improved perfs and event management

src/event_store.cpp

@@ -13,6 +13,7 @@
 #include <ctime>
 
 #include "layout_store.hpp"
+#include "waveform.hpp"
 
 namespace udpscope {
 namespace {
@@ -52,25 +53,30 @@ std::string stem_of(const std::string& file, const char* ext) {
 /// The palette is fixed rather than the plots': this is navigation, and what has to be told apart at
 /// a glance is one *event* from another, not one signal from another (for which the names are on the
 /// row above).
-bool write_preview(const ExportTable& table, const std::string& path, int width = 480, int height = 160) {
+///
+/// The height is **per strip**, not for the whole picture: with a fixed total, a six-signal event got
+/// 26 pixels a signal and an eight-signal one got 20, which is a smear and not a waveform -- the
+/// picture has to grow with the signal count, and it is the *viewer* that scales it down to a row.
+bool write_preview(const ExportTable& table, const std::string& path, int width = 480,
+                   int strip_h = 44) {
   if (table.empty() || table.columns.empty()) return false;
   const std::size_t rows = table.rows();
   const std::size_t strips = table.columns.size();
-  const int strip_h = std::max(6, height / static_cast<int>(strips));
   const int total_h = strip_h * static_cast<int>(strips);
   static const std::uint32_t kPalette[] = {0x4FA3FFu, 0xFF7A4Fu, 0x6EE07Au, 0xE06ED0u,
                                           0xFFD24Fu, 0x6FD8E0u, 0xB9A0FFu, 0xE0E0E0u};
 
-  // One byte per pixel per channel, bottom-up (BMP's own order), padded to a 4-byte row.
+  // One byte per pixel per channel, bottom-up and **blue first** -- both are BMP's own order, and
+  // writing RGB here is what made every external viewer show the traces in the wrong colour.
   const int row_bytes = ((width * 3) + 3) & ~3;
   std::vector<unsigned char> pixels(std::size_t(row_bytes) * total_h, 0);
   const auto put = [&](int x, int y, std::uint32_t rgb, double alpha) {
     if (x < 0 || y < 0 || x >= width || y >= total_h) return;
     unsigned char* p = &pixels[std::size_t(total_h - 1 - y) * row_bytes + std::size_t(x) * 3];
     const double a = std::clamp(alpha, 0.0, 1.0);
-    p[0] = static_cast<unsigned char>(p[0] * (1.0 - a) + ((rgb >> 16) & 0xFF) * a);
+    p[0] = static_cast<unsigned char>(p[0] * (1.0 - a) + (rgb & 0xFF) * a);
     p[1] = static_cast<unsigned char>(p[1] * (1.0 - a) + ((rgb >> 8) & 0xFF) * a);
-    p[2] = static_cast<unsigned char>(p[2] * (1.0 - a) + (rgb & 0xFF) * a);
+    p[2] = static_cast<unsigned char>(p[2] * (1.0 - a) + ((rgb >> 16) & 0xFF) * a);
   };
   // The background: a dark field, so the traces read the way they do on screen.
   for (int y = 0; y < total_h; ++y) {
@@ -268,6 +274,34 @@ std::string EventStore::save(const ExportTable& table, const EventRecord& meta,
   return samples;
 }
 
+std::string EventStore::redraw_preview(const EventRecord& record) const {
+  if (dir_.empty() || record.stem.empty() || record.file.empty()) return {};
+  WaveformReader reader;
+  std::string error;
+  if (!reader.open(record.file, &error)) return {};
+  // The whole event in one table, which an event can afford where an export cannot: it is bounded by
+  // the trigger's own pre/post window, so this is seconds of samples and not a session's worth.
+  ExportTable table;
+  table.columns.resize(reader.names().size());
+  for (std::size_t c = 0; c < table.columns.size(); ++c) {
+    table.columns[c].name = reader.names()[c];
+    table.columns[c].values.reserve(reader.rows());
+  }
+  table.time.reserve(reader.rows());
+  std::vector<float> values(reader.names().size(), 0.0f);
+  double t = 0.0;
+  double abs_t = 0.0;
+  while (reader.next(&t, &abs_t, values.data())) {
+    table.time.push_back(t);
+    for (std::size_t c = 0; c < table.columns.size(); ++c) {
+      table.columns[c].values.push_back(values[c]);
+    }
+  }
+  const std::string path = dir_ + "/" + record.stem + ".bmp";
+  if (!write_preview(table, path)) return {};
+  return path;
+}
+
 std::vector<EventRecord> EventStore::list() const {
   std::vector<EventRecord> out;
   if (dir_.empty()) return out;