Fixes #32819: A character representable with 1 UTF16 code unit can take up to 3 UTF8 code units

src/vs/workbench/services/textfile/electron-browser/modelBuilder.ts

@@ -73,7 +73,7 @@ class ModelLineBasedBuilder {
 		this.BOM = '';
 		this.lines = [];
 		this.currLineIndex = 0;
-		this.buff = Buffer.alloc(2 * PREALLOC_BUFFER_CHARS);
+		this.buff = Buffer.alloc(3/*any UTF16 code unit could expand to up to 3 UTF8 code units*/ * PREALLOC_BUFFER_CHARS);
 	}
 
 	public acceptLines(lines: string[]): void {

src/vs/workbench/services/textfile/test/modelBuilder.test.ts

@@ -145,4 +145,8 @@ suite('ModelBuilder', () => {
 	test('ASCII handling 1', () => {
 		testModelBuilder(['Hello world!!\nHow do you do?Züricha📚📚b']);
 	});
+
+	test('issue #32819: some special string cannot be displayed completely', () => {
+		testModelBuilder(['ＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡＡ123']);
+	});
 });