eframe/web: allow customization of prevent_default behavior
#5779
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lucasmerlin
requested changes
Mar 13, 2025
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| /// [`stopPropagation`](https://developer.mozilla.org/en-US/docs/Web/API/Event/stopPropagation) | ||
| /// is called on every event. | ||
| pub should_propagate_event: Box<dyn Fn(&egui::Event) -> bool>, | ||
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| /// Whether the web event corresponding to an egui event should have `prevent_default` called | ||
| /// on it or not. | ||
| /// | ||
| /// Defaults to true. | ||
| pub should_prevent_default: Box<dyn Fn(&egui::Event) -> bool>, |
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It's a bit weird that one is negated and the other isn't. Since should_do_default or should_not_prevent_default is weird, maybe we should rename should_propagate_event to should_stop_propagation which would also be consistent with the name of the js function.
lucasmerlin
added
web
|
Preview available at https://egui-pr-preview.github.io/pr/5779-propagate-events |
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Currently eframe calls
prevent_default()for all copy / paste events on the document, making embedding an egui application in a page (e.g. an react application) hard (as all copy & paste functionality for other elements on the page is broken by this).I'm not sure what the motivation for this is, if any.
This commit / PR adds a callback (
should_prevent_default), similar toshould_propgate_event, that an egui application can use to overwrite this behavior. It defaults to returningtruefor all events, to keep the existing behavior.I call
should_prevent_defaultin every place thatshould_propagate_eventis called (which is not all places thatprevent_defaultis called!). I'm not sure for the motivation of not callingshould_propagate_eventeverywhere thatstop_propagationis called, but I kept that behavior for theshould_prevent_defaultcallback too.Please let me know if I'm missing some existing functionality that would allow me to do this, or if there's a reason that we don't want applications to be able to customize this (i.e. if there's a reason to always
prevent_defaultfor all copy / paste events on the whole document)