From 6879729633192eda246630e5770d7f5e49f7c869 Mon Sep 17 00:00:00 2001
From: Jonas Herzig <me@johni0702.de>
Date: Sun, 15 Nov 2020 13:17:00 +0100
Subject: [PATCH] Fix OpenEXR export option throwing UnsatisfiedLinkError on
 Windows

---
 ...in_WindowsWorkaroundForTinyEXRNatives.java | 81 +++++++++++++++++++
 .../resources/mixins.render.replaymod.json    |  1 +
 2 files changed, 82 insertions(+)
 create mode 100644 src/main/java/com/replaymod/render/mixin/Mixin_WindowsWorkaroundForTinyEXRNatives.java

diff --git a/src/main/java/com/replaymod/render/mixin/Mixin_WindowsWorkaroundForTinyEXRNatives.java b/src/main/java/com/replaymod/render/mixin/Mixin_WindowsWorkaroundForTinyEXRNatives.java
new file mode 100644
index 00000000..3df81c08
--- /dev/null
+++ b/src/main/java/com/replaymod/render/mixin/Mixin_WindowsWorkaroundForTinyEXRNatives.java
@@ -0,0 +1,81 @@
+//#if MC>=11400
+package com.replaymod.render.mixin;
+
+import org.lwjgl.system.Library;
+import org.lwjgl.system.Platform;
+import org.lwjgl.util.tinyexr.TinyEXR;
+import org.spongepowered.asm.mixin.Mixin;
+import org.spongepowered.asm.mixin.injection.At;
+import org.spongepowered.asm.mixin.injection.ModifyArg;
+
+import java.io.File;
+import java.io.IOException;
+import java.io.InputStream;
+import java.net.URL;
+import java.nio.file.Files;
+import java.nio.file.Path;
+import java.nio.file.Paths;
+import java.nio.file.StandardCopyOption;
+import java.util.function.Consumer;
+import java.util.regex.Pattern;
+
+/**
+ * It appears like natives on Windows cannot be loaded if one of their dependencies has already been loaded by a
+ * different class loader. In our case we cannot load tinyexr (on the knot class loader) because lwjgl has already
+ * been loaded on the system class loader.
+ *
+ * If we force the tinyexr native to load on the system class loader (by calling `Library.loadSystem(absPath)`),
+ * it'll load but we'll get an error when we call any of the native methods.
+ *
+ * We can't really load TinyEXR itself via the system class loader because Java does not provide any methods for
+ * modifying the system class path at runtime and we'd have to use JVM-specific hacks.
+ *
+ * Strangely, if we use System.loadLibrary instead of System.load, then it all just works. This mixin implements
+ * that workaround by finding MC's natives folder, extracting the dll from our jar into that folder and then replacing
+ * the context class passed to Library.loadSystem (which it uses to find dlls in jars) with Library (which is on the
+ * system class loader) so it cannot find the dll in our jar and falls back to using System.loadLibrary.
+ */
+@Mixin(value = TinyEXR.class, remap = false)
+public class Mixin_WindowsWorkaroundForTinyEXRNatives {
+    private static final String LOAD_SYSTEM_CONSUMERS = "Lorg/lwjgl/system/Library;loadSystem(Ljava/util/function/Consumer;Ljava/util/function/Consumer;Ljava/lang/Class;Ljava/lang/String;)V";
+
+    @ModifyArg(method = "<clinit>", at = @At(value = "INVOKE", target = LOAD_SYSTEM_CONSUMERS))
+    private static Class<?> uglyWindowsHacks(Consumer<String> load, Consumer<String> loadLibrary, Class<?> context, String name) throws IOException {
+        if (Platform.get() != Platform.WINDOWS) {
+            return context; // works out of the box on linux
+        }
+
+        name = System.mapLibraryName(name);
+
+        URL libURL = context.getClassLoader().getResource(name);
+        if (libURL == null) {
+            throw new UnsatisfiedLinkError("Failed to locate library: " + name);
+        }
+
+        String lwjglLibName = Library.JNI_LIBRARY_NAME;
+        if (!lwjglLibName.endsWith(".dll")) {
+            lwjglLibName = System.mapLibraryName(lwjglLibName);
+        }
+
+        String paths = System.getProperty("java.library.path");
+        Path nativesDir = null;
+        for (String dir : Pattern.compile(File.pathSeparator).split(paths)) {
+            Path path = Paths.get(dir);
+            if (Files.isReadable(path.resolve(lwjglLibName))) {
+                nativesDir = path;
+                break;
+            }
+        }
+        if (nativesDir == null) {
+            throw new UnsatisfiedLinkError("Failed to locate natives folder in " + paths);
+        }
+
+        Path libPath = nativesDir.resolve(name);
+        try (InputStream source = libURL.openStream()) {
+            Files.copy(source, libPath, StandardCopyOption.REPLACE_EXISTING);
+        }
+
+        return Library.class;
+    }
+}
+//#endif
diff --git a/src/main/resources/mixins.render.replaymod.json b/src/main/resources/mixins.render.replaymod.json
index 9a7ca987..976fbf9b 100644
--- a/src/main/resources/mixins.render.replaymod.json
+++ b/src/main/resources/mixins.render.replaymod.json
@@ -19,6 +19,7 @@
     //#endif
     //#if MC>=11400
     "Mixin_PreserveDepthDuringHandRendering",
+    "Mixin_WindowsWorkaroundForTinyEXRNatives",
     "MainWindowAccessor",
     //#endif
     "WorldRendererAccessor",