HTML email view: Some links don't open browser

[Simon-Laux]

More specifically, links without a schema, like academy.qt.io/enrollments

Expected: Open link in system browser
Actual: Opening opens a blank page in the html viewer.

Tracking down the problem & Solution ideas

Foundation knowledge

The html email window has two parts: the ui and a sandboxed browser view with disable JS in which the html email is loaded.

Email source is loaded from the email:// scheme that is implemented in

deltachat-desktop/src/main/windows/html_email.ts

Lines 412 to 420 in ba6534b

	ses.protocol.handle('email', () => {
	return new Response(Buffer.from(html_content), {
	status: 200,
	headers: {
	'content-type': 'text/html; charset=utf-8',
	'Content-Security-Policy': allow_remote_content ? CSP_ALLOW : CSP_DENY,
	},
	})
	})

The http/s handlers are overwritten by handlers that call the http request method of DC core, if allow_remote_content is activated.

Then there is link handling:

deltachat-desktop/src/main/windows/html_email.ts

Lines 472 to 493 in ba6534b

	const openLink = (url: string) => {
	if (url.startsWith('mailto:') || isInviteLink(url)) {
	open_url(url)
	mainWindow.window?.show()
	} else {
	if (url.startsWith('http:') || url.startsWith('https:')) {
	shell.openExternal(url)
	} else {
	dialog
	.showMessageBox(window, {
	buttons: [tx('no'), tx('menu_copy_link_to_clipboard')],
	message: tx('ask_copy_unopenable_link_to_clipboard', url),
	})
	.then(({ response }) => {
	if (response == 1) {
	clipboard.writeText(url)
	}
	})
	}
	}
	}

This openLink function is called in two cases:

• sandboxedView.webContents.on( 'will-navigate', ... source
• sandboxedView.webContents.setWindowOpenHandler(details => { ... source

seems this is not enough to catch this case.
I suspect it tries to open it via the email:// scheme, so we might need to check if it is a domain that is tried to be opened instead of index.html.

concerns:

• we might need to expand the function in the future to load embedded images/media from the email in some edge cases? maybe?
• it might be too late when we get the call to the link in the email scheme handler, the user might already get a white/blank screen and we can not reject the request?
• last resort could be to modify the html to fix those <a href= links, to add https-scheme, but not sure we want that, could lead to more edge cases/bugs.

If you want or need dev tools for the email content add this to the code in html_email.ts.

sandboxedView.webContents.openDevTools()

[farooqkz]

@Simon-Laux Thank you so much for the details :)

[farooqkz]

Okay after investigating, other than Simon's findings, I can also confirm that it's not http, https, file or email protocols either.

[farooqkz]

This does not trigger either when clicking on the link: https://www.electronjs.org/docs/latest/api/web-contents#event-will-frame-navigate