show_cursors_;