Speed up analog trace painting

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

diff --git a/pv/view/analogsignal.cpp b/pv/view/analogsignal.cpp
index af979c0c2d8a6500358538138e2e89cc9adeccf6..4479885da72589eb678b45ad7f45d16830b8fc18 100644 (file)
--- a/pv/view/analogsignal.cpp
+++ b/pv/view/analogsignal.cpp
@@ -73,7 +73,8 @@ const QColor AnalogSignal::GridMinorColor = QColor(0, 0, 0, 20 * 256 / 100);
 
 const QColor AnalogSignal::SamplingPointColour(0x77, 0x77, 0x77);
 
-const float AnalogSignal::EnvelopeThreshold = 256.0f;
+const int64_t AnalogSignal::TracePaintBlockSize = 1024 * 1024;  // 4 MiB (due to float)
+const float AnalogSignal::EnvelopeThreshold = 64.0f;
 
 const int AnalogSignal::MaximumVDivs = 10;
 const int AnalogSignal::MinScaleIndex = -6;
@@ -309,6 +310,15 @@ void AnalogSignal::paint_trace(QPainter &p,
        int y, int left, const int64_t start, const int64_t end,
        const double pixels_offset, const double samples_per_pixel)
 {
+       if (end <= start)
+               return;
+
+       // Calculate and paint the sampling points if enabled and useful
+       GlobalSettings settings;
+       const bool show_sampling_points =
+               settings.value(GlobalSettings::Key_View_ShowSamplingPoints).toBool() &&
+               (samples_per_pixel < 0.25);
+
        p.setPen(base_->colour());
 
        const int64_t points_count = end - start;
@@ -316,38 +326,45 @@ void AnalogSignal::paint_trace(QPainter &p,
        QPointF *points = new QPointF[points_count];
        QPointF *point = points;
 
-       QRectF *const sampling_points = new QRectF[points_count];
+       QRectF *sampling_points = nullptr;
+       if (show_sampling_points)
+                sampling_points = new QRectF[points_count];
        QRectF *sampling_point = sampling_points;
 
-       pv::data::SegmentAnalogDataIterator* it =
-               segment->begin_sample_iteration(start);
+       int64_t sample_count = min(points_count, TracePaintBlockSize);
+       int64_t block_sample = 0;
+       const float *sample_block = segment->get_samples(start, start + sample_count);
 
        const int w = 2;
-       for (int64_t sample = start; sample != end; sample++) {
+       for (int64_t sample = start; sample != end; sample++, block_sample++) {
+
+               if (block_sample == TracePaintBlockSize) {
+                       block_sample = 0;
+                       delete[] sample_block;
+                       sample_count = min(points_count - sample, TracePaintBlockSize);
+                       sample_block = segment->get_samples(sample, sample + sample_count);
+               }
+
                const float x = (sample / samples_per_pixel -
                        pixels_offset) + left;
 
-               *point++ = QPointF(x, y - *((float*)it->value) * scale_);
-               *sampling_point++ = QRectF(x - (w / 2), y - *((float*)it->value) * scale_ - (w / 2), w, w);
+               *point++ = QPointF(x, y - sample_block[block_sample] * scale_);
 
-               segment->continue_sample_iteration(it, 1);
+               if (show_sampling_points)
+                       *sampling_point++ =
+                               QRectF(x - (w / 2), y - sample_block[block_sample] * scale_ - (w / 2), w, w);
        }
-       segment->end_sample_iteration(it);
+       delete[] sample_block;
 
        p.drawPolyline(points, points_count);
 
-       // Paint the sampling points if enabled
-       GlobalSettings settings;
-       const bool show_sampling_points =
-               settings.value(GlobalSettings::Key_View_ShowSamplingPoints).toBool();
-
-       if (show_sampling_points && (samples_per_pixel < 0.25)) {
+       if (show_sampling_points) {
                p.setPen(SamplingPointColour);
                p.drawRects(sampling_points, points_count);
+               delete[] sampling_points;
        }
 
        delete[] points;
-       delete[] sampling_points;
 }
 
 void AnalogSignal::paint_envelope(QPainter &p,