[Development] Moving QDesktopServices from Gui to Core?

[Juha Vuolle]

> QtNetworkauth leaves the QDesktopServices::openUrl() usage/non-usage
> at the user's discretion, and thus that currently won't force a Gui
> dependency.

(Ah shoot. Correcting myself, in the new qtnetworkauth class we do
need to call QDesktopServices::openUrl() too to forward any unhandled
URLs.)

> The concrete need for QtNetworkAuth at the moment is
> QDesktopServices::setUrlHandler() and
> QDesktopServices::unsetUrlHandler().
> There is a new (Qt 6.8) class which needs to use these *) and that
> would create a module-level Gui dependency (unless using plugins or
> somesuch).
>
> Hence I'm wondering if, as a pragmatic pre-move, moving the
> implementation of those two functions behind a private header in
> QtCore (IIUC this is Tor Arne's proposal) would be
> sensible/acceptable?
>
> *) In order to be able to use custom-scheme and https-scheme redirect_uris
>
> Cheers,
> Juha
>
> > On 6 May 2024, at 09:51, Lars Knoll via Development <development at qt-project.org> wrote:
> >
> >
> >
> > On 6 May 2024, at 09:02, Marc Mutz via Development <development at qt-project.org> wrote:
> >
> > Hi,
> >
> > Juha is currently improving the OAuth implementation in QtNetworkAuth.
> > The protocol involves launching the system browser to get an access
> > code, in turn used to get access tokens with which services can then be
> > accessed.
> >
> > OAuth therefore requires a UI to run the browser in, but not necessarily
> > a _G_UI (the system browser could be lynx). Even if a CLI tool like a
> > mail fetcher, backup program, or VPN client will eventually launch
> > Firefox or Chrome, I think it's too much to ask to link to QtGui just to
> > do the equivalent of exec xdf-open <url>.
> >
> >
> > I’d agree with that. And there’s no way to do OAuth without launching a browser during the authentication process.
> >
> >
> > I've looked at the implementation of openUrl(), and the only
> > Gui-dependency is on the platform helpers. The handler registration is
> > only using Core functionality.
> >
> > I would therefore propose to move the services code from Gui to Core
> > (QTBUG-125085), so QtNetworkAuth can access it w/o incurring a Gui
> > dependency.
> >
> > After a quick look, I can see two ways to do that:
> > - keep the platform handling code in the platform helpers, incl. Gui
> > dependency, and only move the handler registration to Core
> > - move the platform url handlers out of the platform helpers into (a
> > plugin for) Core
> >
> > The first would enable users to write their own handlers w/o Gui
> > dependency, but has the disadvantage that the code behaves differently,
> > depending on whether QtGui is loaded or not.
> >
> > The second would be more work, but with consistently better user experience.
> >
> > Is there a reason other than history for the openUrl handlers to be in
> > the platform handlers? We have XDG-code in QtCore already (mime types),
> > so we should have all the information in Core already to implement the
> > functionality, should we not?
> >
> >
> > I believe the reason for this is mainly history. Moving this to Qt Core makes sense IMO.
> >
> > I don’t think you need a separate plugin for Qt Core to implement this though. I’m a bit unsure about the windows code, but on Linux and macOS it’s simply launching ‘xdg-open’ or ‘open’. It would probably fit better to simply follow the usual pattern for Qt Core with a _platform.cpp implementation file.
> >
> > Cheers,
> > Lars
> >
> >
> >
> > Thanks,
> > Marc
> >
> > --
> > Marc Mutz <marc.mutz at qt.io> (he/his)
> > Principal Software Engineer
> >
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