Refactoring.

[sixth-3d.git] / src / main / java / eu / svjatoslav / sixth / e3d / gui / ViewRenderListener.java

diff --git a/src/main/java/eu/svjatoslav/sixth/e3d/gui/ViewRenderListener.java b/src/main/java/eu/svjatoslav/sixth/e3d/gui/ViewRenderListener.java
new file mode 100644 (file)
index 0000000..0977ef7
--- /dev/null
+++ b/src/main/java/eu/svjatoslav/sixth/e3d/gui/ViewRenderListener.java
@@ -0,0 +1,27 @@
+/*
+ * Sixth 3D engine. Copyright ©2012-2018, Svjatoslav Agejenko, svjatoslav@svjatoslav.eu
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of version 3 of the GNU Lesser General Public License
+ * or later as published by the Free Software Foundation.
+ *
+ */
+
+package eu.svjatoslav.sixth.e3d.gui;
+
+public interface ViewRenderListener {
+
+    /**
+     * Notifies that it is about time to render next frame and
+     * allows listener to do any related processing that it needs to.
+     *
+     * Each {@link ViewRenderListener} will be notified exactly once before every frame is rendered.
+     *
+     * {@link ViewRenderListener} can determine if frame repaint is actually
+     * needed from its perspective. Frame will be rendered only if at least one listener says yes.
+     *
+     * @return <code>true</code> if underlying view shall be re-rendered. If at least one of the view update listeners
+     * returns <code>true</code>, view is re-rendered.
+     */
+    boolean beforeRender(ViewContext viewContext, final int millisecondsSinceLastFrame);
+}