From c9f47508e3a3a0e845e0fa27e912633eed67a8c9 Mon Sep 17 00:00:00 2001
From: Joen A <1204802+jasmussen@users.noreply.github.com>
Date: Wed, 28 Jun 2023 12:46:26 +0200
Subject: [PATCH] Editor initrial appender: Zero out margins in constrained
 layouts. (#52026)

---
 .../components/default-block-appender/content.scss    | 11 +++++++++++
 1 file changed, 11 insertions(+)

diff --git a/packages/block-editor/src/components/default-block-appender/content.scss b/packages/block-editor/src/components/default-block-appender/content.scss
index 9eecf9a7e007a..48aac077096c2 100644
--- a/packages/block-editor/src/components/default-block-appender/content.scss
+++ b/packages/block-editor/src/components/default-block-appender/content.scss
@@ -26,6 +26,17 @@
 		opacity: 0.62;
 	}
 
+	// In "constrained" layout containers, the first and last paragraphs have their margins zeroed out.
+	// In the case of this appender, it needs to apply those same rules to avoid layout shifts.
+	// Such shifts happen when the bottom margin of the Title block has been set to less than the default 1em margin of paragraphs.
+	:where(body .is-layout-constrained) & {
+		> :first-child:first-child {
+			margin-block-start: 0;
+		}
+
+		// Since this particular appender will only ever appear on an entirely empty document, we don't account for last-child.
+	}
+
 	// Dropzone.
 	.components-drop-zone__content-icon {
 		display: none;