Support Cut Copy and Paste via context menus of text morphs

[cycomachead]

Now that we can select text, and use keyboard shortcuts, we need to be able to do this from a GUI.

Because:

• Many users aren't familiar with keyboard shortcuts
• Keyboard shortcuts don't work often on mobile devices, unless you have a hardward keyboard!

If there's a "selection", then "cut" and "copy" should show, otherwise, just "paste".

For future reference: https://hacks.mozilla.org/2015/09/flash-free-clipboard-for-the-web/

[jmoenig]

Yep, agreed!

[cycomachead]

So, I was taking a crack at this, and I realized I'm not sure which elements the context menu belongs to....

• CursorMorph doesn't make sense because you can't really click on the actual cursor!
• StringMorph is a good candidate, but many strings aren't editable, and when you have no text typed, you wouldn't be able to use paste. This would also probably mean TextMorph as well.
• InputSlotMorph, FrameMorph, InputFieldMorph all could make sense because they have children which accept text. But then their menus need to check if they're editable, and eventually access a CursorMorph since that's where the browser interaction lies.

Those seem to be the only 3 containers for text input, but I'm not sure...

• Also, this makes me think the clipboard handler should be a property of a StringMorph and not a CursorMorph, but I'm not sure if that really makes as much sense...We'd have to duplicate the work for TextMorph

[cycomachead]

For reference, coming to Safari (finally): https://webkit.org/blog/6017/introducing-safari-technology-preview/