gstreamer/iterator: Store filter types in a hash table

Static variables in generic functions only exist once and not once per
type parameter, so before we were only able to register exactly one
filter type.

gstreamer/src/iterator.rs

@@ -358,38 +358,51 @@ unsafe extern "C" fn filter_boxed_unref<T: 'static>(boxed: gpointer) {
 }
 
 unsafe extern "C" fn filter_boxed_get_type<T: StaticType + 'static>() -> glib_sys::GType {
-    use std::sync::Once;
+    use once_cell::sync::Lazy;
+    use std::collections::HashMap;
+    use std::sync::Mutex;
 
-    static mut TYPE: glib_sys::GType = gobject_sys::G_TYPE_INVALID;
-    static ONCE: Once = Once::new();
+    static mut TYPES: Lazy<Mutex<HashMap<String, glib_sys::GType>>> =
+        Lazy::new(|| Mutex::new(HashMap::new()));
 
-    ONCE.call_once(|| {
-        let type_name = {
+    let mut types = TYPES.lock().unwrap();
+    let type_name = T::static_type().name();
+
+    if let Some(type_) = types.get(&type_name) {
+        return *type_;
+    }
+
+    let type_ = {
+        let iter_type_name = {
             let mut idx = 0;
 
             loop {
-                let type_name = CString::new(format!(
-                    "GstRsIteratorFilterBoxed-{}-{}",
-                    T::static_type().name(),
-                    idx
-                ))
-                .unwrap();
-                if gobject_sys::g_type_from_name(type_name.as_ptr()) == gobject_sys::G_TYPE_INVALID
+                let iter_type_name =
+                    CString::new(format!("GstRsIteratorFilterBoxed-{}-{}", type_name, idx))
+                        .unwrap();
+                if gobject_sys::g_type_from_name(iter_type_name.as_ptr())
+                    == gobject_sys::G_TYPE_INVALID
                 {
-                    break type_name;
+                    break iter_type_name;
                 }
                 idx += 1;
             }
         };
 
-        TYPE = gobject_sys::g_boxed_type_register_static(
-            type_name.as_ptr(),
+        let type_ = gobject_sys::g_boxed_type_register_static(
+            iter_type_name.as_ptr(),
             Some(filter_boxed_ref::<T>),
             Some(filter_boxed_unref::<T>),
         );
-    });
 
-    TYPE
+        assert_ne!(type_, gobject_sys::G_TYPE_INVALID);
+
+        type_
+    };
+
+    types.insert(type_name, type_);
+
+    type_
 }
 
 unsafe extern "C" fn find_trampoline<T, F: FnMut(T) -> bool>(