IO, Handlers, State Polling

Handlers

Handlers are items that submit a callback when the specified state of an item changes.

Handlers can be activated or deactivated by showing or hiding them.

Handlers are required to be added to a handler registry.

Item Handlers

Item handlers listen for states related to a specific item.

Events:

• Activated

• Active

• Clicked

• Deactivated

• Deactivated After Edited

• Focus

• Hover

• Resize

• Toggled

• Visible

Item handlers are required to be added to a item handler registry.

Item handler registries can be bound to an item. They can be bound to multiple items to prevent having to duplicate handlers for every item.

import dearpygui.dearpygui as dpg

dpg.create_context()

def change_text(sender, app_data):
    dpg.set_value("text item", f"Mouse Button ID: {app_data}")

def visible_call(sender, app_data):
    print("I'm visible")

with dpg.item_handler_registry(tag="widget handler") as handler:
    dpg.add_item_clicked_handler(callback=change_text)
    dpg.add_item_visible_handler(callback=visible_call)

with dpg.window(width=500, height=300):
    dpg.add_text("Click me with any mouse button", tag="text item")
    dpg.add_text("Close window with arrow to change visible state printing to console", tag="text item 2")

# bind item handler registry to item
dpg.bind_item_handler_registry("text item", "widget handler")
dpg.bind_item_handler_registry("text item 2", "widget handler")

dpg.create_viewport(title='Custom Title', width=800, height=600)
dpg.setup_dearpygui()
dpg.show_viewport()
dpg.start_dearpygui()
dpg.destroy_context()

Global Handlers (IO Input)

Global handlers listen for actions not tied to a specific item:

Keys:

• Down

• Press

• Release

Mouse:

• Click

• Double Click

• Down

• Drag

• Move

• Release

• Wheel

Global handlers are required to be added to a handler registry.

Registries provide a grouping aspect to handlers allowing separation by input device. They also provide the ability to turn on and off the entire registry.

For example this can allow a mouse input registry or a keyboard input registry. Registries also give the ability to deactivate all their children handlers by simply hiding the registry.

import dearpygui.dearpygui as dpg

dpg.create_context()

def change_text(sender, app_data):
    dpg.set_value("text_item", f"Mouse Button: {app_data[0]}, Down Time: {app_data[1]} seconds")

with dpg.handler_registry():
    dpg.add_mouse_down_handler(callback=change_text)

with dpg.window(width=500, height=300):
    dpg.add_text("Press any mouse button", tag="text_item")

dpg.create_viewport(title='Custom Title', width=800, height=600)
dpg.setup_dearpygui()
dpg.show_viewport()
dpg.start_dearpygui()
dpg.destroy_context()

Polling Item State

Polling item state is accessible through get_item_state. These can be very powerful when combined with handlers as shown below.

import dearpygui.dearpygui as dpg

dpg.create_context()

def change_text(sender, app_data):
    if dpg.is_item_hovered("text item"):
        dpg.set_value("text item", f"Stop Hovering Me, Go away!!")
    else:
        dpg.set_value("text item", f"Hover Me!")

with dpg.handler_registry():
    dpg.add_mouse_move_handler(callback=change_text)

with dpg.window(width=500, height=300):
    dpg.add_text("Hover Me!", tag="text item")


dpg.create_viewport(title='Custom Title', width=800, height=600)
dpg.setup_dearpygui()
dpg.show_viewport()
dpg.start_dearpygui()
dpg.destroy_context()