Layout UI: Moving a block around should trigger the "dirty" form flag.

[klonos]

While trying to help @bd0bd in #1574, I've noticed that if I move blocks around either within the same region in order to reorder them or to a different region, the "This form has unsaved changes." warning is not shown. Shouldn't it?

[klonos]

...same when you remove a block.

[docwilmot]

Done.

[quicksketch]

Could we use the same message both when a block is removed and when moving blocks around? The message for "Block X removed." doesn't tell me anything new. Seems like the same message should be displayed both when moving or removing (This form has unsaved changes. Click "Save layout" to make changes permanent or "Cancel" to discard changes.)

[docwilmot]

I thought this, but that was the message already there if !backdrop_is_ajax(). But agreed, changed, pushed.