[KevinH]

Actually no. When you close a tab, that tab is scheduled to be deleted later (memory freed) under control of its parent. So Qt determines when that tab's memory will be deleted and thereby freed. Please note, there is a huge differences between memory used and memory leaked.

For an app of close to 150 meg in uncompressed size to consume 370 meg of virtual memory is nothing unusual. So you are not seeing a "leak", you are seeing Qt trying to optimize performance by using memory to hold caches and things to speed things up. This does not make for a smallest memory footprint.

Again, many images, icons and things are loaded into caches which will not be cleared until some image or icon resource is no longer needed. Looking at process total memory can be very misleading in many ways because of mmaping and memory caches.

My worry was that if left idle that Sigil would continue to leak memory but that does not appear to be the case given earlier responses.

I know the valgrind tool exists to look for memory leaks and macOS has a "leaks command-line tool". I have run the macOS leaks tool and almost every minor leak is associated with Pixmaps or icons set up once per MainWindow (in Mac with Sigil you have one app with multiple main windows, unlike the other platforms). There are also different objects that are pointers to mac native widgets used behind the scene.

So far, at least on mac, things appear to be reasonably stable in memory. If anyone has access to valgrind and could use it to check under Linux that would be usefull.

I am not sure if valgrind can be used under Windows.