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Fix flickering (#9012)

Browse source 
See https://zed.dev/channel/gpui-536

Fixes https://github.com/zed-industries/zed/issues/9010
Fixes https://github.com/zed-industries/zed/issues/8883
Fixes https://github.com/zed-industries/zed/issues/8640
Fixes https://github.com/zed-industries/zed/issues/8598
Fixes https://github.com/zed-industries/zed/issues/8579
Fixes https://github.com/zed-industries/zed/issues/8363
Fixes https://github.com/zed-industries/zed/issues/8207


### Problem

After transitioning Zed to GPUI 2, we started noticing that interacting
with the mouse on many UI elements would lead to a pretty annoying
flicker. The main issue with the old approach was that hover state was
calculated based on the previous frame. That is, when computing whether
a given element was hovered in the current frame, we would use
information about the same element in the previous frame.

However, inspecting the previous frame tells us very little about what
should be hovered in the current frame, as elements in the current frame
may have changed significantly.

### Solution

This pull request's main contribution is the introduction of a new
`after_layout` phase when redrawing the window. The key idea is that
we'll give every element a chance to register a hitbox (see
`ElementContext::insert_hitbox`) before painting anything. Then, during
the `paint` phase, elements can determine whether they're the topmost
and draw their hover state accordingly.

We are also removing the ability to give an arbitrary z-index to
elements. Instead, we will follow the much simpler painter's algorithm.
That is, an element that gets painted after will be drawn on top of an
element that got painted earlier. Elements can still escape their
current "stacking context" by using the new `ElementContext::defer_draw`
method (see `Overlay` for an example). Elements drawn using this method
will still be logically considered as being children of their original
parent (for keybinding, focus and cache invalidation purposes) but their
layout and paint passes will be deferred until the currently-drawn
element is done.

With these changes we also reworked geometry batching within the
`Scene`. The new approach uses an AABB tree to determine geometry
occlusion, which allows the GPU to render non-overlapping geometry in
parallel.

### Performance

Performance is slightly better than on `main` even though this new
approach is more correct and we're maintaining an extra data structure
(the AABB tree).


![before_after](https://github.com/zed-industries/zed/assets/482957/c8120b07-1dbd-4776-834a-d040e569a71e)

Release Notes:

- Fixed a bug that was causing popovers to flicker.

---------

Co-authored-by: Nathan Sobo <nathan@zed.dev>
Co-authored-by: Thorsten <thorsten@zed.dev>
This commit is contained in:
Antonio Scandurra 2024-03-11 10:45:57 +01:00 • committed by GitHub
parent 9afd78b35e
commit 4700d33728
No known key found for this signature in database
GPG key ID: B5690EEEBB952194
74 changed files with 6434 additions and 6301 deletions
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76
crates/gpui/src/elements/list.rs
View file

@ -8,11 +8,12 @@
use crate::{
point, px, size, AnyElement, AvailableSpace, Bounds, ContentMask, DispatchPhase, Edges,
Element, ElementContext, IntoElement, Pixels, Point, ScrollWheelEvent, Size, Style,
Element, ElementContext, HitboxId, IntoElement, Pixels, Point, ScrollWheelEvent, Size, Style,
StyleRefinement, Styled, WindowContext,
};
use collections::VecDeque;
use refineable::Refineable as _;
use smallvec::SmallVec;
use std::{cell::RefCell, ops::Range, rc::Rc};
use sum_tree::{Bias, SumTree};
use taffy::style::Overflow;
@ -96,6 +97,13 @@ struct LayoutItemsResponse {
item_elements: VecDeque<AnyElement>,
}
/// Frame state used by the [List] element.
#[derive(Default)]
pub struct ListFrameState {
scroll_top: ListOffset,
items: SmallVec<[AnyElement; 32]>,
}
#[derive(Clone)]
enum ListItem {
Unrendered,
@ -302,7 +310,6 @@ impl StateInner {
height: Pixels,
delta: Point<Pixels>,
cx: &mut WindowContext,
padding: Edges<Pixels>,
) {
// Drop scroll events after a reset, since we can't calculate
// the new logical scroll top without the item heights
@ -310,6 +317,7 @@ impl StateInner {
return;
}
let padding = self.last_padding.unwrap_or_default();
let scroll_max =
(self.items.summary().height + padding.top + padding.bottom - height).max(px(0.));
let new_scroll_top = (self.scroll_top(scroll_top) - delta.y)
@ -516,13 +524,13 @@ pub struct ListOffset {
}
impl Element for List {
type State = ();
type BeforeLayout = ListFrameState;
type AfterLayout = HitboxId;
fn request_layout(
fn before_layout(
&mut self,
_state: Option<Self::State>,
cx: &mut crate::ElementContext,
) -> (crate::LayoutId, Self::State) {
) -> (crate::LayoutId, Self::BeforeLayout) {
let layout_id = match self.sizing_behavior {
ListSizingBehavior::Infer => {
let mut style = Style::default();
@ -580,15 +588,15 @@ impl Element for List {
})
}
};
(layout_id, ())
(layout_id, ListFrameState::default())
}
fn paint(
fn after_layout(
&mut self,
bounds: Bounds<crate::Pixels>,
_state: &mut Self::State,
cx: &mut crate::ElementContext,
) {
bounds: Bounds<Pixels>,
before_layout: &mut Self::BeforeLayout,
cx: &mut ElementContext,
) -> HitboxId {
let state = &mut *self.state.0.borrow_mut();
state.reset = false;
@ -615,12 +623,11 @@ impl Element for List {
cx.with_content_mask(Some(ContentMask { bounds }), |cx| {
let mut item_origin = bounds.origin + Point::new(px(0.), padding.top);
item_origin.y -= layout_response.scroll_top.offset_in_item;
for item_element in &mut layout_response.item_elements {
let item_height = item_element
.measure(layout_response.available_item_space, cx)
.height;
item_element.draw(item_origin, layout_response.available_item_space, cx);
item_origin.y += item_height;
for mut item_element in layout_response.item_elements {
let item_size = item_element.measure(layout_response.available_item_space, cx);
item_element.layout(item_origin, layout_response.available_item_space, cx);
before_layout.items.push(item_element);
item_origin.y += item_size.height;
}
});
}
@ -628,20 +635,33 @@ impl Element for List {
state.last_layout_bounds = Some(bounds);
state.last_padding = Some(padding);
cx.insert_hitbox(bounds, false).id
}
fn paint(
&mut self,
bounds: Bounds<crate::Pixels>,
before_layout: &mut Self::BeforeLayout,
hitbox_id: &mut HitboxId,
cx: &mut crate::ElementContext,
) {
cx.with_content_mask(Some(ContentMask { bounds }), |cx| {
for item in &mut before_layout.items {
item.paint(cx);
}
});
let list_state = self.state.clone();
let height = bounds.size.height;
let scroll_top = before_layout.scroll_top;
let hitbox_id = *hitbox_id;
cx.on_mouse_event(move |event: &ScrollWheelEvent, phase, cx| {
if phase == DispatchPhase::Bubble
&& bounds.contains(&event.position)
&& cx.was_top_layer(&event.position, cx.stacking_order())
{
if phase == DispatchPhase::Bubble && hitbox_id.is_hovered(cx) {
list_state.0.borrow_mut().scroll(
&layout_response.scroll_top,
&scroll_top,
height,
event.delta.pixel_delta(px(20.)),
cx,
padding,
)
}
});
@ -651,10 +671,6 @@ impl Element for List {
impl IntoElement for List {
type Element = Self;
fn element_id(&self) -> Option<crate::ElementId> {
None
}
fn into_element(self) -> Self::Element {
self
}
@ -761,7 +777,7 @@ mod test {
cx.draw(
point(px(0.), px(0.)),
size(px(100.), px(20.)).into(),
|_| list(state.clone()).w_full().h_full().z_index(10).into_any(),
|_| list(state.clone()).w_full().h_full().into_any(),
);
// Reset