1 files changed, 116 insertions, 0 deletions
diff --git a/graphics/src/geometry/cache.rs b/graphics/src/geometry/cache.rs
new file mode 100644
index 00000000..d70cee0b
--- /dev/null
+++ b/graphics/src/geometry/cache.rs
@@ -0,0 +1,116 @@
+use crate::cache::{self, Cached};
+use crate::core::Size;
+use crate::geometry::{self, Frame};
+
+pub use cache::Group;
+
+/// A simple cache that stores generated geometry to avoid recomputation.
+///
+/// A [`Cache`] will not redraw its geometry unless the dimensions of its layer
+/// change or it is explicitly cleared.
+pub struct Cache<Renderer>
+where
+    Renderer: geometry::Renderer,
+{
+    raw: crate::Cache<Data<<Renderer::Geometry as Cached>::Cache>>,
+}
+
+#[derive(Debug, Clone)]
+struct Data<T> {
+    bounds: Size,
+    geometry: T,
+}
+
+impl<Renderer> Cache<Renderer>
+where
+    Renderer: geometry::Renderer,
+{
+    /// Creates a new empty [`Cache`].
+    pub fn new() -> Self {
+        Cache {
+            raw: cache::Cache::new(),
+        }
+    }
+
+    /// Creates a new empty [`Cache`] with the given [`Group`].
+    ///
+    /// Caches within the same group may reuse internal rendering storage.
+    ///
+    /// You should generally group caches that are likely to change
+    /// together.
+    pub fn with_group(group: Group) -> Self {
+        Cache {
+            raw: crate::Cache::with_group(group),
+        }
+    }
+
+    /// Clears the [`Cache`], forcing a redraw the next time it is used.
+    pub fn clear(&self) {
+        self.raw.clear();
+    }
+
+    /// Draws geometry using the provided closure and stores it in the
+    /// [`Cache`].
+    ///
+    /// The closure will only be called when
+    /// - the bounds have changed since the previous draw call.
+    /// - the [`Cache`] is empty or has been explicitly cleared.
+    ///
+    /// Otherwise, the previously stored geometry will be returned. The
+    /// [`Cache`] is not cleared in this case. In other words, it will keep
+    /// returning the stored geometry if needed.
+    pub fn draw(
+        &self,
+        renderer: &Renderer,
+        bounds: Size,
+        draw_fn: impl FnOnce(&mut Frame<Renderer>),
+    ) -> Renderer::Geometry {
+        use std::ops::Deref;
+
+        let state = self.raw.state();
+
+        let previous = match state.borrow().deref() {
+            cache::State::Empty { previous } => {
+                previous.as_ref().map(|data| data.geometry.clone())
+            }
+            cache::State::Filled { current } => {
+                if current.bounds == bounds {
+                    return Cached::load(&current.geometry);
+                }
+
+                Some(current.geometry.clone())
+            }
+        };
+
+        let mut frame = Frame::new(renderer, bounds);
+        draw_fn(&mut frame);
+
+        let geometry = frame.into_geometry().cache(self.raw.group(), previous);
+        let result = Cached::load(&geometry);
+
+        *state.borrow_mut() = cache::State::Filled {
+            current: Data { bounds, geometry },
+        };
+
+        result
+    }
+}
+
+impl<Renderer> std::fmt::Debug for Cache<Renderer>
+where
+    Renderer: geometry::Renderer,
+    <Renderer::Geometry as Cached>::Cache: std::fmt::Debug,
+{
+    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        write!(f, "{:?}", &self.raw)
+    }
+}
+
+impl<Renderer> Default for Cache<Renderer>
+where
+    Renderer: geometry::Renderer,
+{
+    fn default() -> Self {
+        Self::new()
+    }
+}