Implementation of Godot's GDExtensionScriptInstance

Co-authored-by: Jan Haller <bromeon@gmail.com>
Co-authored-by: Lili Zoey <lili.andersen@nrk.no>

Author: 3 people

godot-codegen/src/codegen_special_cases.rs

@@ -158,6 +158,9 @@ const SELECTED_CLASSES: &[&str] = &[
     "ResourceLoader",
     "RigidBody2D",
     "SceneTree",
+    "Script",
+    "ScriptExtension",
+    "ScriptLanguage",
     "Sprite2D",
     "SpriteFrames",
     "TextServer",

godot-core/src/builtin/meta/mod.rs

@@ -273,3 +273,63 @@ impl PropertyInfo {
         }
     }
 }
+
+#[derive(Debug)]
+pub struct MethodInfo {
+    pub id: i32,
+    pub method_name: StringName,
+    pub class_name: ClassName,
+    pub return_type: PropertyInfo,
+    pub arguments: Vec<PropertyInfo>,
+    pub default_arguments: Vec<Variant>,
+    pub flags: global::MethodFlags,
+}
+
+impl MethodInfo {
+    /// Converts to the FFI type. Keep this object allocated while using that!
+    ///
+    /// The struct returned by this function contains pointers into the fields of `self`. `self` should therefore not be dropped while the
+    /// [`sys::GDExtensionMethodInfo`] is still in use.
+    ///
+    /// This function also leaks memory that has to be cleaned up by the caller once it is no longer used. Specifically the `arguments` and
+    /// `default_arguments` vectors have to be reconstructed from the pointer and length and then dropped/freed.
+    ///
+    /// Each vector can be reconstructed with `Vec::from_raw_parts` since the pointers were created with `Vec::into_boxed_slice`, which
+    /// guarantees that the vector capacity and length are equal.
+    pub fn method_sys(&self) -> sys::GDExtensionMethodInfo {
+        use crate::obj::EngineEnum as _;
+
+        let argument_count = self.arguments.len() as u32;
+        let argument_vec = self
+            .arguments
+            .iter()
+            .map(|arg| arg.property_sys())
+            .collect::<Vec<_>>()
+            .into_boxed_slice();
+
+        // SAFETY: dereferencing the new box pointer is fine as it is guaranteed to not be null
+        let arguments = unsafe { (*Box::into_raw(argument_vec)).as_mut_ptr() };
+
+        let default_argument_count = self.default_arguments.len() as u32;
+        let default_argument_vec = self
+            .default_arguments
+            .iter()
+            .map(|arg| arg.var_sys())
+            .collect::<Vec<_>>()
+            .into_boxed_slice();
+
+        // SAFETY: dereferencing the new box pointer is fine as it is guaranteed to not be null
+        let default_arguments = unsafe { (*Box::into_raw(default_argument_vec)).as_mut_ptr() };
+
+        sys::GDExtensionMethodInfo {
+            id: self.id,
+            name: self.method_name.string_sys(),
+            return_value: self.return_type.property_sys(),
+            argument_count,
+            arguments,
+            default_argument_count,
+            default_arguments,
+            flags: u32::try_from(self.flags.ord()).expect("flags should be valid"),
+        }
+    }
+}

godot-core/src/builtin/variant/mod.rs

@@ -236,7 +236,6 @@ impl Variant {
     /// # Safety
     /// `variant_ptr_array` must be a valid pointer to an array of `length` variant pointers.
     /// The caller is responsible of keeping the backing storage alive while the unbounded references exist.
-    #[cfg(since_api = "4.2")] // unused before
     pub(crate) unsafe fn unbounded_refs_from_sys<'a>(
         variant_ptr_array: *const sys::GDExtensionConstVariantPtr,
         length: usize,
@@ -253,6 +252,14 @@ impl Variant {
     pub(crate) fn ptr_from_sys_mut(variant_ptr: sys::GDExtensionVariantPtr) -> *mut Variant {
         variant_ptr as *mut Variant
     }
+
+    /// Move `self` into a system pointer. This transfers ownership and thus does not call the destructor.
+    ///
+    /// # Safety
+    /// `dst` must be a pointer to a [`Variant`] which is suitable for ffi with Godot.
+    pub(crate) unsafe fn move_var_ptr(self, dst: sys::GDExtensionVariantPtr) {
+        self.move_return_ptr(dst as *mut _, sys::PtrcallType::Standard);
+    }
 }
 
 // SAFETY:

godot-core/src/engine/mod.rs

@@ -19,8 +19,10 @@ pub use crate::gen::utilities;
 use crate::sys;
 
 mod gfile;
+mod script_instance;
 
 pub use gfile::{GFile, NotUniqueError};
+pub use script_instance::{create_script_instance, ScriptInstance};
 
 /// Support for Godot _native structures_.
 ///