Prevent generating previews all the time during downloading a large file

When downloading a large file the preview should not be recreated each time
a change-notification has been received. Create the preview after getting
the first file change, but postpone creating the next previews until no change
has been done during a longer period of time.

BUG: 290698
FIXED-IN: 4.8.0

1 files changed, 15 insertions, 0 deletions

diff --git a/src/kitemviews/kfileitemmodelrolesupdater.h b/src/kitemviews/kfileitemmodelrolesupdater.h
index b7d8ceab0..5ed45a6ec 100644
--- a/src/kitemviews/kfileitemmodelrolesupdater.h
+++ b/src/kitemviews/kfileitemmodelrolesupdater.h
@@ -126,6 +126,13 @@ private slots:
     void resolvePendingRoles();
     void resolveNextPendingRoles();
 
+    /**
+     * Resolves items that have not been resolved yet after the change has been
+     * notified by slotItemsChanged(). Is invoked if the m_changedItemsTimer
+     * exceeds.
+     */
+    void resolveChangedItems();
+
 private:
     /**
      * Updates the roles for the given item ranges. The roles for the currently
@@ -189,6 +196,14 @@ private:
     QList<KJob*> m_previewJobs;
 
     QTimer* m_resolvePendingRolesTimer;
+
+    // When downloading or copying large files, the slot slotItemsChanged()
+    // will be called periodically within a quite short delay. To prevent
+    // a high CPU-load by generating e.g. previews for each notification, the update
+    // will be postponed until no file change has been done within a longer period
+    // of time.
+    QTimer* m_changedItemsTimer;
+    QSet<KFileItem> m_changedItems;
 };
 
 #endif