...PM doesn't know anything about C1 Sessions.
Satisfying every possible C1 session folder arrangement may be impossible for PM. The C1 session user can pretty much scatter image files over their disks. C1 does however; come with a default template for a session folder arrangement. The user can design other session folder templates (it may be an somewhat underused feature of C1).
A session is pretty much defined by the existence of a little database file having the file name form <session_name>.cosessiondb as shown in the image in the thread opening post. The user opens an existing session in C1 by navigating to the .cosessiondb file (the session database).
The C1 default session template dictates that the session folder, the folder where the .cosessiondb file is located, has four image sub folders (Capture, Selects, Output and Trash). Depending on how the user arranges a particular session, those image folders may have sub folders. There may also be image folders outside the session folder hierarchy. In fact, there is no need to have images under the umbrella of the session folder at all. See Graham's posting and note his comment on "dummy session".
A single "dummy session" saves a little disk space because the user only needs one session, images can be in any folder structure outside that dummy session folder where the dummy.cosessiondb is located. Some C1 users are annoyed by the C1 session specific folders and files and want to see only one session folder instance which is the minimum set of C1 session files and folders that they can not avoid. Images can then be stored at will. The user opens the dummy session, points C1 to the next image folder to be included in the dummy session. C1 updates the dummy.cosessiondb accordingly. Personally, I do not use a dummy session.
A typical session along the lines of the C1 default session template, starts out with all source images in the Capture folder (or in sub folders). Source image files are potentially moved from Capture to the Selects folder or to the Trash folder. Image files created by C1, meaning exporting source images with C1 adjustments burned in, go to the Output folder (or sub folders), but it depends largely on how the user has set up recipes for export. I may use multiple recipes in parallel for additional export to folders outside the session.
I use C1 sessions, and PM is always my front end where I ingest and create a session-folder-to-be with one sub folder named Capture. That is part of my ingest setups, I pick one setup via the lightning bolt. My image files ingest directly to a folder inside the Capture folder. The session-folder-to-be is still not a C1 session, there is no .cosessiondb. C1 creates the .cosessiondb and the Selects, Output, Trash folders when I create a new session in C1 and feed it the name of the session-folder-to-be created by PM ingest if it did not exist.
If we stick to the C1 default session template, I can select the session folder in PM and have it open sub folders to see images in Capture, Selects, Output and Trash in one contact sheet. I rarely do that, but I may occasionally select the Capture folder and include its sub folders. There are normally no images in my Capture folder, I keep images in sub folders of Capture. I usually just point PM directly to a Capture image sub folder. BUT! This may vary greatly among C1 session users.
If PM is to "understand" C1 sessions in the general sense and open all session image thumbnails in a contact sheet, I believe PM must find them via the session database (the .cosessiondb file), looking at session folder and sub folder hierarchy will not do.
If PM is to show image thumbnails for C1 sessions strictly limited to the C1 default template (the session folder's image sub folders again), a potential solution would be a tick box for "always include images in all sub and sub sub... folders". A C1 session folder may have more sub folders than the four default folders (Capture, Selects, Output and Trash), but they would at least be in the session folder. PM could perhaps warn the user with a Yes/No dialog "The contact sheet needs to retrieve X tens of thousands thumbnails, are you sure?" X being a user preference image count.
A user preference setting "always include images in sub and sub sub... folders" could perhaps fit the needs of the thread opener and perhaps also Soizic, and it could be a general thing without PM knowing anything about C1 sessions.
A more elaborate solution could potentially let the PM user define a set (multiple sets?) of sibling folder names (say Capture, Selects) and the "always include images in sub and sub sub... folders" could use a defined set rather than "all" when opening a new contact sheet. Pointing PM to a session folder (more generally to any "root" folder) could then present thumbnails for images in the root folder and hierarchies in the predefined named sub folders (Capture, Selects,...). Again, that would not be a C1 specific feature, but more like a contact showing images in a clicked root folder and sub folders according to a fixed folder naming scheme. Potentially useful outside C1.
I hope the thread opener OldRadioGuy, Soizic and other C1 users can join forces to elaborate a bit on what functionality could be implemented in PM to make it somewhat more C1-friendly without breaking the PM concept and not requiring very C1 specific features.
