Debugging a game
Yaeger provides a debugging dialog that shows information about the current
scene, and the machine it is running on. Since this dialog requires the
Game World Update to refresh itself, it gives little information on a scene that
extends StaticScene. But on a scene that extends DynamicScene it can give
insight.
To enable the debugging dialog, start you Yaeger game with the command line argument as shown in Command line arguments.
Processors and memory
When run, a Java-program allocates memory through the JVM, the Java Virtual Machine, which is part of the Java Runtime Environment (JRE). Depending on the number of Objects that make up the program, it then uses this memory. Since, during the lifecycle of a program, more and more Objects are created, you can see the total used memory increase. When some of these Objects are no longer used by the program, the memory they use gets cleared by the JVM. Hence, the total used memory periodically decreases.
If the total used memory reaches the value of total allocated memory, the program will come to a grinding halt.
Entities, suppliers and garbage
The debugger keeps track of the number of Entities that are present on the scene.
| Entity | Explanation |
|---|---|
| Dynamic Entities | Number of entities that extend DynamicEntity |
| Static Entities | Number of entities that extend StaticEntity |
| Suppliers | Number of objects that are able to supply entities to the scene. This means all instances of EntitySpawner, but also the Scene itself. |
| Garbage | Number of Entities that have been marked as garbage, by calling the remove() method. The will be removed from the Scene during the next Game World Update, which should result in a drop of total used memory |
| Key listening entities | Number of entities that implement KeyListener |
Loaded files
Image and audio files will probably make up most of Yaeger's memory usage. To minimize this memory footprint, Yaeger reuses images if possible. Meaning, for entities that use the same image file, this image file gets loaded only once. The same goes for audio files. Because Yaeger tries to reclaim the memory if such a file is no longer used, the background audio does get added to the value in the debugger. As soon as it starts playing, Yaeger loses its reference to the loaded file, and it continues playing.