Export runtime detected paths to lua scripts. Adapt stopwatch to not use
hardcoded path.

Change-Id: I5b843002d63a332b3fad02973d00b9863d283062
diff --git a/apps/plugins/lua/rocklib.c b/apps/plugins/lua/rocklib.c
index 809b269..6a6be38 100644
--- a/apps/plugins/lua/rocklib.c
+++ b/apps/plugins/lua/rocklib.c
@@ -699,7 +699,8 @@
 extern const luaL_Reg rocklib_aux[];
 
 
-#define RB_CONSTANT(x) lua_pushinteger(L, x); lua_setfield(L, -2, #x);
+#define RB_CONSTANT(x)        lua_pushinteger(L, x); lua_setfield(L, -2, #x);
+#define RB_STRING_CONSTANT(x) lua_pushstring(L, x); lua_setfield(L, -2, #x);
 /*
  ** Open Rockbox library
  */
@@ -727,6 +728,15 @@
     RB_CONSTANT(SCREEN_REMOTE);
 #endif
 
+    /* some useful paths constants */
+    RB_STRING_CONSTANT(ROCKBOX_DIR);
+    RB_STRING_CONSTANT(HOME_DIR);
+    RB_STRING_CONSTANT(PLUGIN_DIR);
+    RB_STRING_CONSTANT(PLUGIN_APPS_DATA_DIR);
+    RB_STRING_CONSTANT(PLUGIN_GAMES_DATA_DIR);
+    RB_STRING_CONSTANT(PLUGIN_DATA_DIR);
+    RB_STRING_CONSTANT(VIEWERS_DATA_DIR);
+
     rli_init(L);
 
     return 1;
diff --git a/apps/plugins/stopwatch.lua b/apps/plugins/stopwatch.lua
index c8fac3c..87773e3 100644
--- a/apps/plugins/stopwatch.lua
+++ b/apps/plugins/stopwatch.lua
@@ -25,7 +25,7 @@
 require "actions"
 require "buttons"
 
-STOPWATCH_FILE = "/.rockbox/rocks/apps/stopwatch.dat"
+STOPWATCH_FILE = rb.PLUGIN_APPS_DATA_DIR .. "/stopwatch.dat"
 
 
 local LapsView = {