Fix some Elements thumbnail bugs

Author: ddennedy

src/models/elementsmodel.cpp

@@ -77,7 +77,7 @@ class ElementsThumbnailTask : public QRunnable
                 producer.attach(converter);
                 const auto width = PlaylistModel::THUMBNAIL_WIDTH * 2;
                 const auto height = PlaylistModel::THUMBNAIL_HEIGHT * 2;
-                image = MLT.image(producer, 0, width, height);
+                image = MLT.image(producer, producer.get_length() / 2, width, height);
             }
         }
         if (!image.isNull()) {
@@ -162,6 +162,14 @@ int ElementsModel::rowCount(const QModelIndex &parent) const
     return m_files.count();
 }
 
+static void cacheThumbnail(ElementsModel *model,
+                           const QString &filePath,
+                           QImage &image,
+                           const QModelIndex &index)
+{
+    model->updateThumbnail(filePath, image, index);
+}
+
 QVariant ElementsModel::data(const QModelIndex &index, int role) const
 {
     if (!index.isValid() || index.row() >= m_files.count())
@@ -188,6 +196,7 @@ QVariant ElementsModel::data(const QModelIndex &index, int role) const
         const auto key = ElementsThumbnailTask::cacheKey(info.filePath());
         auto image = DB.getThumbnail(key);
         if (image.isNull()) {
+            ::cacheThumbnail(const_cast<ElementsModel *>(this), info.filePath(), image, index);
             QThreadPool::globalInstance()->start(
                 new ElementsThumbnailTask(const_cast<ElementsModel *>(this),
                                           info.filePath(),
@@ -236,12 +245,16 @@ void ElementsModel::setDir(const QDir &dir)
     endResetModel();
 }
 
-void ElementsModel::updateThumbnail(const QString &filePath,
-                                    QImage &image,
-                                    const QModelIndex &persistentIndex)
+void ElementsModel::updateThumbnail(const QString &filePath, QImage &image, const QModelIndex &index)
 {
-    const auto key = ElementsThumbnailTask::cacheKey(filePath);
+    bool updateModel = !image.isNull();
+
+    if (image.isNull()) {
+        image = QImage(64, 64, QImage::Format_ARGB32);
+        image.fill(Qt::transparent);
+    }
+    auto key = ElementsThumbnailTask::cacheKey(filePath);
     DB.putThumbnail(key, image);
-    if (persistentIndex.isValid())
-        emit dataChanged(persistentIndex, persistentIndex, {ThumbnailRole});
+    if (updateModel)
+        emit dataChanged(index, index);
 }