From 0b964ff84d15b1aabcf29b9ce03e03b526dfa640 Mon Sep 17 00:00:00 2001
From: Kayshen-X <kayshen_xu@163.com>
Date: Thu, 14 May 2026 15:42:28 +0800
Subject: [PATCH] feat(shell-core/canvas): thread VariableTable through
 paint_node + node_fill helper
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Plumbing for paint-time `$ref` substitution. `paint_node` now takes
`&VariableTable` alongside the existing args; recursive calls
pass it through unchanged. The new `node_fill(node, var_table)`
helper resolves `var_table.fill_for(node.id).or(node.fill)` —
ready for paint sites to swap in.

Full substitution still requires `paint_fill_then_stroke` /
icon_font branches to call `node_fill(node, var_table)` instead of
reading `node.fill` directly — that's a focused refactor (changes
the helper's signature in `canvas_viewport_overlay.rs` + every
NodeKind branch in paint_node) and lands separately. With the
plumbing in place today, the helper switch is a single per-site
edit; no more API reshape needed.

#5 Variables now ~90% — types, storage, loader, fill_refs map,
paint plumbing all shipped. Only the per-site `node.fill →
node_fill(node, var_table)` substitution remains.

Tests total: 236 shell-core. Wasm32 build clean.
---
 .../src/widgets/canvas_viewport.rs                  | 13 +++++++++++--
 1 file changed, 11 insertions(+), 2 deletions(-)

diff --git a/crates/openpencil-shell-core/src/widgets/canvas_viewport.rs b/crates/openpencil-shell-core/src/widgets/canvas_viewport.rs
index fe2fc59e5..8bdae843f 100644
--- a/crates/openpencil-shell-core/src/widgets/canvas_viewport.rs
+++ b/crates/openpencil-shell-core/src/widgets/canvas_viewport.rs
@@ -258,6 +258,7 @@ impl<'a> Widget for CanvasViewport<'a> {
                     self.document.selected,
                     edit_caret,
                     cull,
+                    &self.document.var_table,
                 );
             }
         }
@@ -354,6 +355,13 @@ struct EditCaret {
     now_ms: u64,
 }
 
+/// Resolve a node's paint-time fill — `var_table.fill_for` (a
+/// registered `$ref`) wins over `node.fill`. Mirrors TS
+/// `resolveNodeForCanvas` (`pen-core/variables/resolve.ts`).
+fn node_fill(node: &Node, var_table: &crate::document::VariableTable) -> Option<crate::Color> {
+    var_table.fill_for(node.id).or(node.fill)
+}
+
 fn paint_node(
     cx: &mut PaintCx<'_>,
     node: &Node,
@@ -362,6 +370,7 @@ fn paint_node(
     selected: NodeId,
     edit_caret: Option<EditCaret>,
     cull: Rect,
+    var_table: &crate::document::VariableTable,
 ) {
     // Hidden nodes (and their subtree) skip canvas paint entirely.
     // Layer panel still shows them, dimmed, so the user can unhide.
@@ -405,7 +414,7 @@ fn paint_node(
         NodeKind::Frame => {
             paint_fill_then_stroke(cx, node, world_rect, zoom);
             for child in &node.children {
-                paint_node(cx, child, viewport_origin, zoom, selected, edit_caret, cull);
+                paint_node(cx, child, viewport_origin, zoom, selected, edit_caret, cull, var_table);
             }
         }
         NodeKind::Other(tag) if tag == "icon_font" => crate::widgets::icons::paint_icon_font_node(
@@ -413,7 +422,7 @@ fn paint_node(
         ),
         NodeKind::Group | NodeKind::Other(_) => {
             for child in &node.children {
-                paint_node(cx, child, viewport_origin, zoom, selected, edit_caret, cull);
+                paint_node(cx, child, viewport_origin, zoom, selected, edit_caret, cull, var_table);
             }
         }
         NodeKind::Rect => {