GL gl = drawable.getGL();
if(drawingMode == DrawingMode.ALPHA_BLEND) {
if(isGlExtBlendSubtractSupported) {
gl.glBlendEquation(GL.GL_FUNC_ADD);
}
gl.glBlendFunc(GL.GL_SRC_ALPHA, GL.GL_ONE_MINUS_SRC_ALPHA);
} else if(drawingMode == DrawingMode.ADD) {
if(isGlExtBlendSubtractSupported) {
gl.glBlendEquation(GL.GL_FUNC_ADD);
}
gl.glBlendFunc(GL.GL_ONE, GL.GL_ONE);