Use /twres instead of /res for theme resources

AOSP and other ROM trees now do a rm -rf of the res folder during
the ramdisk creation process that removes the TWRP resources.
Using /twres instead of /res works around this issue making TWRP
more compatible with AOSP and other build trees.

Change-Id: I0d4c7e06ca381ac5aa0069b6f2b8c47f7dec49e7
diff --git a/gui/gui.cpp b/gui/gui.cpp
index 9b918f0..fecc032 100644
--- a/gui/gui.cpp
+++ b/gui/gui.cpp
@@ -715,11 +715,12 @@
 extern "C" int gui_init(void)
 {
 	gr_init();
+	std::string curtain_path = TWRES "images/curtain.jpg";
 
-	if (res_create_surface("/res/images/curtain.jpg", &gCurtain))
+	if (res_create_surface(curtain_path.c_str(), &gCurtain))
 	{
 		printf
-		("Unable to locate '/res/images/curtain.jpg'\nDid you set a DEVICE_RESOLUTION in your config files?\n");
+		("Unable to locate '%s'\nDid you set a DEVICE_RESOLUTION in your config files?\n", curtain_path.c_str());
 		return -1;
 	}
 
@@ -734,9 +735,10 @@
 #ifndef TW_OEM_BUILD
 	int check = 0;
 	DataManager::GetValue(TW_IS_ENCRYPTED, check);
+
 	if (check)
 	{
-		if (PageManager::LoadPackage("TWRP", "/res/ui.xml", "decrypt"))
+		if (PageManager::LoadPackage("TWRP", TWRES "ui.xml", "decrypt"))
 		{
 			LOGERR("Failed to load base packages.\n");
 			goto error;
@@ -771,7 +773,7 @@
 		if (check || PageManager::LoadPackage("TWRP", theme_path, "main"))
 		{
 #endif // ifndef TW_OEM_BUILD
-			if (PageManager::LoadPackage("TWRP", "/res/ui.xml", "main"))
+			if (PageManager::LoadPackage("TWRP", TWRES "ui.xml", "main"))
 			{
 				LOGERR("Failed to load base packages.\n");
 				goto error;
@@ -807,7 +809,7 @@
 		// There is a custom theme, try to load it
 		if (PageManager::ReloadPackage("TWRP", theme_path)) {
 			// Custom theme failed to load, try to load stock theme
-			if (PageManager::ReloadPackage("TWRP", "/res/ui.xml")) {
+			if (PageManager::ReloadPackage("TWRP", TWRES "ui.xml")) {
 				LOGERR("Failed to load base packages.\n");
 				goto error;
 			}