Before this commit folder with no direct comics (only subfolders) didn't have a cover image to be displayed. Now updating the children info is done recursively and subfolders are taken into account.
This affects the iOS client remote browser so far, but it is also needed for the future browser update (display folders as a grid instead of using EmptyFolderWidget)
Otherwise we can end with huge cover files if the source content has abnormally tall covers. This large files could end exhausting RAM in the iOS client.
Creating a folder in search mode selects it and makes the UI look
half-way between Normal and Searching navigation statuses.
An alternative fix is to disable addFolderAction in search mode. But
this is more difficult to implement and inconsistent with the other
always-enabled folder and reading list actions.
ConcurrentQueue is currently used only by two classes and a test, but
modifying concurrent_queue.h requires recompiling 30 source files. None
of the member functions is so lightweight as to make it worth inlining.
An alternative to `@note ConcurrentQueue is unable to execute jobs if
@p threadCount == 0.` is `assert(threadCount != 0);`. But this would
force classes that contain a ConcurrentQueue data member to always start
a thread, even if they detect at runtime that they are never going to
enqueue a job.
Add Job type alias to avoid repeating the type.
Use default member initializers instead of the member initializer list
to make it clear [to the reader of the header] that no data member is
left uninitialized.
