1 files changed, 125 insertions, 0 deletions
diff --git a/renderer/src/geometry/cache.rs b/renderer/src/geometry/cache.rs
new file mode 100644
index 00000000..d82e7f69
--- /dev/null
+++ b/renderer/src/geometry/cache.rs
@@ -0,0 +1,125 @@
+use crate::core::Size;
+use crate::geometry::{Frame, Geometry};
+use crate::Renderer;
+
+use std::cell::RefCell;
+use std::sync::Arc;
+
+/// 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.
+#[derive(Debug, Default)]
+pub struct Cache {
+    state: RefCell<State>,
+}
+
+#[derive(Debug, Default)]
+enum State {
+    #[default]
+    Empty,
+    Filled {
+        bounds: Size,
+        primitive: Internal,
+    },
+}
+
+#[derive(Debug, Clone)]
+enum Internal {
+    TinySkia(Arc<iced_tiny_skia::Primitive>),
+    #[cfg(feature = "wgpu")]
+    Wgpu(Arc<iced_wgpu::Primitive>),
+}
+
+impl Cache {
+    /// Creates a new empty [`Cache`].
+    pub fn new() -> Self {
+        Cache {
+            state: Default::default(),
+        }
+    }
+
+    /// Clears the [`Cache`], forcing a redraw the next time it is used.
+    pub fn clear(&self) {
+        *self.state.borrow_mut() = State::Empty;
+    }
+
+    /// 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<Theme>(
+        &self,
+        renderer: &Renderer<Theme>,
+        bounds: Size,
+        draw_fn: impl FnOnce(&mut Frame),
+    ) -> Geometry {
+        use std::ops::Deref;
+
+        if let State::Filled {
+            bounds: cached_bounds,
+            primitive,
+        } = self.state.borrow().deref()
+        {
+            if *cached_bounds == bounds {
+                match primitive {
+                    Internal::TinySkia(primitive) => {
+                        return Geometry::TinySkia(
+                            iced_tiny_skia::Primitive::Cache {
+                                content: primitive.clone(),
+                            },
+                        );
+                    }
+                    #[cfg(feature = "wgpu")]
+                    Internal::Wgpu(primitive) => {
+                        return Geometry::Wgpu(iced_wgpu::Primitive::Cache {
+                            content: primitive.clone(),
+                        });
+                    }
+                }
+            }
+        }
+
+        let mut frame = Frame::new(renderer, bounds);
+        draw_fn(&mut frame);
+
+        let primitive = {
+            let geometry = frame.into_geometry();
+
+            match geometry {
+                Geometry::TinySkia(primitive) => {
+                    Internal::TinySkia(Arc::new(primitive))
+                }
+                #[cfg(feature = "wgpu")]
+                Geometry::Wgpu(primitive) => {
+                    Internal::Wgpu(Arc::new(primitive))
+                }
+            }
+        };
+
+        *self.state.borrow_mut() = State::Filled {
+            bounds,
+            primitive: primitive.clone(),
+        };
+
+        match primitive {
+            Internal::TinySkia(primitive) => {
+                Geometry::TinySkia(iced_tiny_skia::Primitive::Cache {
+                    content: primitive,
+                })
+            }
+            #[cfg(feature = "wgpu")]
+            Internal::Wgpu(primitive) => {
+                Geometry::Wgpu(iced_wgpu::Primitive::Cache {
+                    content: primitive,
+                })
+            }
+        }
+    }
+}