From f95fadd25e1c7689dfee76d56abc678c9d4a29d3 Mon Sep 17 00:00:00 2001
From: Bastien Bouclet <bastien.bouclet@gmail.com>
Date: Sun, 20 Jan 2019 17:50:43 +0100
Subject: [PATCH] STARK: Load replacement files from the mods directory

Each mod should be its own directory in the mods subdirectory
of the game data path. Mods are loaded in alphabetical order.
---
 README.md               | 25 +++++++++++++++++++++++++
 engines/stark/stark.cpp | 22 ++++++++++++++++++++++
 engines/stark/stark.h   |  1 +
 3 files changed, 48 insertions(+)

diff --git a/README.md b/README.md
index 64be69667c8..e9f849275b8 100644
--- a/README.md
+++ b/README.md
@@ -448,6 +448,31 @@ Command               | Description
 `location`            | Display the current location
 `testDecompiler`      | Test decompilation of all the scripts in game
 
+### 8.5. Modding The Longest Journey ###
+
+ResidualVM can load replacement assets instead of the original files for
+some of the asset types. By leveraging this capability, users can create
+mods for the game. These are the currently supported modding features:
+
+  * Load mods from the `mods` directory inside the game data path.
+  Each mod should be its own directory in the `mods` subdirectory.
+  Mods are loaded in alphabetical order.
+
+  * Load external PNG files instead of the XMG files inside the game
+  archives.
+    The replacement PNG files can have larger dimensions when compared to
+  the original XMG images, enabling the creation of a high resolution mod.
+    The game looks for the replacement files in a mod directory and then
+  in the `xarc` subdirectory of the directory containing the archive in
+  which the XMG picture to be replaced is located. For instance:
+  `mods/[my_mod]/1e/00/xarc/fountain_layercenter.png` needs to be used for
+  the Venice park background.
+    ResidualVM expects PNGs to be in pre-multiplied alpha format for improved
+  load times. However the `replacement_png_premultiply_alpha` `residualvm.ini`
+  setting allows to load regular transparency PNGs when set to `true` for
+  convenience when testing.
+
+Contact us if you need further capabilities for your mod.
 
 ## 9. Bug reports
 ResidualVM still has a few bugs, many might already have been reported,
diff --git a/engines/stark/stark.cpp b/engines/stark/stark.cpp
index c6e139964be..a17d26385c8 100644
--- a/engines/stark/stark.cpp
+++ b/engines/stark/stark.cpp
@@ -48,6 +48,7 @@
 #include "common/config-manager.h"
 #include "common/debug-channels.h"
 #include "common/events.h"
+#include "common/fs.h"
 #include "common/random.h"
 #include "common/savefile.h"
 #include "common/system.h"
@@ -67,6 +68,8 @@ StarkEngine::StarkEngine(OSystem *syst, const ADGameDescription *gameDesc) :
 	DebugMan.addDebugChannel(kDebugXRC, "XRC", "Debug the loading of XRC resource trees");
 	DebugMan.addDebugChannel(kDebugModding, "Modding", "Debug the loading of modded assets");
 	DebugMan.addDebugChannel(kDebugUnknown, "Unknown", "Debug unknown values on the data");
+
+	addModsToSearchPath();
 }
 
 StarkEngine::~StarkEngine() {
@@ -259,6 +262,25 @@ void StarkEngine::updateDisplayScene() {
 	StarkUserInterface->render();
 }
 
+static bool modsCompare(const Common::FSNode &a, const Common::FSNode &b) {
+	return a.getName() < b.getName();
+}
+
+void StarkEngine::addModsToSearchPath() const {
+	const Common::FSNode gameDataDir(ConfMan.get("path"));
+	const Common::FSNode modsDir = gameDataDir.getChild("mods");
+	if (modsDir.exists()) {
+		Common::FSList list;
+		modsDir.getChildren(list);
+
+		Common::sort(list.begin(), list.end(), modsCompare);
+
+		for (uint i = 0; i < list.size(); i++) {
+			SearchMan.addDirectory("mod_" + list[i].getName(), list[i], 0, 4);
+		}
+	}
+}
+
 bool StarkEngine::hasFeature(EngineFeature f) const {
 	return
 		(f == kSupportsLoadingDuringRuntime) ||
diff --git a/engines/stark/stark.h b/engines/stark/stark.h
index 9c51f6512f1..da57aac12d6 100644
--- a/engines/stark/stark.h
+++ b/engines/stark/stark.h
@@ -79,6 +79,7 @@ private:
 	void updateDisplayScene();
 	void processEvents();
 	void onScreenChanged() const;
+	void addModsToSearchPath() const;
 
 	Gfx::FrameLimiter *_frameLimiter;
 	Console *_console;