Events

Custom events can be added to guizero widgets to call functions when the user takes the following actions:

  • when clicked - when_clicked
  • when double clicked - when_double_clicked
  • when the left mouse button is pressed - when_left_button_pressed
  • when the left mouse button is released - when_left_button_released
  • when the right mouse button is pressed - when_right_button_pressed
  • when the right mouse button is released - when_right_button_released
  • when a key is pressed - when_key_pressed
  • when a key is released - when_key_released
  • when the mouse enters a widget - when_mouse_enters
  • when the mouse leaves a widget - when_mouse_leaves
  • when the mouse is dragged across a widget - when_mouse_dragged
  • when the widget is resized - when_resized

Events are set by assigning them to a function:

def do_this():
    print("The widget was clicked")

widget.when_clicked = do_this

Event Data

The function which is called can also accept a parameter and will be passed data about the event which occurred.

The event data returned has:

  • widget - the guizero widget which raised the event
  • tk_event - the tkinter event object
  • key - the key which raised the event
  • x - the mouse's x position relative to the widget when the event occurred
  • y - the mouse's y position relative to the widget when the event occurred
  • display_x - the mouse's x position on the display when the event occurred
  • display_y - the mouse's y position on the display when the event occurred
  • width - the width of the widget.
  • height - the height of the widget.
  • keycode - the keycode of the key which raised the event.

Note: only data relevant to the event will be returned. e.g. key is only returned for when_key_# events and width and height are only returned for when_resized events.

def clicked(event_data):
    print("widget clicked = ", event_data.widget)
    print("mouse position = ", event_data.x, ".", event_data.y)

widget.when_clicked = clicked

Example

Highlight a text box widget by changing its background color (bg) when the mouse is hovering over it.

from guizero import App, TextBox

def highlight():
    text_box.bg = "lightblue"

def lowlight():
    text_box.bg = "white"

app = App()
text_box = TextBox(app)

# When the mouse enters the TextBox
text_box.when_mouse_enters = highlight
# When the mouse leaves the TextBox
text_box.when_mouse_leaves = lowlight

app.display()