Prompt to save changes when clicking File > Exit

I thought I tested this, but perhaps I accidentally tested clicking
the close button instead, since instinctively/ideally, that's just
an easier way of accessing the same function.

It should also prompt before redirecting to 98.js.org.

src/menus.js

@@ -4,7 +4,7 @@
 // import { available_languages, get_iso_language_name, get_language, get_language_emoji, get_language_endonym, localize, set_language } from "./app-localization.js";
 import { show_edit_colors_window } from "./edit-colors.js";
 import { palette_formats } from "./file-format-data.js";
-import { change_url_param, choose_file_to_paste, clear, delete_selection, deselect, edit_copy, edit_cut, edit_paste, file_load_from_url, file_new, file_open, file_save, file_save_as, image_attributes, image_flip_and_rotate, image_invert_colors, image_stretch_and_skew, redo, render_history_as_gif, sanity_check_blob, save_selection_to_file, select_all, set_magnification, show_about_paint, show_custom_zoom_window, show_document_history, show_file_format_errors, show_multi_user_setup_dialog, show_news, toggle_grid, toggle_thumbnail, undo, view_bitmap } from "./functions.js";
+import { are_you_sure, change_url_param, choose_file_to_paste, clear, delete_selection, deselect, edit_copy, edit_cut, edit_paste, file_load_from_url, file_new, file_open, file_save, file_save_as, image_attributes, image_flip_and_rotate, image_invert_colors, image_stretch_and_skew, redo, render_history_as_gif, sanity_check_blob, save_selection_to_file, select_all, set_magnification, show_about_paint, show_custom_zoom_window, show_document_history, show_file_format_errors, show_multi_user_setup_dialog, show_news, toggle_grid, toggle_thumbnail, undo, view_bitmap } from "./functions.js";
 import { show_help } from "./help.js";
 import { $G, get_rgba_from_color } from "./helpers.js";
 import { show_imgur_uploader } from "./imgur.js";
@@ -225,35 +225,37 @@ const menus = {
 				"exit application", "exit paint", "close paint window",
 			],
 			action: () => {
-				// Note: For a Chrome PWA, window.close() is allowed only if there is only one history entry.
-				// I could make it try to close the window and then navigate to the official web desktop if it fails,
-				// but that would be inconsistent, as it wouldn't close the window after using File > New or File > Open.
-				// I could make it so that it uses replaceState when opening a new document (starting a new session);
-				// that would prevent you from using Alt+Left to go back to the previous document, but that may be acceptable
-				// for a desktop app experience, where the back button is already hidden.
-				// That said, if you just installed the PWA, it will have history already (even if just the New Tab page),
-				// as the tab is converted to a window, and in that case,
-				// it would be unable to close, again being inconsistent, but less so.
-				// (If on PWA install, the app could open a fresh new window and close itself, it could work from the start,
-				// but if we try to do that, we'll be back at square one, trying to close a window with history.)
-				try {
-					// API contract is containing page can override window.close()
-					// Note that e.g. (()=>{}).bind().toString() gives "function () { [native code] }"
-					// so the window.close() must not use bind() (not that that's common practice anyway)
-					const close_overridden = frameElement && window.close && !/\{\s*\[native code\]\s*\}/.test(window.close.toString());
-					if (close_overridden || window.is_electron_app) {
-						window.close();
-						return;
+				are_you_sure(() => {
+					// Note: For a Chrome PWA, window.close() is allowed only if there is only one history entry.
+					// I could make it try to close the window and then navigate to the official web desktop if it fails,
+					// but that would be inconsistent, as it wouldn't close the window after using File > New or File > Open.
+					// I could make it so that it uses replaceState when opening a new document (starting a new session);
+					// that would prevent you from using Alt+Left to go back to the previous document, but that may be acceptable
+					// for a desktop app experience, where the back button is already hidden.
+					// That said, if you just installed the PWA, it will have history already (even if just the New Tab page),
+					// as the tab is converted to a window, and in that case,
+					// it would be unable to close, again being inconsistent, but less so.
+					// (If on PWA install, the app could open a fresh new window and close itself, it could work from the start,
+					// but if we try to do that, we'll be back at square one, trying to close a window with history.)
+					try {
+						// API contract is containing page can override window.close()
+						// Note that e.g. (()=>{}).bind().toString() gives "function () { [native code] }"
+						// so the window.close() must not use bind() (not that that's common practice anyway)
+						const close_overridden = frameElement && window.close && !/\{\s*\[native code\]\s*\}/.test(window.close.toString());
+						if (close_overridden || window.is_electron_app) {
+							window.close();
+							return;
+						}
+					} catch (e) {
+						// In a cross-origin iframe, most likely
+						// @TODO: establish postMessage API
 					}
-				} catch (e) {
-					// In a cross-origin iframe, most likely
-					// @TODO: establish postMessage API
-				}
-				// In a cross-origin iframe, or same origin but without custom close(), or top level:
-				// Not all browsers support close() for closing a tab,
-				// so redirect instead. Exit to the official web desktop.
-				// @ts-ignore
-				window.location = "https://98.js.org/";
+					// In a cross-origin iframe, or same origin but without custom close(), or top level:
+					// Not all browsers support close() for closing a tab,
+					// so redirect instead. Exit to the official web desktop.
+					// @ts-ignore
+					window.location = "https://98.js.org/";
+				});
 			},
 			description: localize("Quits Paint."),
 		}