feat: add Edge connection element and update RenderContext

Author: zty012

crates/project_graph/src/stage.rs

@@ -56,6 +56,8 @@ impl Stage {
                     zoom: self.camera.zoom(),
                     selected,
                     clicked: false,
+                    painter: painter.clone(),
+                    screen_center,
                 };
 
                 let element_size = element.world_rect().size() * self.camera.zoom();

crates/project_graph/src/stage/elements.rs

@@ -4,7 +4,10 @@ pub mod entities;
 
 use enum_dispatch::enum_dispatch;
 
-use crate::stage::{elements::entities::Entity, render_context::RenderContext};
+use crate::stage::{
+    elements::{connections::Connection, entities::Entity},
+    render_context::RenderContext,
+};
 
 /// 元素，以前称做舞台对象
 /// 所有可以被渲染的东西都应该实现这个 trait
@@ -22,4 +25,5 @@ pub trait ElementTrait {
 #[derive(knus::Decode, Debug, Clone)]
 pub enum Element {
     Entity(Entity),
+    Connection(Connection),
 }

crates/project_graph/src/stage/elements/connections.rs

@@ -1,10 +1,21 @@
+pub mod edge;
+
 use crate::stage::elements::ElementTrait;
+pub use edge::Edge;
+use enum_dispatch::enum_dispatch;
 
 /// 连接关系，连接节点端口的线段
 /// 不能被包含，不能被连接
+#[enum_dispatch]
 pub trait ConnectionTrait: ElementTrait {
     /// 起点端口 id
     fn from_port_id(&self) -> &str;
     /// 终点端口 id
     fn to_port_id(&self) -> &str;
 }
+
+#[enum_dispatch(ConnectionTrait, ElementTrait)]
+#[derive(knus::Decode, Debug, Clone)]
+pub enum Connection {
+    Edge(Edge),
+}

crates/project_graph/src/stage/elements/connections/edge.rs

@@ -0,0 +1,71 @@
+use nanoid::nanoid;
+use crate::stage::{
+    elements::{ElementTrait, connections::ConnectionTrait, entities::EntityTrait},
+    render_context::RenderContext,
+};
+
+#[derive(knus::Decode, Debug, Clone)]
+pub struct Edge {
+    #[knus(argument, default = nanoid!())]
+    id: String,
+    #[knus(child, unwrap(argument))]
+    from: String,
+    #[knus(child, unwrap(argument))]
+    to: String,
+}
+
+impl Edge {
+    pub fn new(id: String, from: String, to: String) -> Self {
+        Self { id, from, to }
+    }
+}
+
+impl ElementTrait for Edge {
+    fn id(&self) -> &str {
+        &self.id
+    }
+
+    fn ui(&self, _ui: &mut egui::Ui, rc: &mut RenderContext) {
+        // 暂存简单的线段和箭头绘制逻辑
+        // 由于当前架构下 Element::ui 无法直接访问 StageContext 查找 from/to 节点的 Position
+        // 我们这里先写好绘制逻辑，假设我们有了两个点
+    }
+
+    fn world_rect(&self) -> egui::Rect {
+        egui::Rect::NOTHING
+    }
+}
+
+impl Edge {
+    /// 辅助函数：绘制带箭头的线段
+    pub fn draw_arrow(painter: &egui::Painter, start: egui::Pos2, end: egui::Pos2, stroke: egui::Stroke) {
+        painter.line_segment([start, end], stroke);
+        
+        let vec = end - start;
+        let mag = vec.length();
+        if mag > 0.0 {
+            let dir = vec / mag;
+            let tip_size = 10.0 * stroke.width / 2.0; // 随粗细缩放
+            let side_dir = egui::vec2(dir.y, -dir.x);
+            
+            let p1 = end - dir * tip_size + side_dir * tip_size * 0.5;
+            let p2 = end - dir * tip_size - side_dir * tip_size * 0.5;
+            
+            painter.add(egui::Shape::convex_polygon(
+                vec![end, p1, p2],
+                stroke.color,
+                egui::Stroke::NONE,
+            ));
+        }
+    }
+}
+
+impl ConnectionTrait for Edge {
+    fn from_port_id(&self) -> &str {
+        &self.from
+    }
+
+    fn to_port_id(&self) -> &str {
+        &self.to
+    }
+}

crates/project_graph/src/stage/render_context.rs

@@ -1,7 +1,11 @@
+use egui::Pos2;
+
 pub struct RenderContext {
     pub zoom: f32,
     pub selected: bool,
     pub clicked: bool,
+    pub painter: egui::Painter,
+    pub screen_center: Pos2,
 }
 
 impl RenderContext {}