From 70c6777b5efcd4cb77e5415ff2c6e63a42b3b703 Mon Sep 17 00:00:00 2001
From: Dave Page <dpage@pgadmin.org>
Date: Thu, 15 Oct 2026 10:38:55 +0100
Subject: [PATCH] Fix ERD tables becoming immovable after a Shift-drag
 selection. #9890 (#10581)

---
 .../tools/erd/static/js/erd_tool/ERDCore.js   | 45 +++++++++++++-
 .../javascript/erd/erd_modifier_keys_spec.js  | 62 +++++++++++++++++++
 2 files changed, 106 insertions(+), 1 deletion(-)
 create mode 100644 web/regression/javascript/erd/erd_modifier_keys_spec.js

diff --git a/web/pgadmin/tools/erd/static/js/erd_tool/ERDCore.js b/web/pgadmin/tools/erd/static/js/erd_tool/ERDCore.js
index 117e7577b..f1d020e9f 100644
--- a/web/pgadmin/tools/erd/static/js/erd_tool/ERDCore.js
+++ b/web/pgadmin/tools/erd/static/js/erd_tool/ERDCore.js
@@ -26,6 +26,16 @@ import UniqueConstraintSchema from '../../../../../browser/server_groups/servers
 import PrimaryKeySchema from '../../../../../browser/server_groups/servers/databases/schemas/tables/constraints/index_constraint/static/js/primary_key.ui';
 import { boundingBoxFromPolygons } from '@projectstorm/geometry';
 
+/* Modifier keys as recorded by the canvas event bus, mapped to the matching
+ * flag on mouse events. */
+const MODIFIER_KEYS = {
+  shift: 'shiftKey',
+  control: 'ctrlKey',
+  alt: 'altKey',
+  meta: 'metaKey',
+};
+const MOUSE_EVENT_TYPES = ['mousedown', 'mousemove', 'mouseup', 'wheel'];
+
 export default class ERDCore {
   constructor() {
     this._cache = {};
@@ -38,7 +48,40 @@ export default class ERDCore {
   }
 
   createEngine(options) {
-    return createEngine(options);
+    let engine = createEngine(options);
+    this.releaseStaleModifierKeysOnMouseEvents(engine.getActionEventBus());
+    return engine;
+  }
+
+  /*
+   * The canvas event bus only learns that a key was released from its keyup
+   * event. If that never reaches the page (for example, Shift is released
+   * whilst focus is elsewhere), it believes Shift is still held and stays in
+   * the selecting state, where every drag draws a selection box, and tables
+   * can no longer be moved nor the canvas panned. Mouse events carry the real
+   * modifier state, so release any key the event says is no longer held
+   * before the event is handled.
+   */
+  releaseStaleModifierKeysOnMouseEvents(eventBus) {
+    const fireAction = eventBus.fireAction.bind(eventBus);
+    eventBus.fireAction = (actionEvent)=>{
+      const event = actionEvent?.event;
+      if(MOUSE_EVENT_TYPES.includes(event?.type)) {
+        for(const key of eventBus.getKeys()) {
+          if(MODIFIER_KEYS[key] && event[MODIFIER_KEYS[key]] === false) {
+            fireAction({
+              event: {
+                type: 'keyup',
+                key: key,
+                preventDefault: () => {/*This is intentional (SonarQube)*/},
+                stopPropagation: () => {/*This is intentional (SonarQube)*/},
+              },
+            });
+          }
+        }
+      }
+      fireAction(actionEvent);
+    };
   }
 
   initializeEngine() {
diff --git a/web/regression/javascript/erd/erd_modifier_keys_spec.js b/web/regression/javascript/erd/erd_modifier_keys_spec.js
new file mode 100644
index 000000000..1a5ad671c
--- /dev/null
+++ b/web/regression/javascript/erd/erd_modifier_keys_spec.js
@@ -0,0 +1,62 @@
+/////////////////////////////////////////////////////////////
+//
+// pgAdmin 4 - PostgreSQL Tools
+//
+// Copyright (C) 2013 - 2026, The pgAdmin Development Team
+// This software is released under the PostgreSQL Licence
+//
+//////////////////////////////////////////////////////////////
+import ERDCore from 'pgadmin.tools.erd/erd_tool/ERDCore';
+
+describe('ERDCore modifier keys', ()=>{
+  let engine, canvas;
+
+  const fire = (event)=>{
+    engine.getActionEventBus().fireAction({
+      event: {
+        preventDefault: ()=>{/* intentional */},
+        stopPropagation: ()=>{/* intentional */},
+        target: canvas,
+        ...event,
+      },
+    });
+  };
+  const currentState = ()=>engine.getStateMachine().getCurrentState().getOptions().name;
+
+  beforeEach(()=>{
+    engine = new ERDCore().getEngine();
+    canvas = document.createElement('div');
+    document.body.appendChild(canvas);
+    engine.setCanvas(canvas);
+  });
+
+  afterEach(()=>{
+    canvas.remove();
+  });
+
+  it('draws a selection box when dragging with Shift held', ()=>{
+    fire({type: 'keydown', key: 'Shift'});
+    fire({type: 'mousedown', clientX: 10, clientY: 10, buttons: 1, shiftKey: true});
+    expect(currentState()).toBe('selection-box');
+  });
+
+  it('pans the canvas once Shift is released, even if the keyup was missed', ()=>{
+    fire({type: 'keydown', key: 'Shift'});
+    fire({type: 'mousedown', clientX: 10, clientY: 10, buttons: 1, shiftKey: true});
+    fire({type: 'mousemove', clientX: 50, clientY: 50, buttons: 1, shiftKey: true});
+    fire({type: 'mouseup', clientX: 50, clientY: 50, buttons: 0, shiftKey: true});
+    expect(currentState()).toBe('selecting');
+
+    /* No keyup for Shift arrives, but the next mouse event says it is up */
+    fire({type: 'mousedown', clientX: 10, clientY: 10, buttons: 1, shiftKey: false});
+    expect(engine.getActionEventBus().getKeys()).not.toContain('shift');
+    expect(currentState()).toBe('drag-canvas');
+  });
+
+  it('leaves keys alone for events without modifier flags', ()=>{
+    fire({type: 'keydown', key: 'Shift'});
+    fire({type: 'mousedown', clientX: 10, clientY: 10, buttons: 1});
+    expect(engine.getActionEventBus().getKeys()).toContain('shift');
+    expect(currentState()).toBe('selection-box');
+  });
+});