0009-Add-stateless-path-for-mimeinfo.cache.patch

From ae1fb9eb49c8730cd270095a85ad5b164ee788bc Mon Sep 17 00:00:00 2001
From: "Brett T. Warden" <brett.t.warden@intel.com>
Date: Thu, 15 Aug 2024 14:24:49 -0700
Subject: [PATCH] Add stateless path for mimeinfo.cache

We previously modified update-desktop-database and mime-update.service to
generate mimeinfo.cache for /usr/share/applications under
/var/cache/applications. When gio attempts to read it as part of
scanning /usr/share/applications, redirect it to
/var/cache/applications instead.

Complicated explanation:
gio expects a mimeinfo.cache file in the same directory as the .desktop
files it indexes. It will scan each candidate directory's mimeinfo.cache
to find a match, but not the .desktop files themselves. After selecting
a .desktop file (whether it exists in that directory or not), it will
check other directories, by priority, to see if an equivalent .desktop
file exists there too. If so, it will *not* use the .desktop file in the
same directory as the matching mimeinfo.cache. At the same time, if no
mimeinfo.cache file exists in a given directory, it will never consider
the .desktop files in that directory as possible matches.

Example:
- /usr/share/applications/org.gnome.OnlineAccounts.Oauth2.desktop exists
- /var/cache/applications/org.gnome.OnlineAccounts.Oauth2.desktop *does not* exist
- /var/cache/applications/mimeinfo.cache maps a MIME type to org.gnome.OnlineAccounts.Oauth2.desktop.
- /usr/share/applications/mimeinfo.cache *does not* exist
- gio will not find a match in /usr/share/applications/mimeinfo.cache, since it does not exist
- gio will determine that /var/cache/applications/org.gnome.OnlineAccounts.Oauth2.desktop
  is a possible match, but it will also determine that
  /usr/share/applications/org.gnome.OnlineAccounts.Oauth2.desktop has
  higher priority, so will mask the /var/cache/applications match.
- gio will have no match to offer.

Fix:
When gio tries to read mimeinfo.cache in /usr/share/applications, make
it open /var/cache/applications/mimeinfo.cache instead. This will
provide gio with the correct mapping for the .desktop files in
/usr/share/applications.

Caveat:
gio will read /var/cache/application/mimeinfo.cache again while
attempting to scan /var/cache/applications, but since no .desktop files
will exist there, this shouldn't cause a problem.

Long-term: glib/GNOME should be taught to use lookaside paths for cached
data.
---
 gio/gdesktopappinfo.c | 11 ++++++++++-
 1 file changed, 10 insertions(+), 1 deletion(-)

diff --git a/gio/gdesktopappinfo.c b/gio/gdesktopappinfo.c
index 87db7a97a1eb..0ebfaf07aa8a 100644
--- a/gio/gdesktopappinfo.c
+++ b/gio/gdesktopappinfo.c
@@ -1023,7 +1023,16 @@ desktop_file_dir_unindexed_read_mimeapps_lists (DesktopFileDir *dir)
   /* Finally, the mimeinfo.cache, which is just a cached copy of what we
    * would find in the MimeTypes= lines of all of the desktop files.
    */
-  filename = g_strdup_printf ("%s/mimeinfo.cache", dir->path);
+  if (0 == strcmp("/usr/share/applications", dir->path)) {
+    // For Clear Linux, we keep mimeinfo.cache for /usr/share/applications in
+    // /var/cache/applications/mimeinfo.cache. Corresponding patch in
+    // desktop-file-utils adds an option to /usr/bin/update-desktop-database to
+    // output the cache file in /var/cache/applications.
+    filename = g_strdup_printf ("/var/cache/applications/mimeinfo.cache");
+  }
+  else {
+    filename = g_strdup_printf ("%s/mimeinfo.cache", dir->path);
+  }
   desktop_file_dir_unindexed_read_mimeapps_list (dir, filename, MIME_CACHE_GROUP, TRUE);
   g_free (filename);
 }
-- 
2.46.0