Recognizing touch shapes

There is a useful tool provided by Kivy that permits us to recognize the shape of the touch that is performed. In this recipe, we will go through the foundations of using it.

Getting ready

In this recipe, we will use the Kv language for the design of the widgets, so we assume that the reader is familiar with the Kv language. Also, this recipe will use the common button and label widgets for reference.

How to do it…

Follow these steps:

1. First, in the KV file, define a button and an empty label:

   <MyW>:
       Button:
           id: button1
           pos: 0,0
           text: 'Hello'
   
       Label:
           id: label1
           pos: 50, 200
           text: ''

2. In the class of the widget in the Python code, we need to override the method on_touch_move.

3. Change the button position to the information in touch.pos.

4. Change the text in the label when a rectangular shape is present:

   import kivy
   kivy.require('1.9.0') 
   
   from kivy.app import App
   from kivy.uix.widget import Widget
   from kivy.input.shape...