Undo and Redo Button

Processing Coding Questions
1 
// Press CTRL+Z to undo, CTRL+SHIFT+Z to redo 
// We need these to know if CTRL/SHIFT are pressed
boolean controlDown = false;
boolean shiftDown = false;
 
Undo undo;
 
void setup() {
 size(500, 500);
  background(255);
  undo = new Undo(10);
}
void draw() {
  // Our two line drawing program
  if (mousePressed)
    line(mouseX, mouseY, pmouseX, pmouseY);
}
void mouseReleased() {
  // Save each line we draw to our stack of UNDOs
  undo.takeSnapshot();
}
 
void keyPressed() {
  // Remember if CTRL or SHIFT are pressed or not
  if (key == CODED) {
    if (keyCode == CONTROL)
      controlDown = true;
    if (keyCode == SHIFT)
      shiftDown = true;
    return;
  }
  // Check if we pressed CTRL+Z or CTRL+SHIFT+Z
  if (controlDown) {
    if (keyCode == 'Z') {
      if (shiftDown)
        undo.redo();
      else
        undo.undo();
    }
    return;
  }
  // Check if we pressed the S key
  if (key=='s') {
    saveFrame("image####.png");
  }
}

I found this code for Undo and Redo… But redo doesn’t seem to work and when I put them as a button, and none of them seem to work which is really confusing. If some as tried them as buttons and they both work please let me know what you did!!

Thanks

2

Your code, as posted, never sets controlDown or shiftDown back to false when they are released. That’s probably the problem.

3

can you show me what you mean if possible, this is a fairly new code to me since I was given this?

4

It’s very concerning that you do not understand code you were given.

When a key is pressed, the keyPressed() function runs once.
The value in keyCode is the name of the key pressed.
That value does not change inside keyPressed()!

If I press down the Shift key, what does keyPressed() do?
If I press down the Control key, what does keyPressed() do?
Answer: That’s right - it sets the appropriate boolean to true.

Does that change ever get reverted?!? That is, when is controlDown or shiftDown ever set back to false?
Hint: It’s never set back to false!

You might think about adding a keyReleased() function…

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5

oh Alright I will defenitly look into this code.

Thanks, Much appreciated

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