Clear the background outside draw function in Processing 3?

usr1000

Hello, I have a Processing Program that draws a file on canvas. The file is selected dynamically by the user.

void setup() {
  size(300, 300);
  background(0);
  stroke(255);
  noSmooth();
  textSize(15);
  text("Select a file...", 20, 30);
  selectInput("Select a file:", "fileSelected");
  frameRate(50);
}

void fileSelected(File selection) {
  if (selection == null) {
    exit(); 
  } else {
    background(0);
    // v other things...
  }
}

When I upgraded to Processing 3 I realised that the background(0) doesn't executes. I believe that none of the draw specific functions don't longer work outside draw() and setup(). Is there any way to accomplish this again? Also, I noticed that I can't pass variables to size() anymore, and I must strong type them.

Thanks!

GoToLoop

• Even for Processing 2 & 1, modifying the "canvas" outside the "Animation" Thread was never a good idea.
• Seems like Processing 3 is even more sensible to that than the older versions.
• selectInput() and its siblings are run by a separate Thread.
• Therefore we can't use any "drawing" related API there like background() for example.
• A possible approach would be to set a boolean in order to flag a File was successfully selected.
• Within draw(), keep polling that boolean.
• Once it becomes true, do the stuff that you were attempting to do from selectInput().
• And set that boolean back to false afterwards.