Support Immutable Color

We are running into an issue where a static Color stored in the Colors map is being changed - so that the shared Color used across the game changes also. (i.e “BLACK” was changed to no longer be black)

While we’ve fixed the cause of this, it isn’t possible currently to make a Color object that enforces this. The r g b values are public, which means there is no easy way to subclass Color to make an “UnchangeableColor” class. There are hundreds of direct references to these public variables in the libGDX codebase.

Here’s what i’d propose:

1. Replace the public float r, g, b, a with getters and setters.
2. Create an unchangeable Color class that is only set in the constructor and use it for colors like “BLACK” and “RED” which should never be accidentally changed, and optionally for any unchangable colors that a game wants to add to the Colors map.

Thoughts?

[ClickerMonkey]

I apologize for bringing this up again, but I’ve had a similar design problem in my game engine and here’s how I solved it:

public interface ColorInterface {
  public Color mutable(); // returns mutable verstion, or this if already mutable
  public ImmutableColor immutable(); // returns an immutable version, or this if already immutable
  public boolean isMutable();
  // getters and setters which accept floats, ints, packed ints, & ColorInterface
}
public class Color implements ColorInterface {
   public float r, g, b, a;
  // the normal color class which is still used everywhere
}
public class ImmutableColor implements ColorInterface {
  // bare implementation of ColorInterface which ignores SETs. Maybe throws an exception?
}
public class Colors {
  public static final ImmutableColor WHITE = new ImmutableColor(1f, 1f, 1f);
  // ... more colors
}

I still was able to use the Color class everywhere - and also added methods to accept a ColorInterface when it made sense. In some places I had ColorInterface (like the background color of the window) because it wasn’t a place that was going to have heavy modifications to the color.

Not sure if this is of any help, but there it is!

[cjuillard]

Seems like basic getters/setters are inlined by the JIT on Android as of Gingerbread (2.3). ART I would imagine might even do this AOT.

http://stackoverflow.com/questions/4912695/what-optimizations-can-i-expect-from-dalvik-and-the-android-toolchain/4930538#4930538