[virt-tools-list] [virt-viewer RFC] Hide 'un-ready' displays after a short timeout

[Jonathon Jongsma]

When a user disables a display using the display configuration tools in the
guest, the window simply turns black and displays a "Waiting for display N..."
message.  If the user then resizes one of the windows, it will re-enable this
disabled window (rhbz#868970).

There is not a good way to determine for certain whether the display is
'permanently' disabled or whether it's a transient situation (e.g. during
display reconfigure, restarting the guest). This patch adds a workaround that
sets up a timeout to hide and formally disable the display after a short timeout
(currently 5 seconds).

In practice, this does significantly reduce the impact of rhbz#868970 (though
it's not a proper solution -- that would require significantly more invasive
changes, including a new agent capability). Unfortunately, this patch has a
slightly negative impact on the user experience of rebooting a guest. For
Windows guests, the impact is minor; for linux guests it's slightly larger:

When rebooting a linux guest with 2 displays, the non-primary display will
become 'un-ready' during shutdown, and the window will be hidden after 5
seconds. From the guest's point-of-view, this is like disconnecting the physical
monitor, so upon restart there will only be a single display.

When rebooting a Windows guest with 2 displays, the non-primary display will
also be hidden during shutdown.  But multiple monitors work differently in
windows guests than linux guests (e.g. multiple QXL devices vs multiple displays
per QXL device). Because of this, from the guest's point-of-view, there are
still 2 physical monitors attached. So after reboot, the second display will be
re-enabled and virt-viewer will show the second display.
---

There are some drawbacks to this workaround, so I'd appreciate some comments on
the general approach in addition to reviewing the code itself.

 src/virt-viewer-window.c | 27 +++++++++++++++++++++++++++
 1 file changed, 27 insertions(+)

diff --git a/src/virt-viewer-window.c b/src/virt-viewer-window.c
index af4d0bc..0ad6766 100644
--- a/src/virt-viewer-window.c
+++ b/src/virt-viewer-window.c
@@ -104,6 +104,7 @@ struct _VirtViewerWindowPrivate {
     gboolean auto_resize;
     gboolean fullscreen;
     gchar *subtitle;
+    guint source_delayed_hide;
 };
 
 static void
@@ -1205,6 +1206,17 @@ virt_viewer_window_set_usb_options_sensitive(VirtViewerWindow *self, gboolean se
     gtk_widget_set_visible(priv->toolbar_usb_device_selection, sensitive);
 }
 
+static gboolean
+delayed_hide_window(gpointer user_data)
+{
+    VirtViewerWindow *self = VIRT_VIEWER_WINDOW(user_data);
+
+    virt_viewer_window_hide(self);
+    self->priv->source_delayed_hide = 0;
+
+    return FALSE;
+}
+
 static void
 display_show_hint(VirtViewerDisplay *display,
                   GParamSpec *pspec G_GNUC_UNUSED,
@@ -1219,6 +1231,21 @@ display_show_hint(VirtViewerDisplay *display,
     gtk_widget_set_sensitive(GTK_WIDGET(gtk_builder_get_object(self->priv->builder, "menu-send")), hint);
     gtk_widget_set_sensitive(GTK_WIDGET(gtk_builder_get_object(self->priv->builder, "menu-file-screenshot")), hint);
     gtk_widget_set_sensitive(self->priv->toolbar_send_key, hint);
+
+    /* schedule the window to be hidden after a short timeout when it become
+     * 'un-ready', e.g. when a display is disabled via the guest's display
+     * configuration tools */
+    if (!hint) {
+        if (!self->priv->source_delayed_hide) {
+            self->priv->source_delayed_hide = g_timeout_add_seconds(5, delayed_hide_window, self);
+        }
+    } else {
+        if (self->priv->source_delayed_hide) {
+            g_source_remove(self->priv->source_delayed_hide);
+            self->priv->source_delayed_hide = 0;
+        }
+    }
+
 }
 static gboolean
 window_key_pressed (GtkWidget *widget G_GNUC_UNUSED,
-- 
1.8.3.1