Pagination in show images misbehaves with PgUp/PgDown

[pupssman]

What to do:

• open perspective
• say show images
• see pagination activate
• press PgUp/PgDown
• observe error messages.

Example output:

perspective>show images
Results contain 43 entries. Showing first 20 entries.
Press Space, Enter or n to show next page, p or w to show previous page, g to show first page, G to show last page, a number key to show specific page and q to type next command.
Showing page 1 of 3
....
├────────────────────────────────────────────┼────────────────────────────────────────────┼────────────────────────────────────────────┼───────────────────────────────────────────┤
│ Skeleton 1                                 │ <snip> │ saved                                      │ 5 months ago                              │
│                                            │ <snip>          │                                            │                                           │
│                                            │ <snip>                                  │                                            │                                           │
├────────────────────────────────────────────┼────────────────────────────────────────────┼────────────────────────────────────────────┼───────────────────────────────────────────┤
│ Ubuntu 08.04 hardy (updated 2014-09-19)    │ <snip> │ saved                                      │ 2 years ago                               │
│                                            │ <snip>          │                                            │                                           │
│                                            │ <snip>                                  │                                            │                                           │
└────────────────────────────────────────────┴────────────────────────────────────────────┴────────────────────────────────────────────┴───────────────────────────────────────────┘

Wrong page number: 6. Should be one of 1..3.
Wrong page number: 5. Should be one of 1..3.
Wrong page number: 6. Should be one of 1..3.
Wrong page number: 5. Should be one of 1..3.
Wrong page number: 6. Should be one of 1..3.
Wrong page number: 5. Should be one of 1..3.
Wrong page number: 6. Should be one of 1..3.
Wrong page number: 5. Should be one of 1..3.

Also, pagination notice is gone off-the-screen due to line wrap of the output.

I am running latest (of now) perspective docker container from Ubuntu.
Terminal dims are

pupssman@zeppelin:~ $ tput cols
118
pupssman@zeppelin:~ $ tput lines
103
pupssman@zeppelin:~ $ 

[vania-pooh]

@pupssman will test PgUp\PgDn soon. You may want to modify the following settings to fix width issue:

perspective> set table_width = 100 # By default it's 180 columns, you can set something about 100
perspective> set page_size = 5 # This is about page size

[pupssman]

Would be super-tool for perspective to automatically detect shell properties

[vania-pooh]

@pupssman haven't already implemented this because of http://stackoverflow.com/questions/1286461/can-i-find-the-console-width-with-java Seems that JLine does not work reliably on all platforms. And you can also save these settings to RC file and forget about this issue.

[vania-pooh]

@pupssman any idea how to check that PgDn is presed in Java? :) Can't find the way how to do this.

[pupssman]

Ehm, it looks like it is already being detected but interpreted wrong.
Did you by any chance manage to reproduce the issue?

[vania-pooh]

@pupssman yes, same thing on my Mac. For some reason PgDn key is being interpreted just as I'm pressing numeric key = 6. In your example you have only 3 pages that's why it complains about wrong page number. If you have more than 6 pages it switches to page 5 or 6 depending on key.

[vania-pooh]

I will postpone this for the future because after deep investigation it seems that handling PageDown is not a trivial task because in Bash it's represented as an Ansi escape sequence (i.e. 3 or 4 chars). Right now we expect only one char so the working solution to handle PageDown is like that (it even requires Executors!!):

    static <T> Optional<T> routeByKey(ConsoleReader consoleReader, Map<Predicate<String>, Function<String, T>> routes, Consumer<String> onInvalidKey, Consumer<Exception> onException) {
        boolean needShutdown = false;
        try {
            if (consoleReader == null) {
                consoleReader = new ConsoleReader();
                needShutdown = true;
            }

            //Trying to read one character first
            String key = String.valueOf((char) consoleReader.readCharacter());
            for (Predicate<String> keyPredicate : routes.keySet()) {
                if (keyPredicate.test(key)) {
                    return Optional.ofNullable(routes.get(keyPredicate).apply(key));
                }
            }

            //Ansi escape sequences like PageUp or PageDown
            final StringBuilder stringBuilder = new StringBuilder(key);
            final ConsoleReader cr = consoleReader;
            ExecutorService executorService = Executors.newSingleThreadExecutor();
            Runnable task = () -> {
                while (true) {
                    try {
                        NonBlockingInputStream inputStream = (NonBlockingInputStream) cr.getInput();
                        int code = inputStream.read(5);
                        if (code < 0) {
                            break;
                        }
                        stringBuilder.append((char) code);
                    } catch (IOException ignored) {
                    }
                }
            };
            executorService.submit(task);
            executorService.awaitTermination(50, TimeUnit.MILLISECONDS);
            executorService.shutdown();
            String anotherKey = stringBuilder.toString();
            for (Predicate<String> keyPredicate : routes.keySet()) {
                if (keyPredicate.test(anotherKey)) {
                    return Optional.ofNullable(routes.get(keyPredicate).apply(anotherKey));
                }
            }

            //No valid key found
            if (onInvalidKey != null) {
                onInvalidKey.accept(anotherKey);
            }
            return Optional.empty();
        } catch (Exception e) {
            if (onException != null) {
                onException.accept(e);
            }
            return Optional.empty();
        } finally {
            if (consoleReader != null && needShutdown) {
                consoleReader.shutdown();
            }
        }
    }

The PageDown key can be coded like:

    public static final String PAGE_DOWN = new String(new char[]{
            (char) 27,
            (char) 91,
            (char) 54,
            (char) 126
    });

I implemented all this stuff and even added a test but it only works for the first page down press. Then something internal in ConsoleReader prevents next key press to work (probably some colored output processing logic).

[pupssman]

Wow, weird.