"Traitify" the Style struct (#568)

* Create style traits

* Add algorithm-specific PartialLayoutTree traits

* Taffy tree changes

* Convert algorithms to traitified styles

* Remove style clone in grid algorithm

* Fixup convert

* Make CacheMut an associated type

* Update examples to use new traits

* Fix --no-default-features

* Fixup is_block

* Fix clippy lints

* Fix --no-default-features taffy_tree

* Give style trait associated types unique names

Author: nicoburns

examples/custom_tree_owned_partial.rs

@@ -126,7 +126,12 @@ impl taffy::TraversePartialTree for Node {
 }
 
 impl taffy::LayoutPartialTree for Node {
-    fn get_style(&self, node_id: NodeId) -> &Style {
+    type CoreContainerStyle<'a> = &'a Style where
+        Self: 'a;
+
+    type CacheMut<'b> = &'b mut Cache where Self: 'b;
+
+    fn get_core_container_style(&self, node_id: NodeId) -> Self::CoreContainerStyle<'_> {
         &self.node_from_id(node_id).style
     }
 
@@ -162,6 +167,38 @@ impl taffy::LayoutPartialTree for Node {
     }
 }
 
+impl taffy::LayoutFlexboxContainer for Node {
+    type FlexboxContainerStyle<'a> = &'a Style where
+        Self: 'a;
+
+    type FlexboxItemStyle<'a> = &'a Style where
+        Self: 'a;
+
+    fn get_flexbox_container_style(&self, node_id: NodeId) -> Self::FlexboxContainerStyle<'_> {
+        &self.node_from_id(node_id).style
+    }
+
+    fn get_flexbox_child_style(&self, child_node_id: NodeId) -> Self::FlexboxItemStyle<'_> {
+        &self.node_from_id(child_node_id).style
+    }
+}
+
+impl taffy::LayoutGridContainer for Node {
+    type GridContainerStyle<'a> = &'a Style where
+        Self: 'a;
+
+    type GridItemStyle<'a> = &'a Style where
+        Self: 'a;
+
+    fn get_grid_container_style(&self, node_id: NodeId) -> Self::GridContainerStyle<'_> {
+        &self.node_from_id(node_id).style
+    }
+
+    fn get_grid_child_style(&self, child_node_id: NodeId) -> Self::GridItemStyle<'_> {
+        &self.node_from_id(child_node_id).style
+    }
+}
+
 fn main() -> Result<(), taffy::TaffyError> {
     let mut root = Node::new_column(Style::DEFAULT);
 

examples/custom_tree_owned_unsafe.rs

@@ -130,7 +130,12 @@ impl TraversePartialTree for StatelessLayoutTree {
 impl TraverseTree for StatelessLayoutTree {}
 
 impl LayoutPartialTree for StatelessLayoutTree {
-    fn get_style(&self, node_id: NodeId) -> &Style {
+    type CoreContainerStyle<'a> = &'a Style where
+        Self: 'a;
+
+    type CacheMut<'b> = &'b mut Cache where Self: 'b;
+
+    fn get_core_container_style(&self, node_id: NodeId) -> Self::CoreContainerStyle<'_> {
         unsafe { &node_from_id(node_id).style }
     }
 
@@ -166,6 +171,38 @@ impl LayoutPartialTree for StatelessLayoutTree {
     }
 }
 
+impl taffy::LayoutFlexboxContainer for StatelessLayoutTree {
+    type FlexboxContainerStyle<'a> = &'a Style where
+        Self: 'a;
+
+    type FlexboxItemStyle<'a> = &'a Style where
+        Self: 'a;
+
+    fn get_flexbox_container_style(&self, node_id: NodeId) -> Self::FlexboxContainerStyle<'_> {
+        unsafe { &node_from_id(node_id).style }
+    }
+
+    fn get_flexbox_child_style(&self, child_node_id: NodeId) -> Self::FlexboxItemStyle<'_> {
+        unsafe { &node_from_id(child_node_id).style }
+    }
+}
+
+impl taffy::LayoutGridContainer for StatelessLayoutTree {
+    type GridContainerStyle<'a> = &'a Style where
+        Self: 'a;
+
+    type GridItemStyle<'a> = &'a Style where
+        Self: 'a;
+
+    fn get_grid_container_style(&self, node_id: NodeId) -> Self::GridContainerStyle<'_> {
+        unsafe { &node_from_id(node_id).style }
+    }
+
+    fn get_grid_child_style(&self, child_node_id: NodeId) -> Self::GridItemStyle<'_> {
+        unsafe { &node_from_id(child_node_id).style }
+    }
+}
+
 impl RoundTree for StatelessLayoutTree {
     fn get_unrounded_layout(&self, node_id: NodeId) -> &Layout {
         unsafe { &node_from_id_mut(node_id).unrounded_layout }

examples/custom_tree_vec.rs

@@ -139,7 +139,12 @@ impl taffy::TraversePartialTree for Tree {
 impl taffy::TraverseTree for Tree {}
 
 impl taffy::LayoutPartialTree for Tree {
-    fn get_style(&self, node_id: NodeId) -> &Style {
+    type CoreContainerStyle<'a> = &'a Style where
+        Self: 'a;
+
+    type CacheMut<'b> = &'b mut Cache where Self: 'b;
+
+    fn get_core_container_style(&self, node_id: NodeId) -> Self::CoreContainerStyle<'_> {
         &self.node_from_id(node_id).style
     }
 
@@ -175,6 +180,38 @@ impl taffy::LayoutPartialTree for Tree {
     }
 }
 
+impl taffy::LayoutFlexboxContainer for Tree {
+    type FlexboxContainerStyle<'a> = &'a Style where
+        Self: 'a;
+
+    type FlexboxItemStyle<'a> = &'a Style where
+        Self: 'a;
+
+    fn get_flexbox_container_style(&self, node_id: NodeId) -> Self::FlexboxContainerStyle<'_> {
+        &self.node_from_id(node_id).style
+    }
+
+    fn get_flexbox_child_style(&self, child_node_id: NodeId) -> Self::FlexboxItemStyle<'_> {
+        &self.node_from_id(child_node_id).style
+    }
+}
+
+impl taffy::LayoutGridContainer for Tree {
+    type GridContainerStyle<'a> = &'a Style where
+        Self: 'a;
+
+    type GridItemStyle<'a> = &'a Style where
+        Self: 'a;
+
+    fn get_grid_container_style(&self, node_id: NodeId) -> Self::GridContainerStyle<'_> {
+        &self.node_from_id(node_id).style
+    }
+
+    fn get_grid_child_style(&self, child_node_id: NodeId) -> Self::GridItemStyle<'_> {
+        &self.node_from_id(child_node_id).style
+    }
+}
+
 impl taffy::RoundTree for Tree {
     fn get_unrounded_layout(&self, node_id: NodeId) -> &Layout {
         &self.node_from_id(node_id).unrounded_layout