mythfrontend/galleryviews.cpp: replace floating point random numbers

with fixed point

Generating uniformly random floating point values is difficult and
most implementations are currently bugged and may return the upper
bound when they are supposed to be half open intervals.

Instead, scale the `double`s to `uint32_t`s and use uniformly random
integers.

mythtv/programs/mythfrontend/galleryviews.cpp

@@ -2,8 +2,10 @@
 
 #include <algorithm> // std::shuffle, upper_bound
 #include <cmath>     // std::pow
+#include <cstdint>
 #include <iterator>  // std::distance
 #include <random>
+#include <vector>
 
 #include "libmythbase/mythrandom.h"
 
@@ -270,18 +272,21 @@ void FlatView::Populate(ImageList &files)
         }
         else if (m_order == kSeasonal)
         {
-            WeightList weights   = CalculateSeasonalWeights(files);
-            double     maxWeight = weights.last();
-
-            static std::random_device rd;
-            static auto generator = MythRandomGenerator_32(rd());
-            auto distrib = std::uniform_real_distribution(0.0, maxWeight);
-            // TODO use fixed not floating point
+            WeightList cdf = CalculateSeasonalWeights(files); // not normalized to 1.0
+            std::vector<uint32_t> weights;
+            weights.reserve(cdf.size());
+            for (int i = 0; i < cdf.size(); i++)
+            {
+                weights.emplace_back(lround(cdf[i] / cdf.back() * UINT32_MAX));
+            }
+            // exclude the last value so the past the end iterator is not returned
+            // by std::upper_bound
+            uint32_t maxWeight = weights.back() - 1;
 
             for (int count = 0; count < files.size(); ++count)
             {
-                double randWeight = distrib(generator);
-                WeightList::iterator it =
+                uint32_t randWeight = MythRandom(0, maxWeight);
+                std::vector<uint32_t>::iterator it =
                         std::upper_bound(weights.begin(), weights.end(), randWeight);
                 int    index      = std::distance(weights.begin(), it);
                 m_sequence.append(files.at(index)->m_id);