Extract borrow of FontSystem from Buffer

src/font/system/mod.rs

@@ -1,3 +1,5 @@
+use core::ops::{Deref, DerefMut};
+
 #[cfg(not(feature = "std"))]
 pub use self::no_std::*;
 #[cfg(not(feature = "std"))]
@@ -10,3 +12,22 @@ mod std;
 
 // re-export fontdb
 pub use fontdb;
+
+pub struct BorrowedWithFontSystem<'a, T> {
+    pub(crate) inner: &'a mut T,
+    pub(crate) font_system: &'a FontSystem,
+}
+
+impl<'a, T> Deref for BorrowedWithFontSystem<'a, T> {
+    type Target = T;
+
+    fn deref(&self) -> &Self::Target {
+        self.inner
+    }
+}
+
+impl<'a, T> DerefMut for BorrowedWithFontSystem<'a, T> {
+    fn deref_mut(&mut self) -> &mut Self::Target {
+        self.inner
+    }
+}