block closing the browser tab while there is unsaved text in a text box

[Mattia Rizzolo]

Several web sites spawn a pop-up blocking the closing of the current tab if I try to close the tab and there is unsaved text in some text box. I find that pretty convenient in several cases. I might not lose the text because my browser is clever and if I undo the "closing tab" action it also restores the text in the relevant text boxes, but I'd probably prefer to not do it.
To me, most of the time I accidentally close a tab is because I try to use ^W to delete a word like a do in vim and that clashes with the "close tab" shortcut; hence most of the times I close a tab with an editing ongoing is an error, and I appreciate websites stopping the action.