fix(app): backport rendering improvements (#1580)

fluxer_app/src/features/lexical/composer/ComposerCodeIndent.ts

@@ -0,0 +1,48 @@
+// SPDX-License-Identifier: AGPL-3.0-or-later
+
+import type {ComposerTypeaheadActiveState} from '@app/features/lexical/composer/ComposerTypeaheadModifierGuard';
+import {analyzeCodeIndent} from '@app/features/lexical/composer/codeBlockIndent';
+import {
+	$captureSelectionOffsets,
+	$getComposerDisplayText,
+	$replaceComposerRange,
+	$selectComposerRange,
+} from '@app/features/lexical/composer/composerOffsets';
+import {COMMAND_PRIORITY_HIGH, KEY_TAB_COMMAND, type LexicalEditor} from 'lexical';
+
+export function registerComposerCodeIndent(
+	editor: LexicalEditor,
+	typeaheadActiveRef: ComposerTypeaheadActiveState,
+): () => void {
+	return editor.registerCommand(
+		KEY_TAB_COMMAND,
+		(event: KeyboardEvent | null) => {
+			if (typeaheadActiveRef.current) {
+				return false;
+			}
+			const offsets = $captureSelectionOffsets();
+			if (offsets == null) {
+				return false;
+			}
+			const backward = offsets.anchor > offsets.focus;
+			const start = Math.min(offsets.anchor, offsets.focus);
+			const end = Math.max(offsets.anchor, offsets.focus);
+			const plan = analyzeCodeIndent($getComposerDisplayText(), start, end, event != null && event.shiftKey === true);
+			if (plan == null) {
+				return false;
+			}
+			if (event != null) {
+				event.preventDefault();
+			}
+			for (const edit of [...plan.edits].sort((a, b) => b.start - a.start)) {
+				$replaceComposerRange(edit.start, edit.end, {kind: 'text', text: edit.text}, {trailing: false});
+			}
+			$selectComposerRange(
+				backward ? plan.selectionEnd : plan.selectionStart,
+				backward ? plan.selectionStart : plan.selectionEnd,
+			);
+			return true;
+		},
+		COMMAND_PRIORITY_HIGH,
+	);
+}