view filter fix-up: randomized slideshow

Author: luebking

Phototonic.cpp

@@ -2719,10 +2719,22 @@ void Phototonic::slideShowHandler() {
         thumbsViewer->setCurrentIndex(next);
     last = thumbsViewer->currentIndex().row();
 
-    if (Settings::slideShowRandom)
-        next = QRandomGenerator::global()->bounded(thumbsViewer->model()->rowCount());
-    else
+    if (Settings::slideShowRandom) {
+        next = QRandomGenerator::global()->bounded(thumbsViewer->visibleThumbs());
+        if (thumbsViewer->visibleThumbs() != thumbsViewer->model()->rowCount()) {
+            // for the filtered case we've to figure the nth non-hidden thumb, naively picking some
+            // number and moving to the next visible will cause less than random results if a huge
+            // block is hidden because we'll often end at its adjacent indexes
+            int n = next;
+            for (next = 0; next < thumbsViewer->model()->rowCount(); ++next) {
+                if (!thumbsViewer->isRowHidden(next) && --n < 0)
+                    break;
+            }
+        }
+            
+    } else {
         next = thumbsViewer->nextRow();
+    }
 
     if (next < 0)
         next = Settings::wrapImageList ? 0 : -2;

ThumbsViewer.cpp

@@ -442,6 +442,7 @@ void ThumbsViewer::reLoad() {
     histFiles.clear(); // these can grow out of control and currently sort O(n^2)
     histograms.clear();
     m_histSorted = false;
+    m_visibleThumbs = 0;
 
     loadPrepare();
 
@@ -711,6 +712,8 @@ void ThumbsViewer::filterRows(int first, int last) {
         setRowHidden(i, false);
     }
 
+    m_visibleThumbs += shown.size() - hidden.size();
+
     if (!hidden.isEmpty())
         emit filesHidden(hidden);
     if (!shown.isEmpty())

ThumbsViewer.h

@@ -140,6 +140,7 @@ Q_OBJECT
     bool isBusy() { return m_busy; }
     static int removeFromCache(const QString &path);
     static int moveCache(const QString &oldpath, const QString &newpath);
+    int visibleThumbs() const { return m_visibleThumbs; }
     QDir thumbsDir;
     QDir::SortFlags thumbsSortFlags;
     int thumbSize;
@@ -201,6 +202,7 @@ Q_OBJECT
     QStandardItemModel *m_model;
     QString m_desiredThumbPath;
     bool m_filterDirty;
+    int m_visibleThumbs;
 
 public slots:
     void invertSelection();