prepare for layouting

src/main.rs

@@ -22,7 +22,7 @@ use glutin::{
 };
 use taffy::Taffy;
 use weak_table::PtrWeakKeyHashMap;
-use crate::nodes::{Node, render_recursively, RenderContext};
+use crate::nodes::{layout_recursively, Node, render_recursively, RenderContext};
 
 mod nodes;
 
@@ -48,7 +48,9 @@ fn main() {
     taffy_map.insert(root.clone(), root_node);
 
     let mut context = RenderContext {
-        canvas
+        canvas,
+        taffy_map,
+        taffy
     };
 
     event_loop.run(move |event, _target, control_flow| match event {
@@ -66,7 +68,16 @@ fn main() {
             _ => {}
         },
         Event::RedrawRequested(_) => {
-            render(&buffer_context, &surface, &window, &mut context, &root, &taffy_map, &taffy);
+            layout_recursively(&root, &mut context);
+            let src_nodes = context.taffy_map.values().map(|v| v.to_owned()).collect::<Vec<_>>();
+            context.taffy_map.remove_expired();
+            let dst_nodes = context.taffy_map.values().map(|v| v.to_owned()).collect::<Vec<_>>();
+            for src_node in src_nodes {
+                if !dst_nodes.contains(&src_node) {
+                    context.taffy.remove(src_node).unwrap();
+                }
+            }
+            render(&buffer_context, &surface, &window, &mut context, &root);
         },
         _ => {}
     })
@@ -115,9 +126,7 @@ fn render(
     surface: &Surface<WindowSurface>,
     window: &Window,
     context: &mut RenderContext<OpenGl>,
-    root_node: &Arc<GNode>,
-    taffy_map: &TaffyMap,
-    taffy: &Taffy
+    root_node: &Arc<GNode>
 ) {
     // Make sure the canvas has the right size:
     let size = window.inner_size();
@@ -126,7 +135,7 @@ fn render(
     context.canvas.clear_rect(0, 0, size.width, size.height, Color::black());
 
     // Do the render passes here
-    render_recursively(root_node, context, taffy_map, taffy);
+    render_recursively(root_node, context);
 
     // Tell renderer to execute all drawing commands
     context.canvas.flush();

src/nodes/layout.rs

@@ -0,0 +1,32 @@
+use femtovg::Renderer;
+use crate::nodes::{Node, NodeChildren, Overflow, RenderContext, Style};
+use taffy::style::{Style as TaffyStyle};
+
+pub struct Layout<T> {
+    style: Style,
+    children: NodeChildren<T>
+}
+
+impl<T: Renderer> Layout<T> {
+    pub(crate) fn new() -> Layout<T> {
+        Layout {
+            style: Style {
+                layout: TaffyStyle::default(),
+                overflow: Overflow::Visible
+            },
+            children: NodeChildren::new()
+        }
+    }
+}
+
+impl<T: Renderer> Node<T> for Layout<T> {
+    fn style(&self) -> &Style {
+        &self.style
+    }
+    fn children(&self) -> Option<&NodeChildren<T>> {
+        Some(&self.children)
+    }
+    fn render(&self, context: &mut RenderContext<T>, _layout: taffy::layout::Layout, render_children: &dyn Fn(&mut RenderContext<T>)) {
+        render_children(context);
+    }
+}

src/nodes/mod.rs

@@ -1,3 +1,5 @@
+pub mod layout;
+
 use std::sync::Arc;
 use femtovg::{Canvas, Color, Renderer};
 use femtovg::renderer::OpenGl;
@@ -9,7 +11,9 @@ use taffy::Taffy;
 use crate::{GNode, TaffyMap};
 
 pub struct RenderContext<T: Renderer> {
-    pub(crate) canvas: Canvas<T>,
+    pub canvas: Canvas<T>,
+    pub taffy_map: TaffyMap,
+    pub taffy: Taffy
 }
 
 #[derive(Copy, Clone, Default)]
@@ -39,14 +43,41 @@ pub trait Node<T: Renderer> {
     fn children(&self) -> Option<&NodeChildren<T>>;
     /// Render the node and its children. render_children gets ['children'] and calls this function there as well. When drawing, the canvas is translated to the node's location.
     /// Canvas considers 0, 0 to be top left corner (for location after layouting happens)
-    fn render(&self, context: &mut RenderContext<T>, layout: &Layout, render_children: &dyn Fn(&mut RenderContext<T>));
+    fn render(&self, context: &mut RenderContext<T>, layout: Layout, render_children: &dyn Fn(&mut RenderContext<T>));
 }
 
-pub fn render_recursively(selfref: &Arc<GNode>, context: &mut RenderContext<OpenGl>, taffy_map: &TaffyMap, taffy: &Taffy) {
-    let styles = selfref.style();
-    let node = taffy_map.get(selfref).unwrap();
-    let layout = taffy.layout(*node).unwrap();
-    let sself = selfref.clone();
+pub fn layout_recursively(node: &Arc<GNode>, context: &mut RenderContext<OpenGl>) -> taffy::node::Node {
+    let taffy_node = context.taffy_map.get(node);
+    let taffy_node = match taffy_node {
+        Some(taffy_node) => taffy_node,
+        None => {
+            let taffy_node = context.taffy.new_leaf(node.style().layout.to_owned()).unwrap();
+            context.taffy_map.insert(node.clone(), taffy_node);
+            context.taffy_map.get(node).unwrap()
+        }
+    };
+
+    let taffy_node = taffy_node.to_owned();
+
+    match node.children() {
+        None => {},
+        Some(children) => {
+            let mut t_children = Vec::with_capacity(children.len());
+            for child in children {
+                t_children.push(layout_recursively(child, context).to_owned());
+            }
+            context.taffy.set_children(taffy_node, t_children.as_slice()).unwrap();
+        }
+    }
+
+    taffy_node
+}
+
+pub fn render_recursively(node: &Arc<GNode>, context: &mut RenderContext<OpenGl>) {
+    let styles = node.style();
+    let taffy_node = context.taffy_map.get(node).unwrap();
+    let layout = *context.taffy.layout(*taffy_node).unwrap();
+    let sself = node.clone();
     context.canvas.save();
     context.canvas.translate(layout.location.x, layout.location.y);
     match styles.overflow {
@@ -63,7 +94,7 @@ pub fn render_recursively(selfref: &Arc<GNode>, context: &mut RenderContext<Open
     sself.render(context, layout, & (|context| {
         if let Some(children) = sself.children() {
             for child in children {
-                render_recursively(child, context, taffy_map, taffy);
+                render_recursively(child, context);
             }
         }
     }));
@@ -98,7 +129,7 @@ impl<T: Renderer> Node<T> for RedBoxDemo {
     fn children(&self) -> Option<&NodeChildren<T>> {
         None
     }
-    fn render<'a>(&self, context: &mut RenderContext<T>, _layout: &Layout, _render_children: &dyn Fn(&mut RenderContext<T>)) {
+    fn render(&self, context: &mut RenderContext<T>, _layout: Layout, _render_children: &dyn Fn(&mut RenderContext<T>)) {
         context.canvas.clear_rect(
             0,
             0,