[Spice-devel] [spice-gtk v3 3/3] gtk-session: clipboard: x11: do not request data while on focus

[Marc-André Lureau]

Hi

On Thu, Jan 10, 2019 at 4:47 PM Victor Toso <victortoso at redhat.com> wrote:
>
> From: Victor Toso <me at victortoso.com>
>
> If SpiceGtkSession is holding the keyboard, that's huge indication
> that the client should not be requesting guest's clipboard data yet.
>
> This patch adds a check in clipboard_get() callback, to avoid such
> requests. In Linux, this only happens with X11 backend.
>
> This patch helps to handle a possible state race between who owns the
> grab between client and agent which could lead to agent clipboard
> failing or getting stuck, see:

hmm

> The way to reproduce the race might depend on guest system and
> applications but it is connected to amount of VDAGENTD_CLIPBOARD_GRAB
> sent by the agent which depends on the amount of clipboard changes in
> the guest. Simple example is on RHEL 6.10, with Gedit, select a text
> char by char; Client receives VDAGENTD_CLIPBOARD_GRAB every time a new
> char is selected instead of once when the full message is selected.

Sorry, you get a lot of clipboard-grab from the remote, but where is
the problem?

>
> v2 -> v3:
> * Split the fix in two patches while adding some info in a 3rd patch;
> * Kept the "clipboard_clear" as it was (Jakub)
> * Added a "clipboard_grab" log in clipboard_grab() function;
>
> Related: https://gitlab.freedesktop.org/spice/win32/vd_agent/issues/6
> Related: https://gitlab.freedesktop.org/spice/linux/vd_agent/issues/9
> Related: https://bugzilla.redhat.com/show_bug.cgi?id=1594876
>
> Signed-off-by: Victor Toso <victortoso at redhat.com>
> ---
>  src/spice-gtk-session.c | 15 +++++++++++++++
>  1 file changed, 15 insertions(+)
>
> diff --git a/src/spice-gtk-session.c b/src/spice-gtk-session.c
> index 85d5880..f5959f7 100644
> --- a/src/spice-gtk-session.c
> +++ b/src/spice-gtk-session.c
> @@ -763,6 +763,19 @@ static void clipboard_get(GtkClipboard *clipboard,
>
>      SPICE_DEBUG("clipboard get");
>
> +#ifdef GDK_WINDOWING_X11
> +    /* Do not request clipboard data while we are still interacting with the
> +     * Guest; Clipboard data could change shortly and this request would just
> +     * be wasteful. */

I don't think there is anything preventing another app the clipboard
data while spice-gtk has the focus. In fact, that's how clipboard
manager work afaik.

> +    if (GDK_IS_X11_DISPLAY(gdk_display_get_default()) &&
> +        spice_gtk_session_get_keyboard_has_focus(self)) {
> +        SPICE_DEBUG("clipboard get: not requesting data while holding focus");
> +        return;
> +    }
> +#endif
> +    SPICE_DEBUG("clipboard get: has-foucus=%d",
> +                spice_gtk_session_get_keyboard_has_focus(self));
> +
>      selection = get_selection_from_clipboard(s, clipboard);
>      g_return_if_fail(selection != -1);
>      g_return_if_fail(info < SPICE_N_ELEMENTS(atom2agent));
> @@ -818,6 +831,8 @@ static gboolean clipboard_grab(SpiceMainChannel *main, guint selection,
>                                 guint32* types, guint32 ntypes,
>                                 gpointer user_data)
>  {
> +    SPICE_DEBUG("clipboard_grab");
> +
>      g_return_val_if_fail(SPICE_IS_GTK_SESSION(user_data), FALSE);
>
>      SpiceGtkSession *self = user_data;
> --
> 2.20.1
>
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-- 
Marc-André Lureau