Test the effect of DECGRA on Background Select

[j4james]

This test demonstrates how the DECGRA dimensions determine the extent of the area that is filled by the Background Select functionality. It also shows how both the Background Select parameter and the DECGRA extent have an influence on which pixels are rendered as transparent.

This is basically an attempt to cover all the weird edge cases we discussed in issue #5. If I've interpreted everything correctly, I'd expect the output to look like this:

[j4james]

Btw, if the output on the VT340 doesn't look like the screenshot above, please let me know before merging if possible. That way I can try and fix it before you do the screen capture, so you're not wasting your time on something that's going to have to be replaced.

[hackerb9]

Btw, if the output on the VT340 doesn't look like the screenshot above, please let me know before merging if possible. That way I can try and fix it before you do the screen capture, so you're not wasting your time on something that's going to have to be replaced.

It's actually easier for me to merge it before doing the screen capture, if that's alright with you.

[hackerb9]

Almost...

[j4james]

It's actually easier for me to merge it before doing the screen capture, if that's alright with you.

Not a problem. And this looks like an easy fix. I've just misunderstood how default values are interpreted in DECGRA. I thought they default to the max value (which is what would happen if there is just one DECGRA), but when you've got more than one, a default value in the second one will inherit the value from the first one (assuming that wasn't also default).

[hackerb9]

Works. Interesting that DECGRA keeps previous value.