add copy toolbar to abacus

[walter]

After calculations, results should be available to the clipboard

Also, numbers should be able to be pasted to the abacus and displayed.

[walter]

Please note that I recently pushed to git a patch to allow typing values into to set the abacus to a particular number. Needs a bit more work, but it should be useful if you want to implement 'paste'.

​http://git.sugarlabs.org/projects/abacus/repos/mainline/commits/c76e411c2c50224288f2cbe783c30e8ae0821cbd

[walter]

Please refer to #2323 for some ideas as to what would need to be done for this ticket.

[tonyforster]

So you will be able, for example, to convert a decimal number to a binary representation? What about not zeroing the abacus when you change scales as an easy alternative for these conversions? What about pasting fractions into integer abacuses? What when a number has 2 different representations on the one abacus?

[walter]

So you will be able, for example, to convert a decimal number to a binary representation?

Yes. In the version currently in git, you can type numbers (on the bar where the results are displayed) and whatever abacus you are using will display those results.

What about not zeroing the abacus when you change scales as an easy alternative for these conversions?

Do you have the abacus start with the value of whatever abacus you had previously been using?

What about pasting fractions into integer abacuses? What when a number has 2 different representations on the one abacus?

At present, if you type in a fraction on an integer abacus, you only get the whole number part. If you type a number too large to fit on an abacus, you get a somewhat random result. (I need to do some bounds checking.)

The most "efficient" representation is used when more than one is available (i.e., maximizing the use of top beads and beads towards the left).

There is currently a "bug" regarding inputing some fractions: for example, inputing 1/3 will not result in a 1/3 bead being selected, since internally I make a decimal approximation. I need to think about the best way to handle this.

[walter]

​http://git.sugarlabs.org/projects/abacus/repos/mainline/commits/fd911751574e06f9f013eb80fbecdcda1b58afa5

A variation of Shanjit's patch