zng_wgt_scroll/lazy_prop.rs
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use std::{fmt, mem};
use crate::ScrollMode;
use zng_wgt::prelude::*;
/// Lazy loading mode of a widget.
///
/// See [`lazy`] property for more details.
///
/// [`lazy`]: fn@lazy
#[derive(Clone, PartialEq)]
pub enum LazyMode {
/// Node always loaded.
Disabled,
/// Node lazy loaded.
Enabled {
/// Function that instantiates the node that replaces the widget when it is not in the init viewport.
///
/// All node methods are called on the placeholder, except the render methods, it should efficiently estimate
/// the size of the inited widget.
placeholder: WidgetFn<()>,
/// If the node is deinited when is moved out of the viewport.
///
/// If `false` the node stays loaded after the first lazy load.
///
/// If `true` the placeholder size is always used, this is to avoid the app entering a "flickering" loop
/// when the actual bounds are different causing an immediate deinit. An error is logged if the placeholder
/// size does not match.
deinit: bool,
/// The scroll directions that are considered for intersection with the viewport.
///
/// If set to [`ScrollMode::VERTICAL`] the widget is inited if it intersects on the vertical dimension only,
/// even if it is not actually in the viewport due to horizontal offset, and if `deinit` is flagged only the placeholder
/// height is enforced, the width can be different from the actual.
///
/// If set to [`ScrollMode::NONE`] this value is ignored, behaving like [`ScrollMode::PAN`].
intersect: ScrollMode,
},
}
impl LazyMode {
/// Enable lazy mode with a node that estimates the widget size.
///
/// The widget function must produce a node that is used as the layout placeholder for the actual widget content.
///
/// The widget will init when the placeholder stops being culled by render, and deinit when it starts being culled.
/// Note that in this mode the placeholder size is always used as the widget size, see the `deinit` docs in [`LazyMode::Enabled`]
/// for more details.
///
/// See [`FrameBuilder::auto_hide_rect`] for more details about render culling.
///
/// [`FrameBuilder::auto_hide_rect`]: zng_wgt::prelude::FrameBuilder::auto_hide_rect
pub fn lazy(placeholder: WidgetFn<()>) -> Self {
Self::Enabled {
placeholder,
deinit: true,
intersect: ScrollMode::PAN,
}
}
/// Like [`lazy`], but only considers the height and vertical offset to init and deinit. Like [`lazy`]
/// the placeholder height is enforced, but the width is allowed to change between placeholder and actual.
///
/// Note that if the widget is inlined the full size of the widget placeholder is enforced like [`lazy`],
/// the widget will still init and deinit considering only the vertical intersection.
///
/// [`lazy`]: Self::lazy
pub fn lazy_vertical(placeholder: WidgetFn<()>) -> Self {
Self::Enabled {
placeholder,
deinit: true,
intersect: ScrollMode::VERTICAL,
}
}
/// Like [`lazy`], but only considers the width and horizontal offset to init and deinit. Like [`lazy`]
/// the placeholder width is enforced, but the height is allowed to change between placeholder and actual.
///
/// Note that if the widget is inlined the full size of the widget placeholder is enforced like [`lazy`],
/// the widget will still init and deinit considering only the horizontal intersection.
///
/// [`lazy`]: Self::lazy
pub fn lazy_horizontal(placeholder: WidgetFn<()>) -> Self {
Self::Enabled {
placeholder,
deinit: true,
intersect: ScrollMode::HORIZONTAL,
}
}
/// Like [`lazy`] but the widget stays inited after the first, even if it is culled by render it will be present in the UI tree.
///
/// Note that this mode allows the actual size to be different from the placeholder size, so it can be used for items that
/// can't estimate their own size exactly.
///
/// This mode is only recommended for items that are "heavy" to init, but light after, otherwise the app will show degraded
/// performance after many items are inited.
///
/// [`lazy`]: Self::lazy
pub fn once(placeholder: WidgetFn<()>) -> Self {
Self::Enabled {
placeholder,
deinit: false,
intersect: ScrollMode::PAN,
}
}
/// Like [`once`], but only considers the height and vertical offset to init.
///
/// [`once`]: Self::once
pub fn once_vertical(placeholder: WidgetFn<()>) -> Self {
Self::Enabled {
placeholder,
deinit: false,
intersect: ScrollMode::VERTICAL,
}
}
/// Like [`once`], but only considers the width and horizontal offset to init.
///
/// [`once`]: Self::once
pub fn once_horizontal(placeholder: WidgetFn<()>) -> Self {
Self::Enabled {
placeholder,
deinit: false,
intersect: ScrollMode::HORIZONTAL,
}
}
/// If lazy init is mode.
pub fn is_enabled(&self) -> bool {
matches!(self, Self::Enabled { .. })
}
/// If lazy init is disabled.
pub fn is_disabled(&self) -> bool {
matches!(self, Self::Disabled)
}
/// Unwrap and correct the intersect mode.
fn unwrap_intersect(&self) -> ScrollMode {
match self {
LazyMode::Disabled => panic!("expected `LazyMode::Enabled`"),
LazyMode::Enabled { intersect, .. } => {
let m = *intersect;
if m.is_empty() {
ScrollMode::PAN
} else {
m
}
}
}
}
}
impl fmt::Debug for LazyMode {
fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
match self {
Self::Disabled => write!(f, "Disabled"),
Self::Enabled { deinit, .. } => f.debug_struct("Enabled").field("deinit", deinit).finish_non_exhaustive(),
}
}
}
/// Enables lazy init for the widget.
///
/// See [`LazyMode`] for details.
#[property(WIDGET, default(LazyMode::Disabled))]
pub fn lazy(child: impl UiNode, mode: impl IntoVar<LazyMode>) -> impl UiNode {
let mode = mode.into_var();
// max two nodes:
// * in `deinit` mode can be two [0]: placeholder, [1]: actual.
// * or can be only placeholder or only actual.
let children = vec![];
// actual child, not inited
let mut not_inited = Some(child.boxed());
let mut in_viewport = false;
match_node_list(children, move |c, op| match op {
UiNodeOp::Init => {
WIDGET.sub_var(&mode);
if let LazyMode::Enabled { placeholder, deinit, .. } = mode.get() {
if mem::take(&mut in_viewport) {
// init
if deinit {
// Keep placeholder, layout will still use it to avoid glitches when the actual layout causes a deinit,
// and the placeholder another init on a loop.
//
// This time we have the actual widget content, so the placeholder is upgraded to a full widget to
// have a place to store the layout info.
let placeholder = placeholder(()).into_widget();
c.children().push(placeholder);
}
c.children().push(not_inited.take().unwrap());
} else {
// only placeholder
let placeholder = placeholder(());
let placeholder = zng_app::widget::base::node::widget_inner(placeholder).boxed();
// just placeholder, and as the `widget_inner`, first render may init
c.children().push(placeholder);
}
} else {
// not enabled, just init actual
c.children().push(not_inited.take().unwrap());
}
}
UiNodeOp::Deinit => {
c.deinit_all();
if not_inited.is_none() {
not_inited = c.children().pop(); // pop actual
}
c.children().clear(); // drop placeholder, if any
}
UiNodeOp::Update { .. } => {
if mode.is_new() {
WIDGET.reinit();
}
}
UiNodeOp::Measure { wm, desired_size } => {
let mut size = c.with_node(0, |n| n.measure(wm));
if not_inited.is_none() && c.len() == 2 {
// is inited and can deinit, measure the actual child and validate
let lazy_size = size;
let actual_size = c.with_node(1, |n| n.measure(wm));
let mut intersect_mode = ScrollMode::empty();
let lazy_inline = c.children()[0]
.with_context(WidgetUpdateMode::Ignore, || WIDGET.bounds().measure_inline())
.flatten();
if let Some(actual_inline) = wm.inline() {
if let Some(lazy_inline) = lazy_inline {
fn validate<T: PartialEq + fmt::Debug>(actual: T, lazy: T, name: &'static str) {
if actual != lazy {
tracing::debug!(
target: "lazy",
"widget `{}` measure inline {name} `{actual:?}` not equal to lazy `{lazy:?}`",
WIDGET.id()
);
}
}
validate(actual_inline.first, lazy_inline.first, "first");
validate(actual_inline.first_wrapped, lazy_inline.first_wrapped, "first_wrapped");
validate(actual_inline.last, lazy_inline.last, "last");
validate(actual_inline.last_wrapped, lazy_inline.last_wrapped, "last_wrapped");
actual_inline.first = lazy_inline.first;
actual_inline.first_wrapped = lazy_inline.first_wrapped;
actual_inline.last = lazy_inline.last;
actual_inline.last_wrapped = lazy_inline.last_wrapped;
intersect_mode = ScrollMode::PAN;
} else {
tracing::debug!(target: "lazy", "widget `{}` measure inlined, but lazy did not inline", WIDGET.id());
}
} else {
if lazy_inline.is_some() {
tracing::debug!(target: "lazy", "widget `{}` measure did not inline, but lazy did", WIDGET.id());
}
intersect_mode = mode.with(|s| s.unwrap_intersect());
}
if intersect_mode == ScrollMode::PAN {
if lazy_size != actual_size {
tracing::debug!(
target: "lazy",
"widget `{}` measure size `{actual_size:?}` not equal to lazy size `{lazy_size:?}`",
WIDGET.id()
);
}
} else if intersect_mode == ScrollMode::VERTICAL {
if lazy_size.height != actual_size.height {
tracing::debug!(
target: "lazy",
"widget `{}` measure height `{:?}` not equal to lazy height `{:?}`",
WIDGET.id(),
actual_size.height,
lazy_size.height,
);
}
size.width = actual_size.width;
} else if intersect_mode == ScrollMode::HORIZONTAL {
if lazy_size.width != actual_size.width {
tracing::debug!(
target: "lazy",
"widget `{}` measure width `{:?}` not equal to lazy width `{:?}`",
WIDGET.id(),
actual_size.width,
lazy_size.width,
);
}
size.height = actual_size.height;
}
}
*desired_size = size;
}
UiNodeOp::Layout { wl, final_size } => {
let mut size = c.with_node(0, |n| n.layout(wl));
if not_inited.is_none() && c.len() == 2 {
// is inited and can deinit, layout the actual child and validate
let lazy_size = size;
let actual_size = c.with_node(1, |n| n.layout(wl));
let mut intersect_mode = ScrollMode::empty();
let lazy_inlined = c.children()[0]
.with_context(WidgetUpdateMode::Ignore, || WIDGET.bounds().inline().is_some())
.unwrap();
if wl.inline().is_some() {
if !lazy_inlined {
tracing::debug!(target: "lazy", "widget `{}` inlined, but lazy did not inline", WIDGET.id());
} else {
intersect_mode = ScrollMode::PAN;
}
} else {
if lazy_inlined {
tracing::debug!(target: "lazy", "widget `{}` layout did not inline, but lazy did", WIDGET.id());
}
intersect_mode = mode.with(|s| s.unwrap_intersect());
}
if intersect_mode == ScrollMode::PAN {
if lazy_size != actual_size {
tracing::debug!(
target: "lazy",
"widget `{}` layout size `{actual_size:?}` not equal to lazy size `{lazy_size:?}`",
WIDGET.id()
);
}
} else if intersect_mode == ScrollMode::VERTICAL {
if lazy_size.height != actual_size.height {
tracing::debug!(
target: "lazy",
"widget `{}` layout height `{:?}` not equal to lazy height `{:?}`",
WIDGET.id(),
actual_size.height,
lazy_size.height,
);
}
size.width = actual_size.width;
} else if intersect_mode == ScrollMode::HORIZONTAL {
if lazy_size.width != actual_size.width {
tracing::debug!(
target: "lazy",
"widget `{}` layout width `{:?}` not equal to lazy width `{:?}`",
WIDGET.id(),
actual_size.width,
lazy_size.width,
);
}
size.height = actual_size.height;
}
}
*final_size = size;
}
UiNodeOp::Render { frame } => {
c.delegated();
if not_inited.is_some() {
// not inited, verify
c.children()[0].render(frame); // update bounds
let intersect_mode = mode.with(|s| s.unwrap_intersect());
let outer_bounds = WIDGET.bounds().outer_bounds();
let viewport = frame.auto_hide_rect();
in_viewport = if intersect_mode == ScrollMode::VERTICAL {
outer_bounds.min_y() < viewport.max_y() && outer_bounds.max_y() > viewport.min_y()
} else if intersect_mode == ScrollMode::HORIZONTAL {
outer_bounds.min_x() < viewport.max_x() && outer_bounds.max_x() > viewport.min_x()
} else {
outer_bounds.intersects(&viewport)
};
if in_viewport {
// request init
WIDGET.reinit();
}
} else if c.len() == 2 {
// is inited and can deinit, check viewport on placeholder
c.children()[1].render(frame); // render + update bounds
frame.hide(|f| {
f.with_hit_tests_disabled(|f| {
// update bounds (not used but can be inspected)
c.children()[0].render(f);
});
});
let intersect_mode = mode.with(|s| s.unwrap_intersect());
let viewport = frame.auto_hide_rect();
let outer_bounds = WIDGET.bounds().outer_bounds();
in_viewport = if intersect_mode == ScrollMode::VERTICAL {
outer_bounds.min_y() < viewport.max_y() && outer_bounds.max_y() > viewport.min_y()
} else if intersect_mode == ScrollMode::HORIZONTAL {
outer_bounds.min_x() < viewport.max_x() && outer_bounds.max_x() > viewport.min_x()
} else {
outer_bounds.intersects(&viewport)
};
if !in_viewport {
// request deinit
WIDGET.reinit();
}
} else {
// is inited and cannot deinit
c.children()[0].render(frame);
}
}
UiNodeOp::RenderUpdate { update } => {
c.delegated();
if not_inited.is_none() {
// child is actual child
let last = c.children().len() - 1;
c.children()[last].render_update(update);
if last == 1 {
update.hidden(|u| {
// update bounds (not used but can be inspected)
c.children()[0].render_update(u);
});
}
} else {
// update bounds
c.children()[0].render_update(update);
}
}
_ => {}
})
}