High DPI rendering on JVM

[jaakkonakaza]

Graphics have to be scaled by the device's pixel ratio¹ while rendering for native resolution. The image then has to be scaled back down when showing in the Swing window to be sized properly².

Code for getting the DPR¹:

import java.awt.GraphicsEnvironment

GraphicsEnvironment
  .getLocalGraphicsEnvironment
  .getDefaultScreenDevice
  .getDefaultConfiguration
  .getDefaultTransform
  .getScaleX

Code for Swing rendering² (example from O1Library/gui/viewimpl/ViewComponent):

  final override def paintComponent(myGraphics: Graphics2D): Unit =
    for image <- latestComputed.pic.flatMap( _.toImage ) do

      val xform = AffineTransform.getScaleInstance(.5, .5)
      myGraphics.setRenderingHint(RenderingHints.KEY_INTERPOLATION, RenderingHints.VALUE_INTERPOLATION_BILINEAR)
      myGraphics.drawImage(image, xform, null)