All options are now applied without restarting

Instances manager: cleanup, now explicitly state the error message
Moved init_loadCustomEnv() back to JavaLauncher.m

Natives/JavaLauncher.m

@@ -46,6 +46,43 @@ NSString *renderer_pre;
 NSString *allocmem_pre;
 NSString *multidir_pre;
 
+void init_loadCustomEnv() {
+    /* Define default env */
+
+    // I accidentally patched a bit wrong, the value should be a path containing libawt_xawt.dylib, but here is libawt.dylib path (no need to exist)
+    setenv("JAVA_AWT_PATH", [NSString stringWithFormat:@"%s/Frameworks/libawt.dylib", getenv("BUNDLE_PATH")].UTF8String, 1);
+
+    // Disable overloaded functions hack for Minecraft 1.17+
+    setenv("LIBGL_NOINTOVLHACK", "1", 1);
+
+    // Override OpenGL version to 4.1 for Zink
+    setenv("MESA_GL_VERSION_OVERRIDE", "4.1", 1);
+
+    /* Load custom env */
+    FILE *envFile = fopen([NSString stringWithFormat:@"%s/custom_env.txt", getenv("POJAV_HOME")].UTF8String, "r");
+
+    regLog("[Pre-init] Reading custom environment variables (custom_env.txt), opened=%d\n", envFile != NULL);
+
+    if (envFile) {
+        char *line = NULL;
+        size_t len = 0;
+        ssize_t read;
+        while ((read = getline(&line, &len, envFile)) != -1) {
+            if (line[0] == '#' || line[0] == '\n') continue;
+            if (line[read-1] == '\n') {
+                line[read-1] = '\0';
+            }
+            if (strchr(line, '=') != NULL) {
+                regLog("[Pre-init] Added custom env: %s", line);
+                setenv(strtok(line, "="), strtok(NULL, "="), 1);
+            } else {
+                regLog("[Pre-init] Warning: skipped empty value custom env: %s", line);
+            }
+        }
+        fclose(envFile);
+    }
+}
+
 void init_loadCustomJvmFlags() {
     NSString *jvmargs = getPreference(@"java_args");
     BOOL isFirstArg = YES;
@@ -94,6 +131,8 @@ NSString* environmentFailsafes(int minVersion) {
 int launchJVM(NSString *username, NSString *selectedVersion, int width, int height, int minVersion) {
     sprintf((char*) java_libs_path, "%s/libs", getenv("BUNDLE_PATH"));
 
+    init_loadCustomEnv();
+
     regLog("[JavaLauncher] Beginning JVM launch\n");
 
     NSString *javaHome_pre = getPreference(@"java_home");