Simple mode: click (and not drag) a block on a side pane should add it to the corresponding first empty slot

[stephanemagnenat]

Testing with a VPL1 parent and child user, they report that the lack of the click and add to empty slot behaviour is a regression for them.

[stephanemagnenat]

Testing with 11 year old kids, some do try to click on the block initially.

[stephanemagnenat]

Duplicate of #93, keeping this one as this is the original one. Here are comments from #93:

In VPL1, touching a block on the side panels adds it to an the first row having no block of the corresponding type (event/action). This is convenient because it allows to very easily add a program, and was critical in VPL1 as drag and drop was broken with some old graphic drivers on Windows.

In VPL2, this is not implemented (yet). On mobile devices, drag and drop is very natural and there is no graphic bug. The question of whether to implement this feature in VPL2 is open:

• (+) it would provide an even simple way than drag and drop to add a block.
• (+) it would be similar than in VPL1
• (-) it provides two mechanisms to make the same thing
• (-) it might prevent people to discover the drag and drop

[stephanemagnenat]

After discussion with @mbonani and @cbarraud, we decided that from a mobile-interaction point of view, this behaviour is un-natural.