Support opening collections of files

Implement a process-local VFS to enable grouping together arbitrary
URIs passed via program arguments, DnD, or the file open dialog.

This VFS contains FivCollectionFile objects, which act as "simple"
proxies over arbitrary GFiles.  Their true URIs may be retrieved
through the "standard::target-uri" attribute, in a similar way to
GVfs's "recent" and "trash" backends.

(The main reason we proxy rather than just hackishly return foreign
GFiles from the VFS is that loading them would switch the current
directory, and break iteration as a result.

We could also keep the collection outside of GVfs, but that would
result in considerable special-casing, and the author wouldn't gain
intimate knowledge of GIO.)

There is no perceived need to keep old collections when opening
new ones, so we simply change and reload the contents when needed.

Similarly, there is no intention to make the VFS writeable.

The process-locality of this and other URI schemes has proven to be
rather annoying when passing files to other applications,
however most of the resulting complexity appears to be essential
rather than accidental.

Note that the GTK+ file chooser widget is retarded, and doesn't
recognize URIs that lack the authority part in the location bar.

1 files changed, 25 insertions, 0 deletions

diff --git a/fiv-collection.h b/fiv-collection.h
new file mode 100644
index 0000000..62dd336
--- /dev/null
+++ b/fiv-collection.h
@@ -0,0 +1,25 @@
+//
+// fiv-collection.h: GVfs extension for grouping arbitrary files together
+//
+// Copyright (c) 2022, Přemysl Eric Janouch <p@janouch.name>
+//
+// Permission to use, copy, modify, and/or distribute this software for any
+// purpose with or without fee is hereby granted.
+//
+// THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
+// WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
+// MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY
+// SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
+// WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION
+// OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF OR IN
+// CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
+//
+
+#include <gio/gio.h>
+
+#define FIV_COLLECTION_SCHEME "collection"
+
+gboolean fiv_collection_uri_matches(const char *uri);
+GFile **fiv_collection_get_contents(gsize *len);
+void fiv_collection_reload(gchar **uris);
+void fiv_collection_register(void);