[gnome-control-center] wacom: Get monitor tablet has ben mapped to before calibrating

[Bastien Nocera <hadess src gnome org>]

commit 611a91b91f617c7e563751b6870b5a2c80aa5080
Author: Jason Gerecke <killertofu gmail com>
Date:   Thu Jan 12 13:02:22 2012 -0800

    wacom: Get monitor tablet has ben mapped to before calibrating
    
    More precisely, this patch checks if the tablet *could* be mapped.
    gsd_wacom_device_get_display_monitor has a side-effect of
    automatically mapping the tablet if it is necessary and possible
    to ensure that it *is* mapped.
    
    If the tablet isn't and can't be mapped, calibration is pointless.
    
    https://bugzilla.gnome.org/show_bug.cgi?id=657423

 panels/wacom/cc-wacom-page.c |   10 ++++++++++
 1 files changed, 10 insertions(+), 0 deletions(-)
---
diff --git a/panels/wacom/cc-wacom-page.c b/panels/wacom/cc-wacom-page.c
index b1fa907..0a4234a 100644
--- a/panels/wacom/cc-wacom-page.c
+++ b/panels/wacom/cc-wacom-page.c
@@ -156,6 +156,16 @@ calibrate_button_clicked_cb (GtkButton   *button,
 	GVariant *variant;
 	int *current;
 	gsize ncal;
+	gint monitor;
+
+	monitor = gsd_wacom_device_get_display_monitor (page->priv->stylus);
+	if (monitor < 0) {
+		/* The display the tablet should be mapped to could not be located.
+		 * This shouldn't happen if the EDID data is good...
+		 */
+		g_critical("Output associated with the tablet is not connected. Unable to calibrate.");
+		return;
+	}
 
 	variant = g_settings_get_value (page->priv->wacom_settings, "area");
 	current = (int *) g_variant_get_fixed_array (variant, &ncal, sizeof (gint32));