FlxSprite.isSimpleRender() is nasty, causing implicit batch flushes!

[kamstrup]

I noticed that EVERY FlxSprite caused an implicit flush of the SpriteBatch on every draw() entirely defeating batching at all. After much chasing I discovered that the seemingly innocent FlxSprite.isSimpleRender() is a wolf in sheep's clothes.

Not only is it a boolean check that has major unexpected side effects (changing the rendering configuration!), it also assumes that calling batch.setShader(null) is a no-op if the shader already is null. This is not true. It causes a flush() no matter if you "change" it from null to null. This could be considered an issue in libgdx, but we have to deal with it.

I looked a bit at a solution, but since there is no way to pry the active shader config from the SpriteBatch, we have no sane way to tell if we need to clear the shader... Pondering this a bit, but good ideas welcome!

[kamstrup]

For the record, I would expect an isXYZ() function to be simple ad side-effect-free, and more human readable, ala:

    @Override
    public boolean isSimpleRender()
    {
        boolean simpleGeometry = ((angle == 0) || (_bakedRotation > 0)) &&
                                 (scale.x == 1) && (scale.y == 1);
        boolean noBlend = (blend == null);
        boolean noShading = ((shader == null) && (blendGL20 == null) ||
                             (FlxG.batchShader != null && !ignoreBatchShader));

        return simpleGeometry &&
               noBlend &&
               noShading;
    }

The compiler/JIT will almost certainly optimize the temporary booleans away.

[kamstrup]

Attached a pull request with my suggested fix. It has been tested on 2 of my games. Using rotating sprites and one using 1 shader (Spider Water Up! to render the water).

[ghost]

Does this bug still exist?To know if I need to look up into it or not.

[WingEraser]

kamstrup fixed for his game, but the OpenGL ES 2.0 doesn't work as before with this PR. You're welcome to look into it.