From 4862d6fa9c49d93c315fa4d179db90f33cfd30d1 Mon Sep 17 00:00:00 2001
From: John McLear <john@mclear.co.uk>
Date: Sat, 6 Feb 2021 19:56:59 +0000
Subject: [PATCH] editor: fix enter key keep line in view (#4639)

---
 src/static/js/ace2_inner.js       |  2 +-
 src/static/js/scroll.js           | 16 ++++++++++------
 src/tests/frontend/specs/enter.js | 29 ++++++++++++++++++++++++++++-
 3 files changed, 39 insertions(+), 8 deletions(-)

diff --git a/src/static/js/ace2_inner.js b/src/static/js/ace2_inner.js
index 194127c1d..e5de72f9c 100644
--- a/src/static/js/ace2_inner.js
+++ b/src/static/js/ace2_inner.js
@@ -2179,7 +2179,7 @@ function Ace2Inner() {
             isScrollableEditEvent(currentCallStack.type);
         const innerHeight = getInnerHeight();
         scroll.scrollWhenCaretIsInTheLastLineOfViewportWhenNecessary(
-            rep, isScrollableEvent, innerHeight
+            rep, isScrollableEvent, innerHeight*2
         );
       }
 
diff --git a/src/static/js/scroll.js b/src/static/js/scroll.js
index 063e55513..86d6a3344 100644
--- a/src/static/js/scroll.js
+++ b/src/static/js/scroll.js
@@ -282,7 +282,7 @@ Scroll.prototype.scrollNodeVerticallyIntoView = function (rep, innerHeight) {
   const linePosition = caretPosition.getPosition();
   if (linePosition) {
     const distanceOfTopOfViewport = linePosition.top - viewport.top;
-    const distanceOfBottomOfViewport = viewport.bottom - linePosition.bottom;
+    const distanceOfBottomOfViewport = viewport.bottom - linePosition.bottom - linePosition.height;
     const caretIsAboveOfViewport = distanceOfTopOfViewport < 0;
     const caretIsBelowOfViewport = distanceOfBottomOfViewport < 0;
     if (caretIsAboveOfViewport) {
@@ -290,11 +290,15 @@ Scroll.prototype.scrollNodeVerticallyIntoView = function (rep, innerHeight) {
         distanceOfTopOfViewport - this._getPixelsRelativeToPercentageOfViewport(innerHeight, true);
       this._scrollYPage(pixelsToScroll);
     } else if (caretIsBelowOfViewport) {
-      const pixelsToScroll = -distanceOfBottomOfViewport +
-        this._getPixelsRelativeToPercentageOfViewport(innerHeight);
-      this._scrollYPage(pixelsToScroll);
-    } else {
-      this.scrollWhenCaretIsInTheLastLineOfViewportWhenNecessary(rep, true, innerHeight);
+      // setTimeout is required here as line might not be fully rendered onto the pad
+      setTimeout(() => {
+        const outer = window.parent;
+        // scroll to the very end of the pad outer
+        outer.scrollTo(0, outer[0].innerHeight);
+      }, 150);
+      // if the above setTimeout and functionality is removed then hitting an enter
+      // key while on the last line wont be an optimal user experience
+      // Details at: https://github.com/ether/etherpad-lite/pull/4639/files
     }
   }
 };
diff --git a/src/tests/frontend/specs/enter.js b/src/tests/frontend/specs/enter.js
index 2f5a90a69..ca71d2081 100644
--- a/src/tests/frontend/specs/enter.js
+++ b/src/tests/frontend/specs/enter.js
@@ -6,7 +6,6 @@ describe('enter keystroke', function () {
     helper.newPad(cb);
     this.timeout(60000);
   });
-
   it('creates a new line & puts cursor onto a new line', function (done) {
     const inner$ = helper.padInner$;
 
@@ -28,4 +27,32 @@ describe('enter keystroke', function () {
       done();
     });
   });
+
+  it('enter is always visible after event', async function () {
+    const originalLength = helper.padInner$('div').length;
+    let $lastLine = helper.padInner$('div').last();
+
+    // simulate key presses to enter content
+    let i = 0;
+    const numberOfLines = 15;
+    let previousLineLength = originalLength;
+    while (i < numberOfLines) {
+      $lastLine = helper.padInner$('div').last();
+      $lastLine.sendkeys('{enter}');
+      await helper.waitFor(() => helper.padInner$('div').length > previousLineLength);
+      previousLineLength = helper.padInner$('div').length;
+      // check we can see the caret..
+
+      i++;
+    }
+    await helper.waitFor(() => helper.padInner$('div').length === numberOfLines + originalLength);
+
+    // is edited line fully visible?
+    const lastLine = helper.padInner$('div').last();
+    const bottomOfLastLine = lastLine.offset().top + lastLine.height();
+    const scrolledWindow = helper.padChrome$('iframe')[0];
+    const scrolledAmount = scrolledWindow.contentWindow.pageYOffset +
+        scrolledWindow.contentWindow.innerHeight;
+    await helper.waitFor(() => scrolledAmount >= bottomOfLastLine);
+  });
 });