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Minart/Tutorial/7. Canvas Settings

7. Canvas settings

Up until now, we've been declaring our canvas settings as a constant.

However, it can be sometimes desirable to change the settings at runtime, for example, to enter and leave fullscreen.

Here's a quick example on how to do that. In this example application, we will change the settings when the user presses "A", "B", "C" or "D".

Variable settings

Dependencies and imports

//> using scala "3.3.3"
//> using dep "eu.joaocosta::minart::0.6.0"

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

Settings

Let's define some settings. Some of those settings use a different resolution, while others go full screen.

val settingsA = Canvas.Settings(width = 128, height = 128, scale = Some(4), clearColor = Color(128, 255, 128))
val settingsB = Canvas.Settings(width = 640, height = 480, scale = None, clearColor = Color(128, 255, 128))
val settingsC =
  Canvas.Settings(width = 128, height = 128, scale = Some(4), fullScreen = true, clearColor = Color(128, 255, 128))
val settingsD = Canvas.Settings(width = 640, height = 480, scale = None, fullScreen = true, clearColor = Color(0, 0, 0))

Changing settings

The application logic is pretty simple: We grab the keyboard input and, based on the key that is pressed, we call canvas.changeSettings with the desired settings.

def changeSettings(canvas: Canvas, keyboardInput: KeyboardInput): Unit = {
  if (keyboardInput.keysPressed(KeyboardInput.Key.A)) canvas.changeSettings(settingsA)
  else if (keyboardInput.keysPressed(KeyboardInput.Key.B)) canvas.changeSettings(settingsB)
  else if (keyboardInput.keysPressed(KeyboardInput.Key.C)) canvas.changeSettings(settingsC)
  else if (keyboardInput.keysPressed(KeyboardInput.Key.D)) canvas.changeSettings(settingsD)
}

Reading settings

Since our settings will change, we also need to make sure we read the updated values. Those can be read by using Canvas#canvasSettings.

In this example, we'll draw a colored gradient that fills the screen, so we need to fetch the current width and height of the canvas. Since this is so common, we can actually just use the Canvas#width and Canvas#height methods.

def drawColors(canvas: Canvas): Unit = {
  for {
    x <- (0 until canvas.width)
    y <- (0 until canvas.height)
    color = Color((255 * x.toDouble / canvas.width).toInt, (255 * y.toDouble / canvas.height).toInt, 255)
  } canvas.putPixel(x, y, color)
}

Putting it all together

AppLoop
  .statelessRenderLoop((canvas: Canvas) => {
    val keyboardInput = canvas.getKeyboardInput()
    canvas.clear()
    changeSettings(canvas, keyboardInput)
    drawColors(canvas)
    canvas.redraw()
  })
  .configure(
    settingsA,
    LoopFrequency.Uncapped
  )
  .run()
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