From 47a9266a1f592451cf8cc1e92643fcb10b818467 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Micha=C5=82=20Krassowski?=
 <5832902+krassowski@users.noreply.github.com>
Date: Mon, 4 Mar 2024 08:49:53 +0000
Subject: [PATCH] Backport PR #15790: Prevent command shortcuts from preventing
 user input

---
 packages/application/src/lab.ts | 81 +++++++++++++++++++++++++++++++++
 1 file changed, 81 insertions(+)

diff --git a/packages/application/src/lab.ts b/packages/application/src/lab.ts
index d1e205819b67..87b284494a17 100644
--- a/packages/application/src/lab.ts
+++ b/packages/application/src/lab.ts
@@ -199,6 +199,72 @@ export class JupyterLab extends JupyterFrontEnd<ILabShell> {
     });
   }
 
+  /**
+   * Override keydown handling to prevent command shortcuts from preventing user input.
+   *
+   * This introduces a slight delay to the command invocation, but no delay to user input.
+   */
+  protected evtKeydown(event: KeyboardEvent): void {
+    // Process select keys which may call `preventDefault()` immediately
+    if (
+      ['Tab', 'ArrowDown', 'ArrowUp', 'ArrowRight', 'ArrowLeft'].includes(
+        event.key
+      )
+    ) {
+      return this.commands.processKeydownEvent(event);
+    }
+    // Process remaining events conditionally, depending on whether they would lead to text insertion
+    const causesInputPromise = Promise.race([
+      new Promise(resolve => {
+        if (!event.target) {
+          return resolve(false);
+        }
+        event.target.addEventListener(
+          'beforeinput',
+          (inputEvent: InputEvent) => {
+            switch (inputEvent.inputType) {
+              case 'historyUndo':
+              case 'historyRedo': {
+                if (
+                  inputEvent.target instanceof Element &&
+                  inputEvent.target.closest('[data-jp-undoer]')
+                ) {
+                  // Allow to use custom undo/redo bindings on `jpUndoer`s
+                  inputEvent.preventDefault();
+                  return resolve(false);
+                }
+                break;
+              }
+              case 'insertLineBreak': {
+                if (
+                  inputEvent.target instanceof Element &&
+                  inputEvent.target.closest('.jp-Cell')
+                ) {
+                  // Allow to override the default action of Shift + Enter on cells as this is used for cell execution
+                  inputEvent.preventDefault();
+                  return resolve(false);
+                }
+                break;
+              }
+            }
+            return resolve(true);
+          },
+          { once: true }
+        );
+      }),
+      new Promise(resolve => {
+        setTimeout(() => resolve(false), Private.INPUT_GUARD_TIMEOUT);
+      })
+    ]);
+    causesInputPromise
+      .then(willCauseInput => {
+        if (!willCauseInput) {
+          this.commands.processKeydownEvent(event);
+        }
+      })
+      .catch(console.warn);
+  }
+
   private _info: JupyterLab.IInfo = JupyterLab.defaultInfo;
   private _paths: JupyterFrontEnd.IPaths;
   private _allPluginsActivated = new PromiseDelegate<void>();
@@ -373,3 +439,18 @@ export namespace JupyterLab {
       | JupyterFrontEndPlugin<any, any, any>[];
   }
 }
+
+/**
+ * A namespace for module-private functionality.
+ */
+namespace Private {
+  /**
+   * The delay for invoking a command introduced by user input guard.
+   * Decreasing this value may lead to commands incorrectly triggering
+   * on user input. Increasing this value will lead to longer delay for
+   * command invocation. Note that user input is never delayed.
+   *
+   * The value represents the number in milliseconds.
+   */
+  export const INPUT_GUARD_TIMEOUT = 10;
+}