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Keep center frequency when changing FFT size #192

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Keep center frequency when changing FFT size #192

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9 changes: 9 additions & 0 deletions src/plotview.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -425,13 +425,17 @@ void PlotView::setCursorSegments(int segments)
selectedSamples.maximum = selectedSamples.minimum + (segments * sampPerSeg + 0.5f);

cursors.setSegments(segments);

updateView();
emitTimeSelection();
}

void PlotView::setFFTAndZoom(int size, int zoom)
{
auto oldSamplesPerColumn = samplesPerColumn();
float oldPlotCenter = (verticalScrollBar()->value() + viewport()->height() / 2.0) / plotsHeight();
if (verticalScrollBar()->maximum() == 0)
oldPlotCenter = 0.5;

// Set new FFT size
fftSize = size;
Expand All @@ -448,6 +452,10 @@ void PlotView::setFFTAndZoom(int size, int zoom)
horizontalScrollBar()->setPageStep(100);

updateView(true, samplesPerColumn() < oldSamplesPerColumn);

// maintain the relative position of the vertical scroll bar
if (verticalScrollBar()->maximum())
verticalScrollBar()->setValue((int )(oldPlotCenter * plotsHeight() - viewport()->height() / 2.0 + 0.5f));
}

void PlotView::setPowerMin(int power)
Expand Down Expand Up @@ -604,6 +612,7 @@ void PlotView::updateView(bool reCenter, bool expanding)
}
horizontalScrollBar()->setMaximum(std::max(0, sampleToColumn(mainSampleSource->count()) - width()));
verticalScrollBar()->setMaximum(std::max(0, plotsHeight() - viewport()->height()));

if (expanding) {
updateViewRange(reCenter);
}
Expand Down