Minart
0.6.2
DocsAPI
Generated with
Minart/Tutorial/4. Pointer Input

4. Pointer input

Now that we learned the basics of animation, we can start to look at more dynamic applications.

What we need now is to handle some input. Let's see how that's done with a simple example that uses the mouse position and button presses.

Pointer tracking

Dependencies and imports

As before, let's import the backend, graphics and runtime.

We also need to import the input package. We need this to read data from input devices, such as keyboard and mouse.

//> using scala "3.3.4"
//> using dep "eu.joaocosta::minart::0.6.2"

import eu.joaocosta.minart.backend.defaults.given
import eu.joaocosta.minart.graphics.*
import eu.joaocosta.minart.input.*
import eu.joaocosta.minart.runtime.*

Drawing the cursor

For this example, we will write a simple application that puts a pixel in the cursor position.

If the pointer input is pressed, the pixel is red, otherwise it is black.

First we then fetch the input data with canvas.getPointerInput(), to read the position and isPressed property.

Notice that now we are calling canvas.clear() at the beginning of each frame. This not only clears the image with the clear color, but also clears some information regarding the input, such as which keys and buttons were pressed on the previous frame.

[!NOTE] Since canvas.clear() clears some input information, it is usually recommended to store the input in a variable right before calling clear(), and then process the input.

def application(canvas: Canvas): Unit = {
  val mouse = canvas.getPointerInput()

  canvas.clear()

  val mouseColor =
    if (mouse.isPressed) Color(255, 0, 0)
    else Color(0, 0, 0)

  mouse.position.foreach(pos => canvas.putPixel(pos.x, pos.y, mouseColor))

  canvas.redraw()
}

[!NOTE] In this example, we call canvas.clear() in the beginning and canvas.redraw() at the end. This will reduce the frame latency but increase frame jitter. In some situations, you might prefer to call redraw() at the beginning of the frame, followed immediately by a clear().

Application Loop

Then we simply run our application.

Note that we now also added a clearColor to our canvas settings. This is the color that is rendered when the canvas is cleared.

val canvasSettings = Canvas.Settings(width = 128, height = 128, scale = Some(4), clearColor = Color(255, 255, 255))

AppLoop
  .statelessRenderLoop(application)
  .configure(canvasSettings, LoopFrequency.Uncapped) // As fast as possible
  .run()
Generated with