observer: Add missing return codes

Upon detecting the user error, supply an error code!

Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>

1 files changed, 4 insertions, 4 deletions

diff --git a/src/cairo-surface-observer.c b/src/cairo-surface-observer.c
index 75f2a46b..92f26240 100644
--- a/src/cairo-surface-observer.c
+++ b/src/cairo-surface-observer.c
@@ -1825,10 +1825,10 @@ cairo_surface_observer_elapsed (cairo_surface_t *abstract_surface)
     cairo_surface_observer_t *surface;
 
     if (unlikely (CAIRO_REFERENCE_COUNT_IS_INVALID (&abstract_surface->ref_count)))
-	return;
+	return -1;
 
     if (! _cairo_surface_is_observer (abstract_surface))
-	return;
+	return -1;
 
     surface = (cairo_surface_observer_t *) abstract_surface;
     return _cairo_observation_total_elapsed_ns (&surface->log);
@@ -1861,10 +1861,10 @@ cairo_device_observer_elapsed (cairo_device_t *abstract_device)
     cairo_device_observer_t *device;
 
     if (unlikely (CAIRO_REFERENCE_COUNT_IS_INVALID (&abstract_device->ref_count)))
-	return;
+	return -1;
 
     if (! _cairo_device_is_observer (abstract_device))
-	return;
+	return -1;
 
     device = (cairo_device_observer_t *) abstract_device;
     return _cairo_observation_total_elapsed_ns (&device->log);