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//! The window a web app's frames are asked of: the one that holds its canvas.
//!
//! A canvas can move to another window -- a Document Picture-in-Picture window
//! floats it -- and a frame asked of the page it left runs on that page's
//! schedule, which a browser pauses or slows while the page is hidden, as it is
//! while the person works in the floating window.
use wasm_bindgen::JsValue;
use web_sys::{HtmlCanvasElement, Window};
/// Makes `canvas` the one whose window frames are asked of.
pub(crate) fn follow(canvas: &HtmlCanvasElement) {
crate::thread_state::with(|state| *state.web.frame_canvas.borrow_mut() = Some(canvas.clone()));
}
/// The window the canvas is in now, or the page's before there is a canvas.
pub(crate) fn window() -> Option<Window> {
crate::thread_state::with(|state| {
state
.web
.frame_canvas
.borrow()
.as_ref()
.and_then(|canvas| canvas.owner_document())
.and_then(|document| document.default_view())
})
.or_else(web_sys::window)
}
/// Whether a frame already asked for will come to `current`: it was asked of
/// that window, and the window is still open. A frame asked of a window the
/// canvas has since left, or of a floating window since closed, never comes.
pub(crate) fn asked_of(current: &Window) -> bool {
crate::thread_state::with(|state| {
state
.web
.frame_asked_of
.borrow()
.as_ref()
.is_some_and(|asked| {
AsRef::<JsValue>::as_ref(asked) == AsRef::<JsValue>::as_ref(current)
&& !asked.closed().unwrap_or(true)
})
})
}
/// Records the window the pending frame was asked of.
pub(crate) fn note_asked(window: &Window) {
crate::thread_state::with(|state| {
*state.web.frame_asked_of.borrow_mut() = Some(window.clone());
});
}