no branching allowed

src/core/stack.rs

@@ -11,15 +11,15 @@ pub struct Stack {
 impl Widget for Stack {
     fn draw(&mut self, painter: &mut Painter) {
         for _ in 0..self.offset {
-            painter.layer = painter.next_layer();
+            painter.next_layer();
         }
-        let base = painter.layer;
-        for child in &self.children {
-            painter.layer = if painter.layer == base {
-                painter.child_layer()
-            } else {
-                painter.next_layer()
-            };
+        let mut iter = self.children.iter();
+        if let Some(child) = iter.next() {
+            painter.child_layer();
+            painter.widget(child);
+        }
+        for child in iter {
+            painter.next_layer();
             painter.widget(child);
         }
     }

src/layout/painter.rs

@@ -291,12 +291,12 @@ impl<'a, 'c> Painter<'a, 'c> {
         self.ctx.text
     }
 
-    pub fn child_layer(&mut self) -> usize {
-        self.ctx.layers.child(self.layer)
+    pub fn child_layer(&mut self) {
+        self.layer = self.ctx.layers.child(self.layer);
     }
 
-    pub fn next_layer(&mut self) -> usize {
-        self.ctx.layers.next(self.layer)
+    pub fn next_layer(&mut self) {
+        self.layer = self.ctx.layers.next(self.layer);
     }
 }