backend-rdp: report a zero physical size to compositor

The RDP-backend is reporting a non-zero physical size
value, and there are some clients that get the resolution
in pixels directly from the physical size reported. This
leads to a resolution of 25.4 PPI (or 1px/1mm), which is too
small.

But there's no need for that. The physical size is reported
on enabling the output (in the case of RDP-backend we have
no information about it before this), and the resolution is
already set in this moment.

Report a zero physical size to compositor, what makes frontend
and clients use their default values and applications become
readable.

Signed-off-by: Leandro Ribeiro <leandrohr@riseup.net>

libweston/backend-rdp/rdp.c

@@ -526,8 +526,9 @@ rdp_output_set_size(struct weston_output *base,
 	wl_list_for_each(head, &output->base.head_list, output_link) {
 		weston_head_set_monitor_strings(head, "weston", "rdp", NULL);
 
-		/* XXX: Calculate proper size. */
-		weston_head_set_physical_size(head, width, height);
+		/* This is a virtual output, so report a zero physical size.
+		 * It's better to let frontends/clients use their defaults. */
+		weston_head_set_physical_size(head, 0, 0);
 	}
 
 	wl_list_init(&output->peers);