span direction (sign) now works

src/layout/region.rs

@@ -40,10 +40,10 @@ impl UIPos {
         let anchor = self
             .anchor
             .lerp(region.top_left.anchor, region.bot_right.anchor);
-        let offset = self.offset;
-        // + self
-        //     .anchor
-        //     .lerp(region.top_left.offset, region.bot_right.offset);
+        let offset = self.offset
+            + self
+                .anchor
+                .lerp(region.top_left.offset, region.bot_right.offset);
         UIPos { anchor, offset }
     }
 
@@ -59,6 +59,16 @@ impl UIPos {
             },
         }
     }
+
+    pub fn flip(&mut self) {
+        self.anchor = 1.0 - self.anchor;
+        self.offset = -self.offset;
+    }
+
+    pub fn flipped(mut self) -> Self {
+        self.flip();
+        self
+    }
 }
 
 #[derive(Clone, Copy, Debug)]
@@ -133,6 +143,12 @@ impl UIRegion {
             bot_right: self.bot_right.axis_mut(axis),
         }
     }
+
+    pub fn flip(&mut self) {
+        self.top_left.flip();
+        self.bot_right.flip();
+        std::mem::swap(&mut self.top_left, &mut self.bot_right);
+    }
 }
 
 pub struct UIRegionAxisView<'a> {