The classic Button object in Grasshopper trigger two recomputation when clicked. One is from
True, while the following is
False. However, the latter behavior is sometimes undesirable, and will clear some error messages. It is why many third-party libraries recommend a toggle instead of a button to control an immediate action.
True-only button provides a button object that only emit once when clicked.
The component is listed under Pancake tab, Logic
Or you can find it via double-clicking
When clicked as figure (a), true-only button emits true, expires all downstream components and cause them to recomputation.
When released as figure (b), the button emits false and clear all recipient component, without causing a recomputation.
Then if you change other input as figure (c), for example, changing 1 to 2, the downstream component will pull data from the button (because it is cleared), which is false.