plugins: Disk Tidy: wait for dircache

Running Disk Tidy while the dircache is loading is a lot
slower than waiting for it to finish building first.

Typical scenarios for this would be starting Disk Tidy
immediately after booting or after unplugging from USB.

Deleting files during a dircache build also seems to easily
result in memory corruption, as evidenced by visual glitches
appearing in the theme.

Change-Id: I9250d918d916b112ffe2504a9225a0b52bcc3622

apps/plugin.c

@@ -871,6 +871,9 @@ static const struct plugin_api rockbox_api = {
 #endif
     strstr,
     sb_set_title_text,
+#ifdef HAVE_DIRCACHE
+    dircache_wait,
+#endif
 };
 
 static int plugin_buffer_handle;

apps/plugin.h

@@ -1022,6 +1022,9 @@ struct plugin_api {
 #endif
     char* (*strstr)(const char *s1, const char *s2);
     bool (*sb_set_title_text)(const char* title, enum themable_icons icon, enum screen_type screen);
+#ifdef HAVE_DIRCACHE
+    void (*dircache_wait)(void);
+#endif
 };
 
 /* plugin header */

apps/plugins/disktidy.c

@@ -734,6 +734,10 @@ static enum plugin_status tidy_lcd_menu(void)
         switch(rb->do_menu(&menu, &selection, NULL, false)) {
             case 0:
                 if (tidy_types_selected()) {
+#ifdef HAVE_DIRCACHE
+                    rb->splash(0, ID2P(LANG_WAIT));
+                    rb->dircache_wait();
+#endif
                     disktidy_status = tidy_do();
                     if (disktidy_status == PLUGIN_OK)
                         disktidy_status = display_run_stats();