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Clean up x0 calculation

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This commit is contained in:
Allan Bazinet 2024-10-26 06:31:47 -07:00
parent c98cefc500
commit df8deb5d0d
1 changed files with 18 additions and 4 deletions
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22
plotter.cpp
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@ -1,5 +1,7 @@
#include "plotter.h"
#include <algorithm>
#include <cmath>
#include <type_traits>
#include <utility>
#include <QDebug>
#include <QMouseEvent>
@ -41,6 +43,21 @@ namespace
constexpr std::size_t VERT_DIVS = 7;
// Given a floating point value, return the fractional portion of the
// value e.g., 42.7 -> 0.7.
template <typename T,
typename = std::enable_if_t<std::is_floating_point_v<T>>>
T
fractionalPart(T const v)
{
T integralPart;
return std::modf(v, &integralPart);
}
// Given the frequency span of the entire viewable plot region, return
// the frequency span that each division should occupy.
int
freqPerDiv(double const fSpan)
{
@ -357,10 +374,7 @@ CPlotter::drawOverlay()
float const ppdV = fpd / m_freqPerPixel;
float const ppdH = (float)m_h2 / VERT_DIVS;
std::size_t const hdivs = fSpan / fpd + 1.9999;
float xx0 = float(m_startFreq) / float(fpd);
xx0 = xx0 - int(xx0);
int x0 = xx0 * ppdV + 0.5;
auto const x0 = static_cast<int>(fractionalPart((double)m_startFreq / fpd) * ppdV + 0.5);
p.setPen(QPen(Qt::white, 1, Qt::DotLine));