monitor: watch for removal of non-native mounts on GVolumeMonitor

Fix https://github.com/mate-desktop/caja/issues/1066 "Caja caches folders from usb drives/disk"

Nowadays, we rely on G_FILE_MONITOR_EVENT_UNMOUNTED to be emitted when a
mount disappears, since we already monitor the directory, in order to
switch the view to a different location.
Since non-native mounts very likely won't have file monitoring though,
we're not going to receive such events in that case, and fail to
redirect the view as a consequence.
This patch fixes it by listening to the mount-removed signal on
GVolumeMonitor when a monitor is requested for a non-native mount, and
emulating a file removal in that case.

Backport  Nautilus commit gitlab.gnome.org/GNOME/nautilus/commit/3891241ba760c59d284b7579dbd340651c8d4d29

note that caja_get_mounted_mount_for_root had to be added, while the equivalent Nautilus function was from a prior commit

3 files changed, 96 insertions, 10 deletions

diff --git a/libcaja-private/caja-file-utilities.c b/libcaja-private/caja-file-utilities.c
index 237f85d7..46f90b0a 100644
--- a/libcaja-private/caja-file-utilities.c
+++ b/libcaja-private/caja-file-utilities.c
@@ -756,6 +756,48 @@ caja_is_desktop_directory (GFile *dir)
     return g_file_equal (dir, desktop_dir);
 }
 
+GMount *
+caja_get_mounted_mount_for_root (GFile *location)
+{
+	GVolumeMonitor *volume_monitor;
+	GList *mounts;
+	GList *l;
+	GMount *mount;
+	GMount *result = NULL;
+	GFile *root = NULL;
+	GFile *default_location = NULL;
+
+	volume_monitor = g_volume_monitor_get ();
+	mounts = g_volume_monitor_get_mounts (volume_monitor);
+
+	for (l = mounts; l != NULL; l = l->next) {
+		mount = l->data;
+
+		if (g_mount_is_shadowed (mount)) {
+			continue;
+		}
+
+		root = g_mount_get_root (mount);
+		if (g_file_equal (location, root)) {
+			result = g_object_ref (mount);
+			break;
+		}
+
+		default_location = g_mount_get_default_location (mount);
+		if (!g_file_equal (default_location, root) &&
+		    g_file_equal (location, default_location)) {
+			result = g_object_ref (mount);
+			break;
+		}
+	}
+
+	g_clear_object (&root);
+	g_clear_object (&default_location);
+	g_list_free_full (mounts, g_object_unref);
+
+	return result;
+}
+
 /**
  * caja_get_pixmap_directory
  *
diff --git a/libcaja-private/caja-file-utilities.h b/libcaja-private/caja-file-utilities.h
index 370cec02..2306601f 100644
--- a/libcaja-private/caja-file-utilities.h
+++ b/libcaja-private/caja-file-utilities.h
@@ -47,6 +47,7 @@ gboolean caja_is_desktop_directory               (GFile *dir);
 gboolean caja_is_home_directory                  (GFile *dir);
 gboolean caja_is_home_directory_file             (GFile *dir,
         const char *filename);
+GMount * caja_get_mounted_mount_for_root         (GFile *location);
 gboolean caja_is_in_system_dir                   (GFile *location);
 char *   caja_get_pixmap_directory               (void);
 
diff --git a/libcaja-private/caja-monitor.c b/libcaja-private/caja-monitor.c
index 0434dfe2..73d18f36 100644
--- a/libcaja-private/caja-monitor.c
+++ b/libcaja-private/caja-monitor.c
@@ -34,6 +34,9 @@
 struct CajaMonitor
 {
     GFileMonitor *monitor;
+    GVolumeMonitor *volume_monitor;
+    GMount *mount;
+    GFile *location;
 };
 
 gboolean
@@ -73,6 +76,27 @@ call_consume_changes_idle_cb (gpointer not_used)
 }
 
 static void
+schedule_call_consume_changes (void)
+{
+    if (call_consume_changes_idle_id == 0) {
+	    call_consume_changes_idle_id =
+        g_idle_add (call_consume_changes_idle_cb, NULL);
+	}
+}
+
+static void
+mount_removed (GVolumeMonitor *volume_monitor,
+               GMount *mount,
+               gpointer user_data)
+{
+    CajaMonitor *monitor = user_data;
+    if (mount == monitor->mount) {
+        caja_file_changes_queue_file_removed (monitor->location);
+        schedule_call_consume_changes ();
+    }
+}
+
+static void
 dir_changed (GFileMonitor* monitor,
              GFile *child,
              GFile *other_file,
@@ -115,12 +139,7 @@ dir_changed (GFileMonitor* monitor,
 
     g_free (uri);
     g_free (to_uri);
-
-    if (call_consume_changes_idle_id == 0)
-    {
-        call_consume_changes_idle_id =
-            g_idle_add (call_consume_changes_idle_cb, NULL);
-    }
+    schedule_call_consume_changes ();
 }
 
 CajaMonitor *
@@ -129,16 +148,33 @@ caja_monitor_directory (GFile *location)
     GFileMonitor *dir_monitor;
     CajaMonitor *ret;
 
+    ret = g_new0 (CajaMonitor, 1);
     dir_monitor = g_file_monitor_directory (location, G_FILE_MONITOR_WATCH_MOUNTS, NULL, NULL);
 
-    ret = g_new0 (CajaMonitor, 1);
-    ret->monitor = dir_monitor;
+    if (dir_monitor != NULL) {
+        ret->monitor = dir_monitor;
+    }
 
-    if (ret->monitor)
-    {
+    else if (!g_file_is_native (location)) {
+        ret->mount = caja_get_mounted_mount_for_root (location);
+        ret->location = g_object_ref (location);
+        ret->volume_monitor = g_volume_monitor_get ();
+    }
+
+    if (ret->monitor != NULL) {
+        g_signal_connect (ret->monitor, "changed",
+                  G_CALLBACK (dir_changed), ret);
+    }
+
+    if (ret->monitor) {
         g_signal_connect (ret->monitor, "changed", (GCallback)dir_changed, ret);
     }
 
+    if (ret->volume_monitor != NULL) {
+        g_signal_connect (ret->volume_monitor, "mount-removed",
+                    G_CALLBACK (mount_removed), ret);
+    }
+
     /* We return a monitor even on failure, so we can avoid later trying again */
     return ret;
 }
@@ -153,5 +189,12 @@ caja_monitor_cancel (CajaMonitor *monitor)
         g_object_unref (monitor->monitor);
     }
 
+    if (monitor->volume_monitor != NULL) {
+        g_signal_handlers_disconnect_by_func (monitor->volume_monitor, mount_removed, monitor);
+        g_object_unref (monitor->volume_monitor);
+    }
+
+    g_clear_object (&monitor->location);
+    g_clear_object (&monitor->mount);
     g_free (monitor);
 }