Error in "Screen.AlignHorizontal" - Values 2 and 3 are switched.

[A. Leo]

There is an error in Screen.AlignHorizontal and/or documentation:
...
http://ai2.appinventor.mit.edu/reference/components/userinterface.html#Screen
...
says, that for AlignVertical these values are correct:
1 = aligned at the top, 2 = vertically centered, 3 = aligned at the bottom
1, 2, 3 from top to bottom makes sense!

For AlignHorizontal the documentation says that these values are correct:
1 = left aligned, 2 = horizontally centered, 3 = right aligned
which would make sense.

But actually AI2 implements it like this:
1 = left aligned, 2 = right aligned, 3 = horizontally centered

So, 2 and 3 are sadly switched.
I attached the file "AlignHorizontalVertical.aia", which moves a little green canvas around and shows the settings in the titlebar.

Greetings
Andreas

[Hal Abelson]

Thanks for reporting this.   I'm working on fixing it, but I need to do it in such a way as to not break existing projects.

[Scott Ferguson]

How about  just changing the documentation?

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sf

[A. Leo]

Hello Hal,

I'm glad I could help a little.

I really have a hard time finding a solution for this error. All I can think about is searching through all existing projects and changing there sourcecodes. I studied computer science myself, but I don't know a better solution like this.

Please let me know, how you'll fix it.

Thank you
Andreas

[Abraham Getzler]

@Scott +1.

A doc change is all that's needed.

ABG

[A. Leo]

Sadly I still don't found another solution besides parsing all existing source codes.
Maybe a future mandatory conversion from AI2 to AI3 sourcecodes bundled with other errors of this kind?

Just changing the documantation works for sure, but it'll also leave a inconsistency in the documentation between vertical and horizontal allignment.

:-(

Greetings
Andreas

[Scott Ferguson]

Just changing the documantation works for sure, but it'll also leave a inconsistency in the documentation between vertical and horizontal allignment.

Agreed.

A kludge may be for the developers to swap 2 and 3 in the sources so the user can continue to use 2 for center and 3 for right align.

To the user it will work as expected.

I don't know how easy that would be to do but as long as it is documented in the sources, so others know what is going on, it might work.

Alternatively, I say bite the bullet and break any apps that are using these values and publish on the forum that the bug was fixed but broke stuff.

This is a learning tool, after all. We are not controlling the space station or air traffic with it :)

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sf