fix(helpers): scroll the page the minimal distance in the scrollIntoViewIfNeeded fallback

When only the page itself can reveal the caret line (the editor is
half-visible in a small viewport), the fallback used the default
block: 'start' and the page jumped like PageDown on every Enter. Use
block: 'nearest' so it scrolls one line at a time, like a textarea.

Reported by Ralf Pichler (Uniquare, Jodit OEM)

Author: eric-mallac

CHANGELOG.md

@@ -9,6 +9,12 @@
 > - :house: [Internal]
 > - :nail_care: [Polish]
 
+## 4.13.21
+
+#### :bug: Bug Fix
+
+- **Helpers**: when the caret line can only be revealed by scrolling the page itself (e.g. the editor is half-visible in a small viewport), `scrollIntoViewIfNeeded` fell back to `scrollIntoView()` with the default `block: 'start'` — the element was aligned to the viewport top and the page jumped as if PageDown was pressed on every Enter. The fallback now uses `block: 'nearest'` and scrolls the minimal distance, one line at a time, like a native textarea. Reported by Ralf Pichler (Uniquare, Jodit OEM).
+
 ## 4.13.20
 
 #### :bug: Bug Fix

src/core/helpers/utils/scroll-into-view.test.js

@@ -109,4 +109,38 @@ describe('Helper inView', () => {
 			}
 		});
 	});
+
+	// When only the page itself can reveal the element, the fallback must
+	// scroll the minimal distance (block: nearest) — the default aligns the
+	// element to the viewport top and the page jumps like PageDown was
+	// pressed while typing at the bottom edge of a half-visible editor
+	describe('Page-level fallback', () => {
+		it('Should call scrollIntoView with block: nearest', () => {
+			const { scrollIntoViewIfNeeded } = Jodit.modules.Helpers;
+
+			// a non-scrollable box below the viewport: the container branch
+			// cannot help, only the page can be scrolled
+			const box = document.createElement('div');
+			box.style.cssText = `position:absolute;left:0;top:${
+				document.documentElement.clientHeight + 500
+			}px;width:100px;height:100px;`;
+
+			const child = document.createElement('p');
+			child.style.cssText = 'height:100px;margin:0;';
+			box.appendChild(child);
+			document.body.appendChild(box);
+
+			let options;
+			child.scrollIntoView = opt => {
+				options = opt;
+			};
+
+			try {
+				scrollIntoViewIfNeeded(child, box, document);
+				expect(options).deep.equals({ block: 'nearest' });
+			} finally {
+				box.remove();
+			}
+		});
+	});
 });

src/core/helpers/utils/scroll-into-view.ts

@@ -93,7 +93,11 @@ export function scrollIntoViewIfNeeded(
 		}
 
 		if (!inView(elm, root, doc)) {
-			elm.scrollIntoView();
+			// `block: 'nearest'` scrolls the page the minimal distance (one
+			// line while typing), while the default `block: 'start'` aligns
+			// the element to the viewport top and the page jumps like
+			// PageDown was pressed
+			elm.scrollIntoView({ block: 'nearest' });
 		}
 	}
 }