Control flow

Flow provides several methods to control animation and tween state

Methods	Description
.play()	Play the flow
.pause()	Pause the flow
.reset()	Reset the flow state to the beginning
.seek(double duration)	Jump to a specific point in time
.restart()	Reset the state and play the flow Alias for .reset() and .play()
.stop()	Reset the state and pause the flow Alias for .reset() and .pause()
.alpha()	Get the current progress (0.0d to 1.0d)
isRunning()	Check if the flow is running
isPaused()	Check if the flow is paused

You can create a simple flow like this

import dev.deitylamb.yarrow.Yarrow;
import dev.deitylamb.yarrow.Flow;

// Graphics is any type of object that you want to use in hooks
private final Flow<Graphics> flow = Yarrow
  .<Graphics>flow(100)
  // this hook will be called every time the tick method is called
  .onTick((graphics, flow) -> {
    double opacity = flow.alpha();
    graphics.setColor(1, 1, 1, opacity);
  });

// Start transition whenever you want
flow.play(); 

public void whateverRender(Graphics gui, double delta) {
  // Tick will update the alpha of the flow
  flow.tick(gui, 10); // alpha() - 0.1
  flow.tick(gui, 50); // alpha() - 0.6

  // we can pause it
  flow.pause();

   // so progress stops at 0.6
  flow.tick(gui, 100); // alpha() - 0.6
  flow.tick(gui, 100); // alpha() - 0.6

  // resume it
  flow.play();

  flow.tick(gui, 10); // alpha() - 0.7

  // or restart it
  flow.restart();

  flow.tick(gui, 10); // alpha() - 0.1
}

Or without any Graphics

import dev.deitylamb.yarrow.Yarrow;
import dev.deitylamb.yarrow.Flow;

private final Flow<Void> flow = Yarrow.flow(100);
flow.play(); 

flow.tick(10);
flow.tick(50);

flow.alpha(); // 0.6

Simple example with Swing

// Frames per second
static final int FPS = 60;
// Time between frames
static final int DELTA = 1000 / FPS;

static final Flow<Void> flow = Yarrow.flow(2000); 

JFrame frame = new JFrame("yarrow");
frame.setSize(512, 128);

flow.play(); 
frame.add(new JPanel() {
  @Override
  protected void paintComponent(Graphics gui) {
    super.paintComponent(gui);

    flow.tick(DELTA); 
    // Get 255 alpha value for the current progress (0.0 to 1.0)
    int transparency = (int) (flow.alpha() * 255d); 

    Color color = new Color(80, 0, 255, transparency);

    gui.setColor(color);
    gui.fillRect(0, 0, getWidth(), getHeight());
  }
});

new Timer(DELTA, a -> frame.repaint()).start();

Code result

Fade-in transition

Linear interpolation

In this section, we generate a number from 0 to 255 based on the alpha progress [0, 1]

int transparency = (int) (flow.alpha() * 255d);

This looks a little clunky
Fortunately, Yarrow provides a handy method to linearly interpolate between two values based on the current alpha

It's an alias for YarrowUtils.lerp(alpha, from, to)

int transparency = (int) (flow.alpha() * 255d); 
int transparency = flow.lerp(0, 255); 

Color interpolation

There is also a shortcut method to interpolate between two colors
dev.deitylamb.yarrow.common.Color

import dev.deitylamb.yarrow.common.Color; 

Color color = flow.lerp(Color.RED, Color.BLUE);

color.red();
color.green();
color.blue();