feat(ui): JVM arguments setting

packages/oneclient_app/src/view/app/cluster/cluster_settings.rs

@@ -79,6 +79,7 @@ impl Component for ClusterSettings {
                         }
                         .into_element(),
                     )
+                    .child(text_row(cluster_id, TextField::JvmArgs, &profile, &global))
                     .child(section_header("GAME"))
                     .child(
                         ToggleRow {
@@ -420,6 +421,7 @@ impl Component for ResolutionRow {
 
 #[derive(Clone, Copy, PartialEq)]
 enum TextField {
+    JvmArgs,
     Pre,
     Wrapper,
     Post,
@@ -428,6 +430,12 @@ enum TextField {
 impl TextField {
     fn meta(self) -> (IconType, &'static str, &'static str, &'static str) {
         match self {
+            Self::JvmArgs => (
+                IconType::Terminal,
+                "JVM Arguments",
+                "Extra arguments passed to Java. Separate them with spaces; quote values containing spaces.",
+                "-XX:+UseG1GC",
+            ),
             Self::Pre => (
                 IconType::FilePlus02,
                 "Pre-Launch Command",
@@ -451,6 +459,7 @@ impl TextField {
 
     fn value(self, profile: &GameSettingsProfile) -> Option<String> {
         match self {
+            Self::JvmArgs => profile.launch_args.clone(),
             Self::Pre => profile.hook_pre.clone(),
             Self::Wrapper => profile.hook_wrapper.clone(),
             Self::Post => profile.hook_post.clone(),
@@ -460,6 +469,7 @@ impl TextField {
     fn patch(self, value: Patch<String>) -> ProfileUpdate {
         let mut u = ProfileUpdate::default();
         match self {
+            Self::JvmArgs => u.launch_args = value,
             Self::Pre => u.hook_pre = value,
             Self::Wrapper => u.hook_wrapper = value,
             Self::Post => u.hook_post = value,

packages/oneclient_app/src/view/app/settings/minecraft.rs

@@ -38,6 +38,10 @@ impl Component for SettingsMinecraft {
             let v = profile.mem_max.map(|m| m.to_string()).unwrap_or_default();
             move || v
         });
+        let jvm_args = use_state({
+            let v = profile.launch_args.clone().unwrap_or_default();
+            move || v
+        });
         let pre_launch_command = use_state({
             let v = profile.hook_pre.clone().unwrap_or_default();
             move || v
@@ -58,6 +62,7 @@ impl Component for SettingsMinecraft {
                 &width.read(),
                 &height.read(),
                 &memory.read(),
+                &jvm_args.read(),
                 &pre_launch_command.read(),
                 &wrapper_command.read(),
                 &post_exit_command.read(),
@@ -89,6 +94,14 @@ impl Component for SettingsMinecraft {
                 "The amount of memory in megabytes allocated for the game.",
                 memory_field(memory),
             ))
+            .child(settings_row(
+                IconType::Terminal,
+                "JVM Arguments",
+                "Extra arguments passed to Java. Separate them with spaces; quote values containing spaces.",
+                TextInput::new(jvm_args)
+                    .placeholder("-XX:+UseG1GC")
+                    .width(Size::px(220.)),
+            ))
             .child(section_header("PROCESS"))
             .child(settings_row(
                 IconType::FilePlus02,
@@ -118,11 +131,13 @@ impl Component for SettingsMinecraft {
     }
 }
 
+#[allow(clippy::too_many_arguments)]
 fn build_update(
     fullscreen: bool,
     width: &str,
     height: &str,
     memory: &str,
+    jvm_args: &str,
     pre: &str,
     wrapper: &str,
     post: &str,
@@ -144,6 +159,7 @@ fn build_update(
         force_fullscreen: Patch::Set(fullscreen),
         resolution,
         mem_max,
+        launch_args: command_patch(jvm_args),
         hook_pre: command_patch(pre),
         hook_wrapper: command_patch(wrapper),
         hook_post: command_patch(post),

packages/oneclient_mc/src/arguments.rs

@@ -52,14 +52,49 @@ pub fn java_arguments(
     }
 
     parsed.push(format!("-Xmx{mem_max}M"));
-
-    if !custom_args.is_empty() {
-        parsed.push(custom_args);
-    }
+    parsed.extend(split_custom_args(&custom_args));
 
     Ok(parsed)
 }
 
+/// Splits a user-entered JVM argument string into individual arguments.
+///
+/// Whitespace-separated, with double quotes for values that contain spaces
+/// (`-Dfoo="a b"`), which is what people expect from every other launcher.
+/// Pushing the whole string as one argv entry, as this used to, means the JVM
+/// sees a single unrecognised option as soon as there is more than one.
+fn split_custom_args(raw: &str) -> Vec<String> {
+    let mut args = Vec::new();
+    let mut current = String::new();
+    let mut quoted = false;
+    let mut started = false;
+
+    for ch in raw.chars() {
+        match ch {
+            '"' => {
+                quoted = !quoted;
+                started = true;
+            }
+            c if c.is_whitespace() && !quoted => {
+                if started {
+                    args.push(std::mem::take(&mut current));
+                    started = false;
+                }
+            }
+            c => {
+                current.push(c);
+                started = true;
+            }
+        }
+    }
+
+    if started {
+        args.push(current);
+    }
+
+    args
+}
+
 #[allow(clippy::too_many_arguments)]
 pub fn minecraft_arguments(
     version_updated: bool,
@@ -415,3 +450,35 @@ where
 
     Ok(())
 }
+
+#[cfg(test)]
+mod tests {
+    use super::split_custom_args;
+
+    #[test]
+    fn blank_input_contributes_nothing() {
+        assert!(split_custom_args("").is_empty());
+        assert!(split_custom_args("   \t ").is_empty());
+    }
+
+    #[test]
+    fn each_flag_becomes_its_own_argument() {
+        assert_eq!(
+            split_custom_args("-XX:+UseG1GC  -Xms2G"),
+            vec!["-XX:+UseG1GC", "-Xms2G"]
+        );
+    }
+
+    #[test]
+    fn quotes_hold_a_value_with_spaces_together() {
+        assert_eq!(
+            split_custom_args(r#"-Dname="My Server" -Xss1M"#),
+            vec!["-Dname=My Server", "-Xss1M"]
+        );
+    }
+
+    #[test]
+    fn an_empty_quoted_value_survives() {
+        assert_eq!(split_custom_args(r#"-Dempty="""#), vec!["-Dempty="]);
+    }
+}