rectangles: start on helper to generate rectangle data

This is meant to be used by marks visualizer to show rectangles.

lib/util/rectangles.h

@@ -0,0 +1,43 @@
+/* rectangles.h
+ *
+ * Copyright 2018 Christian Hergert <chergert@redhat.com>
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ *
+ * SPDX-License-Identifier: GPL-3.0-or-later
+ */
+
+#pragma once
+
+#include <gtk/gtk.h>
+
+G_BEGIN_DECLS
+
+typedef struct _Rectangles Rectangles;
+
+Rectangles *rectangles_new          (gint64       begin_time,
+                                    gint64       end_time);
+void        rectangles_free         (Rectangles  *self);
+void        rectangles_draw         (Rectangles  *self,
+                                     GtkWidget   *widget,
+                                     cairo_t     *cr);
+void        rectangles_add          (Rectangles  *self,
+                                     gint64       begin_time,
+                                     gint64       end_time,
+                                     const gchar *name,
+                                     const gchar *message);
+void        rectangles_set_end_time (Rectangles  *self,
+                                     gint64       end_time);
+
+G_END_DECLS