Basic Widget events correspond to touches on the screen. However, the concept of touch in Kivy is broader than might be intuitively assumed. It includes mouse events, finger touches, and magic pen touches. For the sake of simplicity, we will often assume in this chapter that we are using a mouse but it doesn't really change if we were to use a touch screen (and the finger or magic pen instead). The following are the three basic Widget events:
on_touch_down: When a new touch starts, for example, the action of clicking a button of the mouse or touching the screen.on_touch_move: When the touch is moved, for example, dragging the mouse or sliding the finger over the screen.on_touch_up: When the touch ends, for example, releasing the mouse button or lifting a finger from the screen.
Notice that on_touch_down takes place each time before
on_touch_move, and on_touch_up happens; the bullet list order reflects the necessary execution order. Finally, on_touch_move...
