egui::TextEdit::singleline characters appear very slowly when using a barcode scanner to input content

`ui.add(egui::TextEdit::singleline(&mut self.qr_code).desired_width(f32::INFINITY));`
When the barcode scanner inputs content into this field, the characters appear very slowly. The barcode scanner displays text at normal speed in Notepad and in text fields of programs developed with other languages.

Start by reproducing the issue with a barcode scanner in egui::TextEdit::singleline using the example code from the report, then trace the text-input handling. Done means scanner-entered characters appear at normal speed, as they do in Notepad and other applications.

Written by the indexing model from the issue text.