The Dismissible widget is awesome but has very limited functionality which makes it not usable in many real world applications. Let's consider adding the following features (in order of priority):

1. Allow onResize() callback to get the direction in which the item was dismissed. This is needed to implement two types of functions depending on swipe direction (e.g. bookmark and delete).

2. Add an "undo" function to restore the dismissed item by moving it back to its position. This may be useful in case if user wants to undo the dismiss action.

3. Allow custom animation in the background widgets for example by adding a new callback which gets the slider's position. The animation can be a function of a slider position, like in Google Inbox (resizing the icon on the background).