Need explanation

[trail cipher]

I already tried ai to understand this code but I still can't figure it put

[mild slate]

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[trail cipher]

public void runApp() throws Exception {
        try (var tui = TuiRunner.create()) {
            tui.run((event, runner) ->
                switch (event) {
                    case KeyEvent k when k.isChar('q') && k.hasCtrl() -> {
                        runner.quit();
                        yield true;
                    }
                    default -> false;

                },
                frame -> {
                    frame.renderWidget(Paragraph.from("Hello"), frame.area());
                }
            );
        }
    }

i get the try part and the lamba part. i am very confused in the event and switch case statements

[cold forge]

event is a variable from the lambda

[trail cipher]

yes i know that i am trying to convert this into if else statement

[cold forge]

and the switch here uses switch patternmatching which is a fairly new feature

[trail cipher]

and i also wonder why we need to return true / false in switch case

[trail cipher]

well i read the java docs and i got it somewhat but this is like next level

[cold forge]

if (event instanceof KeyEvent k && k.isChar('q') && k.hasCtrl())

[cold forge]

this is because it's using switch expressions as well and that allows returning a value from a case block resulting in the switch block returning the corresponding value

ig the lambda fof tui.run needs to return a boolean

[trail cipher]

for some reason i am more confused now

[cold forge]

This is more or less a translation of the first case

case KeyEvent k means "this has to be a KeyEvent for it to be executed and ut is assigned to a variable named k

when means "here comes an additional condition that has to be true for executing the block

https://openjdk.org/jeps/441

and the part of returning works like this:

int something = 1;

String s = switch(something) {
    case 0 -> "zero";
    case 1 -> "one";
    case 2 -> "two";
    default -> "something else";
};

[cold forge]

Can you understand that code?

[trail cipher]

we can only make lambda expression for a functional inteface/SAM and i figured out tui is a instance of TuiRunner. so it means TUIRunner is a functinal interface right?

but TuiRunner is a class

[cold forge]

No. The TuiRunner#run method has a parameter and the type of that parameter must be of a functional interface

[cold forge]

e.g. BiPredicate<Event, TuiRunner>

You are calling the run method and that method expects a parameter. That parameter is a functional interface so you can use a lambda for it.

[trail cipher]

ohh got it it its like tui.run( lambda )
i was thinking like tui.run()->lambda

[cold forge]

yes

[trail cipher]

ok its like we have

tui.run(
        (event, runner) -> {
            if (event instanceof KeyEvent k && k.hasCtrl() && k.isCharIgnoreCase('q')) {
                tui.close();
            }
        }
         ,
        frame -> {
            frame.renderWidget(Paragraph.from("Hello"), frame.area());
        }
);

we got two lambda interface in run right?
one is (event, runner)->{}
And another is (frame)->{}

[cold forge]

yes, two parameters that are using different functional interfaces

[cold forge]

Does that compile without the first lambda returning true?

[trail cipher]

nope

i don't get it what is point of returning anything there nothing seems to change anything

[cold forge]

then the functional interface probably expects returning a boolean

[cold forge]

I don't know what the run() method uses the returned value for

maybe check the documentation

[trail cipher]

yup got it

@FunctionalInterface
public interface EventHandler {

    /**
     * Handles an event.
     *
     * @param event  the event to handle
     * @param runner the TUI runner (can be used to call {@link TuiRunner#quit()})
     * @return {@code true} if the UI should be redrawn, {@code false} otherwise
     */
    boolean handle(Event event, TuiRunner runner);
}

[cold forge]

so if you return true from the first lambda it means it should redraw the UI

[trail cipher]

yup i read that but earlier i tried using false too but i don't think it changed anything

let me try once again

[cold forge]

I guess you aren't doing anything that requires redrawing in the lambda

but if you change something in the UI, it should probably redraw it

[cold forge]

and in that case, you need to return true

[trail cipher]

things make sence now it don't work if everything returns false

but i guess in earler version i made default -> true so thats why it gets updated

[cold forge]

The default is just used when nothing else matches in the switch

[trail cipher]

yes i was playing around to figure out earlier

[cold forge]

You only need to return true if you do something that requires redrawing

[trail cipher]

switch (event) {
  case KeyEvent k when k.isChar('q') && k.hasCtrl() -> {
      runner.quit();
      yield false;
  }
  case KeyEvent k when k.isKey(KeyCode.DOWN)->{
      state.selectNext(3);
      yield true;
  }case KeyEvent k when k.isKey(KeyCode.UP)->{
      state.selectPrevious();
      yield true;
  }case KeyEvent k when k.isKey(KeyCode.CHAR)->{
      textState.insert(k.character());
      yield true;
  }case KeyEvent k when k.isKey(KeyCode.BACKSPACE)->{
      textState.deleteBackward();
      yield true;
  }case KeyEvent k when k.isKey(KeyCode.DELETE)->{
      textState.deleteForward();
      yield true;
  }case KeyEvent k when k.isKey(KeyCode.LEFT)->{
      textState.moveCursorLeft();
      yield true;
  }case KeyEvent k when k.isKey(KeyCode.RIGHT)->{
      textState.moveCursorRight();
      yield true;
  }
  default -> false;

for some reason pressing BACKSPACE makes textState.insert('h') ;

i am using https://tamboui.dev/ btw

[cold forge]

What do you mean with that?

[trail cipher]

like its a InputTextWedget and so i want when i press backspace it deletes backwards but instead it just add h in my input text

would you like to try my code in your machine?

[terse pollen]

Didn't you ask like the same question one month ago? #1486760641002733821 message

[trail cipher]

man am i really that stupid. i didn't even know that

well this time i was confused because of lambda to be honest i knew the switch case statement

[trail cipher]

@terse pollen can you help me with this ?

[cold forge]

Do you have a minimal reproducer?

[trail cipher]

just run.bat https://github.com/Neo-0x01/TUI

[cold forge]

Maybe a bug in the library? idk

[trail cipher]

did you checked it?

like if you did thats like very fast

so shall i close this ?

[cold forge]

I looked at the code but I'm not running it

(and the batch file is specific to your system btw)

[trail cipher]

f i reveled my name .