feat(ecs): add stopping event loop

1 files changed, 66 insertions, 0 deletions

diff --git a/ecs/src/flags.rs b/ecs/src/flags.rs
new file mode 100644
index 0000000..ad10a0f
--- /dev/null
+++ b/ecs/src/flags.rs
@@ -0,0 +1,66 @@
+use std::any::Any;
+
+use crate::lock::WriteGuard;
+use crate::system::{
+    NoInitParamFlag as NoInitSystemParamFlag,
+    Param as SystemParam,
+    System,
+};
+use crate::tuple::FilterExclude as TupleFilterExclude;
+use crate::{WorldData, WorldFlags};
+
+#[derive(Debug)]
+pub struct Flags<'world>
+{
+    world_flags: WriteGuard<'world, WorldFlags>,
+}
+
+impl<'world> Flags<'world>
+{
+    /// Calling this function makes the loop in [`Engine::event_loop`] stop at the next
+    /// opportune time.
+    pub fn stop(&mut self)
+    {
+        self.world_flags.stop = true;
+    }
+}
+
+unsafe impl<'world> SystemParam<'world> for Flags<'world>
+{
+    type Flags = NoInitSystemParamFlag;
+    type Input = TupleFilterExclude;
+
+    fn initialize<SystemImpl>(
+        _system: &mut impl System<'world, SystemImpl>,
+        _input: Self::Input,
+    )
+    {
+    }
+
+    fn new<SystemImpl>(
+        _system: &'world impl System<'world, SystemImpl>,
+        world_data: &'world WorldData,
+    ) -> Self
+    {
+        Self {
+            world_flags: world_data
+                .flags
+                .write_nonblock()
+                .expect("Failed to acquire read-write world flags lock"),
+        }
+    }
+
+    fn is_compatible<Other: SystemParam<'world>>() -> bool
+    {
+        let other_comparable = Other::get_comparable();
+
+        other_comparable.downcast_ref::<Comparable>().is_none()
+    }
+
+    fn get_comparable() -> Box<dyn Any>
+    {
+        Box::new(Comparable)
+    }
+}
+
+struct Comparable;