From 1f05ea431ea59caf06c80a07f005c141b841e6e7 Mon Sep 17 00:00:00 2001
From: Julian Orth <ju.orth@gmail.com>
Date: Mon, 4 Apr 2022 23:44:25 +0200
Subject: [PATCH] autocommit 2022-04-04 23:44:25 CEST

---
 src/rect.rs        |  2 +-
 src/rect/region.rs | 38 +++++++++++++++++++++++---------------
 2 files changed, 24 insertions(+), 16 deletions(-)

diff --git a/src/rect.rs b/src/rect.rs
index 20a15d82..0e344be2 100644
--- a/src/rect.rs
+++ b/src/rect.rs
@@ -17,7 +17,7 @@ pub struct Rect {
 
 type Container = SmallVec<[Rect; 1]>;
 
-#[derive(Default)]
+#[derive(Default, Clone)]
 pub struct Region {
     rects: Container,
     extents: Rect,
diff --git a/src/rect/region.rs b/src/rect/region.rs
index b83a3700..11298dc4 100644
--- a/src/rect/region.rs
+++ b/src/rect/region.rs
@@ -8,43 +8,52 @@ use std::ops::Deref;
 use std::rc::Rc;
 
 impl Region {
-    pub fn new(rect: Rect) -> Self {
+    pub fn new(rect: Rect) -> Rc<Self> {
         let mut rects = SmallVec::new();
         rects.push(rect);
-        Self {
+        Rc::new(Self {
             rects,
             extents: rect,
-        }
+        })
     }
 
-    pub fn from_rects(rects: &[Rect]) -> Self {
+    pub fn from_rects(rects: &[Rect]) -> Rc<Self> {
         if rects.is_empty() {
-            return Self::default();
+            return Rc::new(Self::default());
         }
         if rects.len() == 1 {
             return Self::new(rects[0]);
         }
         let rects = rects_to_bands(rects);
-        Self {
+        Rc::new(Self {
             extents: extents(&rects),
             rects,
-        }
+        })
     }
 
-    pub fn union(&self, other: &Self) -> Self {
+    pub fn union(self: &Rc<Self>, other: &Rc<Self>) -> Rc<Self> {
+        if self.extents.is_empty() {
+            return other.clone();
+        }
+        if other.extents.is_empty() {
+            return self.clone();
+        }
         let rects = op::<Union>(&self.rects, &other.rects);
-        Self {
+        Rc::new(Self {
             rects,
             extents: self.extents.union(other.extents),
-        }
+        })
     }
 
-    pub fn subtract(&self, other: &Self) -> Self {
+    pub fn subtract(self: &Rc<Self>, other: &Rc<Self>) -> Rc<Self> {
+        if self.extents.is_empty() || other.extents.is_empty() {
+            return self.clone();
+        }
         let rects = op::<Subtract>(&self.rects, &other.rects);
-        Self {
+        Rc::new(Self {
             extents: extents(&rects),
             rects,
-        }
+        })
     }
 
     pub fn extents(&self) -> Rect {
@@ -562,10 +571,9 @@ impl RegionBuilder {
             return;
         }
         let region = Region::from_rects(&self.pending);
-        let base = match self.op {
+        self.base = match self.op {
             BuilderOp::Add => self.base.union(&region),
             BuilderOp::Sub => self.base.subtract(&region),
         };
-        self.base = Rc::new(base);
     }
 }