From b97a567eb76ad2581b2bf4e56dcf5b5d195aa20d Mon Sep 17 00:00:00 2001
From: KOKI <nekomehako@gmail.com>
Date: Mon, 1 Aug 2022 16:54:00 +0900
Subject: [PATCH] Snap Connections and Ports

---
 egui_node_graph/src/editor_ui.rs | 46 +++++++++++++++++++++++++++++---
 1 file changed, 42 insertions(+), 4 deletions(-)

diff --git a/egui_node_graph/src/editor_ui.rs b/egui_node_graph/src/editor_ui.rs
index a64f144..505fdcf 100644
--- a/egui_node_graph/src/editor_ui.rs
+++ b/egui_node_graph/src/editor_ui.rs
@@ -8,6 +8,7 @@ use egui::epaint::{CubicBezierShape, RectShape};
 use egui::*;
 
 pub type PortLocations = std::collections::HashMap<AnyParameterId, Pos2>;
+const DISTANCE_TO_CONNECT: f32 = 10.0;
 
 /// Nodes communicate certain events to the parent graph when drawn. There is
 /// one special `User` variant which can be used by users as the return value
@@ -176,8 +177,37 @@ where
             let connection_color = port_type.data_type_color(&self.user_state);
             let start_pos = port_locations[locator];
             let (src_pos, dst_pos) = match locator {
-                AnyParameterId::Output(_) => (start_pos, cursor_pos),
-                AnyParameterId::Input(_) => (cursor_pos, start_pos),
+                AnyParameterId::Output(_) => {
+                    // Find a port to connect to
+                    let port = self.graph.inputs.iter().find_map(|(input_id, _)| {
+                        let port_pos = port_locations[&AnyParameterId::Input(input_id)];
+                        if port_pos.distance(cursor_pos) < DISTANCE_TO_CONNECT {
+                            Some(port_pos)
+                        } else {
+                            None
+                        }
+                    });
+                    if let Some(port_pos) = port {
+                        (start_pos, port_pos)
+                    } else {
+                        (start_pos, cursor_pos)
+                    }
+                }
+                AnyParameterId::Input(_) => {
+                    let port = self.graph.outputs.iter().find_map(|(output_id, _)| {
+                        let port_pos = port_locations[&AnyParameterId::Output(output_id)];
+                        if port_pos.distance(cursor_pos) < DISTANCE_TO_CONNECT {
+                            Some(port_pos)
+                        } else {
+                            None
+                        }
+                    });
+                    if let Some(port_pos) = port {
+                        (port_pos, start_pos)
+                    } else {
+                        (cursor_pos, start_pos)
+                    }
+                }
             };
             draw_connection(ui.painter(), src_pos, dst_pos, connection_color);
         }
@@ -464,7 +494,15 @@ where
             };
 
             let resp = ui.allocate_rect(port_rect, sense);
-            let port_color = if resp.hovered() {
+
+            // Check if the distance between the port and the mouse is the distance to connect
+            let close_enough = if let Some(pointer_pos) = ui.ctx().pointer_hover_pos() {
+                port_rect.center().distance(pointer_pos) < DISTANCE_TO_CONNECT
+            } else {
+                false
+            };
+
+            let port_color = if close_enough {
                 Color32::WHITE
             } else {
                 port_type.data_type_color(user_state)
@@ -491,7 +529,7 @@ where
                 if origin_node != node_id {
                     // Don't allow self-loops
                     if graph.any_param_type(origin_param).unwrap() == port_type
-                        && resp.hovered()
+                        && close_enough
                         && ui.input().pointer.any_released()
                     {
                         match (param_id, origin_param) {