capsules: BUGFIX: backspace/delete would send an extra EOL char #3654
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bradjc
reviewed
Sep 5, 2023
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It would also be great if you could add this case to https://github.com/tock/tock/blob/master/tools/check_process_console.py
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I've moved the "DEL" logic to next_state() and I've modified the "deleting" test to run same checks for both types of delete sequences. I also had to modify the evaluation function of the tests because they were interpreting |
bradjc
approved these changes
Sep 7, 2023
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Pull Request Overview
Whilst working on tockloader-rs/listen-prototype I've noticed a few peculiarities with the handling of backspace & delete. To cut a very long story short - every time backspace/delete/ANSI Delete is pressed in the process-console, an additional "null"/"end of line" byte is send. Python tockloader does not have an issue with this because its terminal emulator automatically converts it into a unicode character. The issue comes when developing for tockloader-rs where there isn't (or I haven't found) a fully-functional terminal emulator. As such, all bytes are treated as-is.
This also means null is a by out-of-place. Tock sends , which in effect should just delete the last byte. For the Unicode Null this works. For run-of-the-mill null, this doesn't work, and in fact it deletes the byte behind the . I don't know why this happens, but the same effect can be had by just sending .
Moreover, delete (ascii) was handled the same as backspace, which is confusing. ANSI Escape Sequence Delete is being handled properly (minus the null shenanigans). I've just made a logical short-circuit to make the code believe it is dealing with the escape sequence rather than a del byte.
Testing Strategy
I tested this using this branch of tockloader-rs, without the fixes implemented in the aforementioned pull request.
cargo run -- listenBoard: microbit v2
TODO or Help Wanted
The short-circuit condition to make a "DEL" char be treated the same as the escape sequence is a bit wonky. It works, but it I'd like a second opinion if we can leave it as-is or maybe extract the handling of "delete" (either) into a function or something else.
Documentation Updated
/docs, or no updates are required.Formatting
make prepush.