A signal requesting an item be redrawn
This signal is emitted when an item needs to be redrawn in a GUI window. Schematic items forward requests from their child attributes.
Schematic items that change geometrically send two requests. First request for invalidaton is at the old location and the bounds for it must be calculated immediately and added to the invalid region. Second request is at the new location.
When not changing geometrically, one request may be sent. For example, changing the color will not change which pixels make up the item, so only one request is sent.
| item |
The schemaitc item requesting to be redrawn |