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Fix scrolling in collab panel (#4105)

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When the `List` element's state is `ListState::reset()`, it eagerly
trashes it's cached element heights in anticipation of a prompt render.
But, due to the recent `display_layer` changes, that re-render is not
always forthcoming. This is a problem for `ListState::scroll()`, which
depends on these cached elements to correctly calculate the new logical
scroll offset.

Solutions we attempted:

- Cache the element heights and continue the scroll calculation 
- This was conceptually incorrect, reset should only be called when the
underlying data has been changed, making any calculation with the old
results meaningless.
- Lazily re-compute the element heights in scroll 
- Beyond being a non-trivial refactor, this would probably also cause us
to double-render the list in a single frame, which is bad.
- Cache the scroll offset and only calculate it in paint 
- This solution felt awkward to implement and meant we can't supply
synchronous list scroll events.
- Delay resetting until paint 
- This means that all of the other APIs that `ListState` supplies would
give temporarily incorrect results, worsening the problem

Given these issues, we settled on the solution with the least
compromises: drop scroll events if the state has been `reset()` between
`paint()` and `scroll()`. This shifts the responsibility for the problem
out of the List element and into consumers of `List`, if you want
perfectly smooth scrolling then you need to use `reset()` judiciously
and prefer `splice()`.

That said, I tested this by aggressively scrolling the Collab panel, and
it seems to work as well as it did before.

This PR also includes some initial testing infrastructure for working
with input from the platform and rendered elements.

Release Notes:

- N/A
This commit is contained in:
Mikayla Maki 2024-01-17 14:11:34 -08:00 • committed by GitHub
commit 6f40da77b6
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GPG key ID: B5690EEEBB952194
14 changed files with 351 additions and 207 deletions
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61
crates/gpui/src/window.rs
View file

@ -5,13 +5,14 @@ use crate::{
AsyncWindowContext, AvailableSpace, Bounds, BoxShadow, Context, Corners, CursorStyle,
DevicePixels, DispatchActionListener, DispatchNodeId, DispatchTree, DisplayId, Edges, Effect,
Entity, EntityId, EventEmitter, FileDropEvent, Flatten, FontId, GlobalElementId, GlyphId, Hsla,
ImageData, InputEvent, IsZero, KeyBinding, KeyContext, KeyDownEvent, KeystrokeEvent, LayoutId,
Model, ModelContext, Modifiers, MonochromeSprite, MouseButton, MouseMoveEvent, MouseUpEvent,
Path, Pixels, PlatformAtlas, PlatformDisplay, PlatformInputHandler, PlatformWindow, Point,
PolychromeSprite, PromptLevel, Quad, Render, RenderGlyphParams, RenderImageParams,
RenderSvgParams, ScaledPixels, Scene, Shadow, SharedString, Size, Style, SubscriberSet,
Subscription, Surface, TaffyLayoutEngine, Task, Underline, UnderlineStyle, View, VisualContext,
WeakView, WindowBounds, WindowOptions, SUBPIXEL_VARIANTS,
ImageData, IsZero, KeyBinding, KeyContext, KeyDownEvent, KeyEvent, KeystrokeEvent, LayoutId,
Model, ModelContext, Modifiers, MonochromeSprite, MouseButton, MouseEvent, MouseMoveEvent,
MouseUpEvent, Path, Pixels, PlatformAtlas, PlatformDisplay, PlatformInput,
PlatformInputHandler, PlatformWindow, Point, PolychromeSprite, PromptLevel, Quad, Render,
RenderGlyphParams, RenderImageParams, RenderSvgParams, ScaledPixels, Scene, Shadow,
SharedString, Size, Style, SubscriberSet, Subscription, Surface, TaffyLayoutEngine, Task,
Underline, UnderlineStyle, View, VisualContext, WeakView, WindowBounds, WindowOptions,
SUBPIXEL_VARIANTS,
};
use anyhow::{anyhow, Context as _, Result};
use collections::{FxHashMap, FxHashSet};
@ -971,7 +972,7 @@ impl<'a> WindowContext<'a> {
/// Register a mouse event listener on the window for the next frame. The type of event
/// is determined by the first parameter of the given listener. When the next frame is rendered
/// the listener will be cleared.
pub fn on_mouse_event<Event: 'static>(
pub fn on_mouse_event<Event: MouseEvent>(
&mut self,
mut handler: impl FnMut(&Event, DispatchPhase, &mut WindowContext) + 'static,
) {
@ -999,7 +1000,7 @@ impl<'a> WindowContext<'a> {
///
/// This is a fairly low-level method, so prefer using event handlers on elements unless you have
/// a specific need to register a global listener.
pub fn on_key_event<Event: 'static>(
pub fn on_key_event<Event: KeyEvent>(
&mut self,
listener: impl Fn(&Event, DispatchPhase, &mut WindowContext) + 'static,
) {
@ -1620,7 +1621,7 @@ impl<'a> WindowContext<'a> {
}
/// Dispatch a mouse or keyboard event on the window.
pub fn dispatch_event(&mut self, event: InputEvent) -> bool {
pub fn dispatch_event(&mut self, event: PlatformInput) -> bool {
// Handlers may set this to false by calling `stop_propagation`.
self.app.propagate_event = true;
// Handlers may set this to true by calling `prevent_default`.
@ -1629,37 +1630,37 @@ impl<'a> WindowContext<'a> {
let event = match event {
// Track the mouse position with our own state, since accessing the platform
// API for the mouse position can only occur on the main thread.
InputEvent::MouseMove(mouse_move) => {
PlatformInput::MouseMove(mouse_move) => {
self.window.mouse_position = mouse_move.position;
self.window.modifiers = mouse_move.modifiers;
InputEvent::MouseMove(mouse_move)
PlatformInput::MouseMove(mouse_move)
}
InputEvent::MouseDown(mouse_down) => {
PlatformInput::MouseDown(mouse_down) => {
self.window.mouse_position = mouse_down.position;
self.window.modifiers = mouse_down.modifiers;
InputEvent::MouseDown(mouse_down)
PlatformInput::MouseDown(mouse_down)
}
InputEvent::MouseUp(mouse_up) => {
PlatformInput::MouseUp(mouse_up) => {
self.window.mouse_position = mouse_up.position;
self.window.modifiers = mouse_up.modifiers;
InputEvent::MouseUp(mouse_up)
PlatformInput::MouseUp(mouse_up)
}
InputEvent::MouseExited(mouse_exited) => {
PlatformInput::MouseExited(mouse_exited) => {
self.window.modifiers = mouse_exited.modifiers;
InputEvent::MouseExited(mouse_exited)
PlatformInput::MouseExited(mouse_exited)
}
InputEvent::ModifiersChanged(modifiers_changed) => {
PlatformInput::ModifiersChanged(modifiers_changed) => {
self.window.modifiers = modifiers_changed.modifiers;
InputEvent::ModifiersChanged(modifiers_changed)
PlatformInput::ModifiersChanged(modifiers_changed)
}
InputEvent::ScrollWheel(scroll_wheel) => {
PlatformInput::ScrollWheel(scroll_wheel) => {
self.window.mouse_position = scroll_wheel.position;
self.window.modifiers = scroll_wheel.modifiers;
InputEvent::ScrollWheel(scroll_wheel)
PlatformInput::ScrollWheel(scroll_wheel)
}
// Translate dragging and dropping of external files from the operating system
// to internal drag and drop events.
InputEvent::FileDrop(file_drop) => match file_drop {
PlatformInput::FileDrop(file_drop) => match file_drop {
FileDropEvent::Entered { position, paths } => {
self.window.mouse_position = position;
if self.active_drag.is_none() {
@ -1669,7 +1670,7 @@ impl<'a> WindowContext<'a> {
cursor_offset: position,
});
}
InputEvent::MouseMove(MouseMoveEvent {
PlatformInput::MouseMove(MouseMoveEvent {
position,
pressed_button: Some(MouseButton::Left),
modifiers: Modifiers::default(),
@ -1677,7 +1678,7 @@ impl<'a> WindowContext<'a> {
}
FileDropEvent::Pending { position } => {
self.window.mouse_position = position;
InputEvent::MouseMove(MouseMoveEvent {
PlatformInput::MouseMove(MouseMoveEvent {
position,
pressed_button: Some(MouseButton::Left),
modifiers: Modifiers::default(),
@ -1686,21 +1687,21 @@ impl<'a> WindowContext<'a> {
FileDropEvent::Submit { position } => {
self.activate(true);
self.window.mouse_position = position;
InputEvent::MouseUp(MouseUpEvent {
PlatformInput::MouseUp(MouseUpEvent {
button: MouseButton::Left,
position,
modifiers: Modifiers::default(),
click_count: 1,
})
}
FileDropEvent::Exited => InputEvent::MouseUp(MouseUpEvent {
FileDropEvent::Exited => PlatformInput::MouseUp(MouseUpEvent {
button: MouseButton::Left,
position: Point::default(),
modifiers: Modifiers::default(),
click_count: 1,
}),
},
InputEvent::KeyDown(_) | InputEvent::KeyUp(_) => event,
PlatformInput::KeyDown(_) | PlatformInput::KeyUp(_) => event,
};
if let Some(any_mouse_event) = event.mouse_event() {
@ -2983,7 +2984,7 @@ impl<'a, V: 'static> ViewContext<'a, V> {
/// Add a listener for any mouse event that occurs in the window.
/// This is a fairly low level method.
/// Typically, you'll want to use methods on UI elements, which perform bounds checking etc.
pub fn on_mouse_event<Event: 'static>(
pub fn on_mouse_event<Event: MouseEvent>(
&mut self,
handler: impl Fn(&mut V, &Event, DispatchPhase, &mut ViewContext<V>) + 'static,
) {
@ -2996,7 +2997,7 @@ impl<'a, V: 'static> ViewContext<'a, V> {
}
/// Register a callback to be invoked when the given Key Event is dispatched to the window.
pub fn on_key_event<Event: 'static>(
pub fn on_key_event<Event: KeyEvent>(
&mut self,
handler: impl Fn(&mut V, &Event, DispatchPhase, &mut ViewContext<V>) + 'static,
) {