gtk: add zoom-to-fit to gtk options.

This allows to set the option on the command line, i.e. "-display
gtk,zoom-to-fit={on,off}", overriding the default chosen by qemu.
Signed-off-by: NGerd Hoffmann <kraxel@redhat.com>
Reviewed-by: NMarkus Armbruster <armbru@redhat.com>
Message-id: 20180827095620.26774-1-kraxel@redhat.com

qapi/ui.json

@@ -1022,12 +1022,20 @@
 # GTK display options.
 #
 # @grab-on-hover: Grab keyboard input on mouse hover.
+# @zoom-to-fit: Zoom guest display to fit into the host window.  When
+#               turned off the host window will be resized instead.
+#               In case the display device can notify the guest on
+#               window resizes (virtio-gpu) this will default to "on",
+#               assuming the guest will resize the display to match
+#               the window size then.  Otherwise it defaults to "off".
+#               Since 3.1
 #
 # Since: 2.12
 #
 ##
 { 'struct'  : 'DisplayGTK',
-  'data'    : { '*grab-on-hover' : 'bool' } }
+  'data'    : { '*grab-on-hover' : 'bool',
+                '*zoom-to-fit'   : 'bool'  } }
 
  ##
  # @DisplayGLMode:

ui/gtk.c

@@ -2136,6 +2136,8 @@ static GSList *gd_vc_gfx_init(GtkDisplayState *s, VirtualConsole *vc,
                               QemuConsole *con, int idx,
                               GSList *group, GtkWidget *view_menu)
 {
+    bool zoom_to_fit;
+
     vc->label = qemu_console_get_label(con);
     vc->s = s;
     vc->gfx.scale_x = 1.0;
@@ -2199,6 +2201,12 @@ static GSList *gd_vc_gfx_init(GtkDisplayState *s, VirtualConsole *vc,
     group = gd_vc_menu_init(s, vc, idx, group, view_menu);
 
     if (dpy_ui_info_supported(vc->gfx.dcl.con)) {
+        zoom_to_fit = true;
+    }
+    if (s->opts->u.gtk.has_zoom_to_fit) {
+        zoom_to_fit = s->opts->u.gtk.zoom_to_fit;
+    }
+    if (zoom_to_fit) {
         gtk_menu_item_activate(GTK_MENU_ITEM(s->zoom_fit_item));
         s->free_scale = true;
     }