From 77476a7754c03e042eb122ec2f81fa5fa2d8e618 Mon Sep 17 00:00:00 2001
From: krassowski <5832902+krassowski@users.noreply.github.com>
Date: Fri, 1 Dec 2023 12:43:46 +0000
Subject: [PATCH] Re-focus input after modifying model, keep input for 0.5s

---
 packages/outputarea/src/widget.ts  | 39 +++++++++++++++++++++++++++---
 packages/outputarea/style/base.css | 31 ++++++++++++++++++++++++
 2 files changed, 67 insertions(+), 3 deletions(-)

diff --git a/packages/outputarea/src/widget.ts b/packages/outputarea/src/widget.ts
index 8a588a57520b..76686cd24536 100644
--- a/packages/outputarea/src/widget.ts
+++ b/packages/outputarea/src/widget.ts
@@ -44,6 +44,8 @@ const OUTPUT_AREA_OUTPUT_CLASS = 'jp-OutputArea-output';
  */
 const OUTPUT_AREA_PROMPT_CLASS = 'jp-OutputArea-prompt';
 
+const OUTPUT_AREA_STDIN_HIDING_CLASS = 'jp-OutputArea-stdin-hiding';
+
 /**
  * The class name added to OutputPrompt.
  */
@@ -457,10 +459,11 @@ export class OutputArea extends Widget {
     if (this.model.length >= this.maxNumberOutputs) {
       this.maxNumberOutputs = this.model.length;
     }
-    this.layout.addWidget(panel);
-
     this._inputRequested.emit(input);
 
+    // Get the input node to ensure focus after updating the model upon user reply.
+    const inputNode = input.node.getElementsByTagName('input')[0];
+
     /**
      * Wait for the stdin to complete, add it to the model (so it persists)
      * and remove the stdin widget.
@@ -470,14 +473,37 @@ export class OutputArea extends Widget {
       if (this.model.length >= this.maxNumberOutputs) {
         this.maxNumberOutputs = this.model.length + 1;
       }
+      panel.addClass(OUTPUT_AREA_STDIN_HIDING_CLASS);
       // Use stdin as the stream so it does not get combined with stdout.
+      // Note: because it modifies DOM it may (will) shift focus away from the input node.
       this.model.add({
         output_type: 'stream',
         name: 'stdin',
         text: value + '\n'
       });
-      panel.dispose();
+      // Refocus the input node after it lost focus due to update of the model.
+      inputNode.focus();
+
+      // Keep the input in view for a little while; this (along refocusing)
+      // ensures that we can avoid the cell editor stealing the focus, and
+      // leading to user inadvertently modifying editor content when executing
+      // consecutive commands in short succession.
+      window.setTimeout(() => {
+        // Tack currently focused element to ensure that it remains on it
+        // after disposal of the panel with the old input
+        // (which modifies DOM and can lead to focus jump).
+        const focusedElement = document.activeElement;
+        // Dispose the old panel with no longer needed input box.
+        panel.dispose();
+        // Refocus the element that was focused before.
+        if (focusedElement && focusedElement instanceof HTMLElement) {
+          focusedElement.focus();
+        }
+      }, 500);
     });
+
+    // Note: the `input.value` promise must be listened to before we attach the panel
+    this.layout.addWidget(panel);
   }
 
   /**
@@ -1093,6 +1119,11 @@ export class Stdin extends Widget implements IStdin {
    * not be called directly by user code.
    */
   handleEvent(event: KeyboardEvent): void {
+    if (this._resolved) {
+      // Do not handle any more key events if the promise was resolved.
+      event.preventDefault();
+      return;
+    }
     const input = this._input;
 
     if (event.type === 'keydown') {
@@ -1112,6 +1143,7 @@ export class Stdin extends Widget implements IStdin {
           this._value += input.value;
           Stdin._historyPush(this._historyKey, input.value);
         }
+        this._resolved = true;
         this._promise.resolve(void 0);
       } else if (event.key === 'Escape') {
         // currently this gets clobbered by the documentsearch:end command at the notebook level
@@ -1227,6 +1259,7 @@ export class Stdin extends Widget implements IStdin {
   private _trans: TranslationBundle;
   private _value: string;
   private _valueCache: string;
+  private _resolved: boolean = false;
 }
 
 export namespace Stdin {
diff --git a/packages/outputarea/style/base.css b/packages/outputarea/style/base.css
index 6d59355f4f71..e566d5f2c2a9 100644
--- a/packages/outputarea/style/base.css
+++ b/packages/outputarea/style/base.css
@@ -249,6 +249,37 @@ body.lm-mod-override-cursor .jp-OutputArea-output.jp-mod-isolated::before {
   opacity: 1;
 }
 
+.jp-OutputArea-stdin-hiding:has(~ .jp-OutputArea-stdin-item) {
+  /* hide the old input immediately if a new input was attached */
+  display: none;
+}
+
+.jp-OutputArea-stdin-hiding .jp-Stdin-prompt::after {
+  content: '✓';
+  color: var(--jp-accent-color0);
+  font-weight: bold;
+  animation: jp-reveal-check 0.1s forwards;
+  font-size: 120%;
+}
+
+@keyframes jp-reveal-check {
+  0% {
+    transform: scale(0.5);
+    opacity: 0;
+  }
+
+  100% {
+    transform: scale(1);
+    opacity: 1;
+  }
+}
+
+.jp-OutputArea-stdin-hiding {
+  opacity: 0;
+  transition: opacity 0.1s ease-in;
+  transition-delay: 0.3s;
+}
+
 /*-----------------------------------------------------------------------------
 | Output Area View
 |----------------------------------------------------------------------------*/