core: Add CogView::cog_view_set_visible()

Set the view as the one visible inside of the viewport where the view is
attached.

core/cog-view.c

@@ -478,3 +478,28 @@ cog_view_is_visible(CogView *self)
     CogView *visible_view = cog_viewport_get_visible_view(viewport);
     return self == visible_view;
 }
+
+/**
+ * cog_view_set_visible:
+ * @self: A view.
+ *
+ * Set the view as the one visible inside of the viewport where the view is
+ * attached.
+ *
+ * Returns: True if the view succesfully set as visible in its viewport and
+ * false in any other case.
+ *
+ * Since: 0.20
+ */
+gboolean
+cog_view_set_visible(CogView *self)
+{
+    g_assert(COG_IS_VIEW(self));
+
+    g_autoptr(CogViewport) viewport = cog_view_get_viewport(self);
+    g_return_val_if_fail(viewport != NULL, false);
+
+    cog_viewport_set_visible_view(viewport, self);
+
+    return true;
+}

core/cog-view.h

@@ -58,4 +58,7 @@ CogViewport *cog_view_get_viewport(CogView *self);
 COG_API
 gboolean cog_view_is_visible(CogView *self);
 
+COG_API
+gboolean cog_view_set_visible(CogView *self);
+
 G_END_DECLS