Files
Ez2Lazer/osu.Game/Graphics/Carousel/Carousel.cs

1195 lines
48 KiB
C#

// Copyright (c) ppy Pty Ltd <contact@ppy.sh>. Licensed under the MIT Licence.
// See the LICENCE file in the repository root for full licence text.
using System;
using System.Collections.Generic;
using System.Diagnostics;
using System.Linq;
using System.Threading;
using System.Threading.Tasks;
using osu.Framework.Allocation;
using osu.Framework.Audio;
using osu.Framework.Audio.Sample;
using osu.Framework.Bindables;
using osu.Framework.Caching;
using osu.Framework.Development;
using osu.Framework.Extensions.PolygonExtensions;
using osu.Framework.Extensions.TypeExtensions;
using osu.Framework.Graphics;
using osu.Framework.Graphics.Containers;
using osu.Framework.Graphics.Cursor;
using osu.Framework.Graphics.Pooling;
using osu.Framework.Input.Bindings;
using osu.Framework.Input.Events;
using osu.Framework.Layout;
using osu.Framework.Logging;
using osu.Framework.Utils;
using osu.Game.Graphics.Containers;
using osu.Game.Input.Bindings;
using osu.Game.Online.Multiplayer;
using osuTK;
using osuTK.Input;
namespace osu.Game.Graphics.Carousel
{
/// <summary>
/// A highly efficient vertical list display that is used primarily for the song select screen,
/// but flexible enough to be used for other use cases.
/// </summary>
public abstract partial class Carousel<T> : CompositeDrawable, IKeyBindingHandler<GlobalAction>
where T : notnull
{
#region Properties and methods for external usage
/// <summary>
/// Called after a filter operation or change in items results in the visible carousel items changing.
/// </summary>
public Action<IEnumerable<CarouselItem>>? NewItemsPresented { private get; init; }
/// <summary>
/// Height of the area above the carousel that should be treated as visible due to transparency of elements in front of it.
/// </summary>
public float BleedTop { get; set; }
/// <summary>
/// Height of the area below the carousel that should be treated as visible due to transparency of elements in front of it.
/// </summary>
public float BleedBottom { get; set; }
/// <summary>
/// The number of pixels outside the carousel's vertical bounds to manifest drawables.
/// This allows preloading content before it scrolls into view.
/// </summary>
public float DistanceOffscreenToPreload { get; set; }
/// <summary>
/// When a new request arrives to change filtering, the number of milliseconds to wait before performing the filter.
/// Regardless of any external debouncing, this is a safety measure to avoid triggering too many threaded operations.
/// </summary>
public int DebounceDelay { get; set; }
/// <summary>
/// Whether an asynchronous filter / group operation is currently underway.
/// </summary>
public bool IsFiltering => !filterTask.IsCompleted;
/// <summary>
/// The number of times filter operations have been triggered.
/// </summary>
internal int FilterCount { get; private set; }
/// <summary>
/// The number of displayable items currently being tracked (before filtering).
/// </summary>
public int ItemsTracked => Items.Count;
/// <summary>
/// The items currently in rotation for display.
/// </summary>
public int DisplayableItems => carouselItems?.Count ?? 0;
/// <summary>
/// The number of items currently actualised into drawables.
/// </summary>
public int VisibleItems => Scroll.Panels.Count;
/// <summary>
/// The currently selected model. Generally of type T.
/// </summary>
/// <remarks>
/// A carousel may create panels for non-T types.
/// To keep things simple, we therefore avoid generic constraints on the current selection.
///
/// The selection is never reset due to not existing. It can be set to anything.
/// If no matching carousel item exists, there will be no visually selected item while waiting for potential new item which matches.
/// </remarks>
public object? CurrentSelection
{
get => currentSelection.Model;
set
{
if (!CheckModelEquality(currentSelection.Model, value))
{
HandleItemSelected(value);
if (currentSelection.Model != null)
HandleItemDeselected(currentSelection.Model);
currentKeyboardSelection = new Selection(value);
currentSelection = currentKeyboardSelection;
selectionValid.Invalidate();
}
else if (currentKeyboardSelection.Model != value)
{
// Even if the current selection matches, let's ensure the keyboard selection is reset
// to the newly selected object. This matches user expectations (for now).
currentKeyboardSelection = currentSelection;
selectionValid.Invalidate();
}
}
}
/// <summary>
/// Activate the specified item.
/// </summary>
/// <param name="item"></param>
public void Activate(CarouselItem item)
{
// Regardless of how the item handles activation, update keyboard selection to the activated panel.
// In other words, when a panel is clicked, keyboard selection should default to matching the clicked
// item.
setKeyboardSelection(item.Model);
(GetMaterialisedDrawableForItem(item) as ICarouselPanel)?.Activated();
HandleItemActivated(item);
selectionValid.Invalidate();
}
/// <summary>
/// Scroll carousel to the selected item if available.
/// </summary>
public void ScrollToSelection() => scrollToSelection.Invalidate();
/// <summary>
/// Returns the vertical spacing between two given carousel items. Negative value can be used to create an overlapping effect.
/// </summary>
protected virtual float GetSpacingBetweenPanels(CarouselItem top, CarouselItem bottom) => 0f;
#endregion
#region Properties and methods concerning implementations
/// <summary>
/// A collection of filters which should be run each time a <see cref="FilterAsync"/> is executed.
/// </summary>
/// <remarks>
/// Implementations should add all required filters as part of their initialisation.
///
/// Importantly, each filter is sequentially run in the order provided.
/// Each filter receives the output of the previous filter.
///
/// A filter may add, mutate or remove items.
/// </remarks>
public IEnumerable<ICarouselFilter> Filters { get; init; } = Enumerable.Empty<ICarouselFilter>();
/// <summary>
/// All items which are to be considered for display in this carousel.
/// Mutating this list will automatically queue a <see cref="FilterAsync"/>.
/// </summary>
/// <remarks>
/// Note that an <see cref="ICarouselFilter"/> may add new items which are displayed but not tracked in this list.
/// </remarks>
protected readonly BindableList<T> Items = new BindableList<T>();
/// <summary>
/// Queue an asynchronous filter operation.
/// </summary>
/// <param name="clearExistingPanels">Whether all existing drawable panels should be reset post filter.</param>
protected virtual Task<IEnumerable<CarouselItem>> FilterAsync(bool clearExistingPanels = false)
{
FilterCount++;
if (clearExistingPanels)
filterReusesPanels.Invalidate();
filterAfterItemsChanged.Validate();
filterTask = performFilter();
filterTask.FireAndForget();
return filterTask;
}
/// <summary>
/// Fired after a filter operation completed.
/// </summary>
protected virtual void HandleFilterCompleted()
{
}
/// <summary>
/// Check whether two models are the same for display purposes.
/// </summary>
protected virtual bool CheckModelEquality(object? x, object? y) => ReferenceEquals(x, y);
/// <summary>
/// Create a drawable for the given carousel item so it can be displayed.
/// </summary>
/// <remarks>
/// For efficiency, it is recommended the drawables are retrieved from a <see cref="DrawablePool{T}"/>.
/// </remarks>
/// <param name="item">The item which should be represented by the returned drawable.</param>
/// <returns>The manifested drawable.</returns>
protected abstract Drawable GetDrawableForDisplay(CarouselItem item);
/// <summary>
/// Given a <see cref="CarouselItem"/>, find a drawable representation if it is currently displayed in the carousel.
/// </summary>
/// <remarks>
/// This will only return a drawable if it is "on-screen".
/// </remarks>
/// <param name="item">The item to find a related drawable representation.</param>
/// <returns>The drawable representation if it exists.</returns>
protected Drawable? GetMaterialisedDrawableForItem(CarouselItem item) =>
Scroll.Panels.SingleOrDefault(p => ((ICarouselPanel)p).Item == item);
/// <summary>
/// When a user is traversing the carousel via group selection keys, assert whether the item provided is a valid target.
/// </summary>
/// <param name="item">The candidate item.</param>
/// <returns>Whether the provided item is a valid group target. If <c>false</c>, more panels will be checked in the user's requested direction until a valid target is found.</returns>
protected virtual bool CheckValidForGroupSelection(CarouselItem item) => false;
/// <summary>
/// When a user is traversing the carousel via set selection keys, assert whether the item provided is a valid target.
/// </summary>
/// <param name="item">The candidate item.</param>
/// <returns>Whether the provided item is a valid set target. If <c>false</c>, more panels will be checked in the user's requested direction until a valid target is found.</returns>
protected virtual bool CheckValidForSetSelection(CarouselItem item) => true;
/// <summary>
/// Keyboard selection usually does not automatically activate an item. There may be exceptions to this rule.
/// Returning <c>true</c> here will make keyboard traversal act like set traversal for the target item.
/// </summary>
protected virtual bool ShouldActivateOnKeyboardSelection(CarouselItem item) => false;
/// <summary>
/// Called after an item becomes the <see cref="CurrentSelection"/>.
/// Should be used to handle any set expansion, item visibility changes, etc.
/// </summary>
protected virtual void HandleItemSelected(object? model) { }
/// <summary>
/// Called when the <see cref="CurrentSelection"/> changes to a new selection.
/// Should be used to handle any set expansion, item visibility changes, etc.
/// </summary>
protected virtual void HandleItemDeselected(object? model) { }
/// <summary>
/// Called when an item is activated via user input (keyboard traversal or a mouse click).
/// </summary>
/// <remarks>
/// An activated item should decide to perform an action, such as:
/// - Change its expanded state (and show / hide children items).
/// - Set the item to the <see cref="CurrentSelection"/>.
/// - Start gameplay on a beatmap difficulty if already selected.
/// </remarks>
/// <param name="item">The carousel item which was activated.</param>
protected virtual void HandleItemActivated(CarouselItem item) { }
#endregion
#region Initialisation
protected readonly CarouselScrollContainer Scroll;
protected Carousel()
{
InternalChild = Scroll = new CarouselScrollContainer
{
Masking = false,
RelativeSizeAxes = Axes.Both,
};
Items.BindCollectionChanged((_, _) => filterAfterItemsChanged.Invalidate());
}
[BackgroundDependencyLoader]
private void load(AudioManager audio)
{
loadSamples(audio);
}
#endregion
#region Filtering and display preparation
/// <summary>
/// Retrieve a list of all <see cref="CarouselItem"/>s currently displayed.
/// </summary>
public IList<CarouselItem>? GetCarouselItems() => carouselItems;
private List<CarouselItem>? carouselItems;
private Task<IEnumerable<CarouselItem>> filterTask = Task.FromResult(Enumerable.Empty<CarouselItem>());
private CancellationTokenSource cancellationSource = new CancellationTokenSource();
/// <summary>
/// For background re-filters, ensure we wait for the previous filter operation to complete before starting another.
/// This avoids the carousel never updating its display in high churn scenarios.
/// </summary>
private readonly Cached filterAfterItemsChanged = new Cached();
private async Task<IEnumerable<CarouselItem>> performFilter()
{
Stopwatch stopwatch = Stopwatch.StartNew();
var cts = new CancellationTokenSource();
var previousCancellationSource = Interlocked.Exchange(ref cancellationSource, cts);
await previousCancellationSource.CancelAsync().ConfigureAwait(true);
if (DebounceDelay > 0)
{
log($"Filter operation queued, waiting for {DebounceDelay} ms debounce");
await Task.Delay(DebounceDelay, cts.Token).ConfigureAwait(true);
}
// Copy must be performed on update thread for now (see ConfigureAwait above).
// Could potentially be optimised in the future if it becomes an issue.
Debug.Assert(ThreadSafety.IsUpdateThread);
List<CarouselItem> items = new List<CarouselItem>(Items.Select(m => new CarouselItem(m)));
await Task.Run(async () =>
{
try
{
foreach (var filter in Filters)
{
log($"Performing {filter.GetType().ReadableName()}");
items = await filter.Run(items, cts.Token).ConfigureAwait(false);
// To avoid shooting ourselves in the foot, ensure that we manifest a list after each filter.
//
// A future improvement may be passing a reference list through each filter rather than copying each time,
// but this is the safest approach.
}
log("Updating Y positions");
updateYPositions(items, visibleHalfHeight);
}
catch (OperationCanceledException)
{
log("Cancelled due to newer request arriving");
}
}, cts.Token).ConfigureAwait(false);
if (cts.Token.IsCancellationRequested)
return Enumerable.Empty<CarouselItem>();
Schedule(() =>
{
log("Items ready for display");
carouselItems = items;
displayedRange = null;
if (!filterReusesPanels.IsValid)
{
foreach (var panel in Scroll.Panels)
expirePanel(panel);
filterReusesPanels.Validate();
}
HandleFilterCompleted();
refreshAfterSelection();
if (!Scroll.UserScrolling)
ScrollToSelection();
NewItemsPresented?.Invoke(carouselItems);
});
return items;
void log(string text) => Logger.Log($"Carousel[op {cts.GetHashCode().ToString()}] {stopwatch.ElapsedMilliseconds} ms: {text}");
}
private void updateYPositions(IEnumerable<CarouselItem> carouselItems, float offset)
{
CarouselItem? previousVisible = null;
foreach (var item in carouselItems)
updateItemYPosition(item, ref previousVisible, ref offset);
}
private void updateItemYPosition(CarouselItem item, ref CarouselItem? previousVisible, ref float offset)
{
float spacing = previousVisible == null || !item.IsVisible ? 0 : GetSpacingBetweenPanels(previousVisible, item);
offset += spacing;
item.CarouselYPosition = offset;
// ensure there are no input gaps where clicking will fall through the carousel.
// notably, only do this where there's positive spacing between panels (negative spacing means they overlap already and there is no gap to fill).
if (spacing > 0)
{
item.CarouselInputLenienceAbove = spacing / 2;
if (previousVisible != null)
previousVisible.CarouselInputLenienceBelow = item.CarouselInputLenienceAbove;
}
if (item.IsVisible)
{
offset += item.DrawHeight;
previousVisible = item;
}
}
#endregion
#region Input handling
protected override bool OnKeyDown(KeyDownEvent e)
{
switch (e.Key)
{
// this is a special hard-coded case; we can't rely on OnPressed as GlobalActionContainer is
// matching with exact modifier consideration (so Ctrl+Enter would be ignored).
case Key.Enter:
case Key.KeypadEnter:
activateSelection();
return true;
}
return base.OnKeyDown(e);
}
public bool OnPressed(KeyBindingPressEvent<GlobalAction> e)
{
switch (e.Action)
{
case GlobalAction.Select:
activateSelection();
return true;
// the selection traversal handlers below are scheduled to avoid an issue
// wherein if the update frame rate is low, keeping one of the actions below pressed leads to selection moving back to the start / end.
// the reason why that happens is that the code managing `current(Keyboard)?Selection` can lose track of the index of the selected item
// if the selection is changed more than once during an update frame,
// which can happen if repeat inputs are enqueued for processing at a rate faster than the update refresh rate.
// `refreshAfterSelection()` is the method responsible for updating the index of the selected item here which runs once per frame.
case GlobalAction.SelectPrevious:
Scheduler.AddOnce(traverseFromKey, new TraversalOperation(TraversalType.Keyboard, -1));
return true;
case GlobalAction.SelectNext:
Scheduler.AddOnce(traverseFromKey, new TraversalOperation(TraversalType.Keyboard, 1));
return true;
case GlobalAction.ActivatePreviousSet:
Scheduler.AddOnce(traverseFromKey, new TraversalOperation(TraversalType.Set, -1));
return true;
case GlobalAction.ActivateNextSet:
Scheduler.AddOnce(traverseFromKey, new TraversalOperation(TraversalType.Set, 1));
return true;
case GlobalAction.ExpandPreviousGroup:
Scheduler.AddOnce(traverseFromKey, new TraversalOperation(TraversalType.Group, -1));
return true;
case GlobalAction.ExpandNextGroup:
Scheduler.AddOnce(traverseFromKey, new TraversalOperation(TraversalType.Group, 1));
return true;
case GlobalAction.ToggleCurrentGroup:
if (carouselItems == null || carouselItems.Count == 0)
return true;
if (currentKeyboardSelection.CarouselItem == null || currentKeyboardSelection.Index == null)
return true;
if (CheckValidForGroupSelection(currentKeyboardSelection.CarouselItem))
{
// If keyboard selection is a group, toggle group and then change keyboard selection to actual selection.
Activate(currentKeyboardSelection.CarouselItem);
}
else
{
// If current keyboard selection is not a group, toggle the closest group and move keyboard selection to that group.
for (int i = currentKeyboardSelection.Index.Value; i >= 0; i--)
{
var newItem = carouselItems[i];
if (CheckValidForGroupSelection(newItem))
{
Activate(newItem);
return true;
}
}
}
return true;
}
return false;
void traverseFromKey(TraversalOperation traversal)
{
switch (traversal.Type)
{
case TraversalType.Keyboard:
traverseKeyboardSelection(traversal.Direction);
break;
case TraversalType.Set:
traverseSetSelection(traversal.Direction);
break;
case TraversalType.Group:
traverseGroupSelection(traversal.Direction);
break;
default:
throw new ArgumentOutOfRangeException();
}
}
}
private enum TraversalType { Keyboard, Set, Group }
private record TraversalOperation(TraversalType Type, int Direction);
public void OnReleased(KeyBindingReleaseEvent<GlobalAction> e)
{
}
private void activateSelection()
{
if (currentKeyboardSelection.CarouselItem != null)
Activate(currentKeyboardSelection.CarouselItem);
}
private void traverseKeyboardSelection(int direction)
{
if (carouselItems == null || carouselItems.Count == 0) return;
int originalIndex;
if (currentKeyboardSelection.Index != null)
originalIndex = currentKeyboardSelection.Index.Value;
else if (direction > 0)
originalIndex = carouselItems.Count - 1;
else
originalIndex = 0;
int newIndex = originalIndex;
// Iterate over every item back to the current selection, finding the first valid item.
// The fail condition is when we reach the selection after a cyclic loop over every item.
do
{
newIndex = (newIndex + direction + carouselItems.Count) % carouselItems.Count;
var newItem = carouselItems[newIndex];
if (newItem.IsVisible)
{
if (!CheckModelEquality(currentSelection.Model, newItem.Model) && ShouldActivateOnKeyboardSelection(newItem))
Activate(newItem);
else
{
playTraversalSound();
setKeyboardSelection(newItem.Model);
}
return;
}
} while (newIndex != originalIndex);
}
/// <summary>
/// Select the next valid group selection relative to a current selection.
/// This is generally for keyboard based traversal.
/// </summary>
/// <param name="direction">Positive for downwards, negative for upwards.</param>
/// <returns>Whether selection was possible.</returns>
private void traverseGroupSelection(int direction) => traverseSelection(direction, CheckValidForGroupSelection);
/// <summary>
/// Select the next valid set selection relative to a current selection.
/// This is generally for keyboard based traversal.
/// </summary>
/// <param name="direction">Positive for downwards, negative for upwards.</param>
/// <returns>Whether selection was possible.</returns>
private void traverseSetSelection(int direction)
{
// If the user has a different keyboard selection and requests
// set selection, first transfer the keyboard selection to actual selection.
//
// It is assumed that selecting a set will immediately change selection to one of its children.
if (currentKeyboardSelection.CarouselItem != null && currentSelection.CarouselItem != currentKeyboardSelection.CarouselItem)
{
Activate(currentKeyboardSelection.CarouselItem);
return;
}
traverseSelection(direction, CheckValidForSetSelection);
}
private void traverseSelection(int direction, Func<CarouselItem, bool> predicate)
{
if (carouselItems == null || carouselItems.Count == 0) return;
int originalIndex;
int newIndex;
if (currentKeyboardSelection.Index == null)
{
// If there's no current selection, start from either end of the full list.
newIndex = originalIndex = direction > 0 ? carouselItems.Count - 1 : 0;
}
else
{
newIndex = originalIndex = currentKeyboardSelection.Index.Value;
// As a second special case, if we're set selecting backwards and the current selection isn't a set,
// make sure to go back to the set header this item belongs to, so that the block below doesn't find it and stop too early.
if (direction < 0)
{
while (newIndex > 0 && !predicate(carouselItems[newIndex]))
newIndex--;
}
}
// Iterate over every item back to the current selection, finding the first valid item.
// The fail condition is when we reach the selection after a cyclic loop over every item.
do
{
newIndex = (newIndex + direction + carouselItems.Count) % carouselItems.Count;
if (newIndex == originalIndex)
break;
var newItem = carouselItems[newIndex];
if (!newItem.IsExpanded && predicate(newItem))
{
Activate(newItem);
return;
}
} while (true);
}
#endregion
#region Audio
private Sample? sampleKeyboardTraversal;
private double audioFeedbackLastPlaybackTime;
private void loadSamples(AudioManager audio)
{
sampleKeyboardTraversal = audio.Samples.Get(@"SongSelect/select-difficulty");
}
private void playTraversalSound()
{
if (Time.Current - audioFeedbackLastPlaybackTime >= OsuGameBase.SAMPLE_DEBOUNCE_TIME)
{
sampleKeyboardTraversal?.Play();
audioFeedbackLastPlaybackTime = Time.Current;
}
}
#endregion
#region Selection handling
/// <summary>
/// The currently selected <see cref="CarouselItem"/>, if any is selected.
/// </summary>
protected CarouselItem? CurrentSelectionItem => currentSelection.CarouselItem;
/// <summary>
/// The index in <see cref="GetCarouselItems"/> of the current selection, if available.
/// </summary>
protected int? CurrentSelectionIndex => currentSelection.Index;
/// <summary>
/// Becomes invalid when the current selection has changed and needs to be updated visually.
/// </summary>
private readonly Cached selectionValid = new Cached();
private Selection currentKeyboardSelection = new Selection();
private Selection currentSelection = new Selection();
private void setKeyboardSelection(object? model)
{
currentKeyboardSelection = new Selection(model);
selectionValid.Invalidate();
}
/// <summary>
/// Call after a selection of items change to re-attach <see cref="CarouselItem"/>s to current <see cref="Selection"/>s.
/// </summary>
private void refreshAfterSelection()
{
float yPos = visibleHalfHeight;
// Invalidate display range as panel positions and visible status may have changed.
// Position transfer won't happen unless we invalidate this.
displayedRange = null;
Selection prevKeyboard = currentKeyboardSelection;
// Importantly, we also reset the `Selection` to the most basic state.
// Removing the index and carousel item here is important to ensure we are aware of if a selection has been filtered away.
// If it hasn't been filtered, the full details will be re-populated just below in the loop.
currentKeyboardSelection = new Selection(currentKeyboardSelection.Model);
currentSelection = new Selection(currentSelection.Model);
if (carouselItems == null)
return;
CarouselItem? lastVisible = null;
int count = carouselItems.Count;
// We are performing two important operations here:
// - Update all Y positions. After a selection occurs, panels may have changed visibility state and therefore Y positions.
// - Link selected models to CarouselItems. If a selection changed, this is where we find the relevant CarouselItems for further use.
for (int i = 0; i < count; i++)
{
var item = carouselItems[i];
updateItemYPosition(item, ref lastVisible, ref yPos);
if (CheckModelEquality(item.Model, currentKeyboardSelection.Model!))
currentKeyboardSelection = new Selection(currentKeyboardSelection.Model, item, item.CarouselYPosition, i);
if (CheckModelEquality(item.Model, currentSelection.Model!))
currentSelection = new Selection(currentSelection.Model, item, item.CarouselYPosition, i);
}
// Update the total height of all items (to make the scroll container scrollable through the full height even though
// most items are not displayed / loaded).
Scroll.SetLayoutHeight(yPos + visibleHalfHeight);
// If a keyboard selection is currently made, we want to keep the view stable around the selection.
// That means that we should offset the immediate scroll position by any change in Y position for the selection.
if (prevKeyboard.YPosition != null && currentKeyboardSelection.YPosition != null && currentKeyboardSelection.YPosition != prevKeyboard.YPosition)
Scroll.OffsetScrollPosition((float)(currentKeyboardSelection.YPosition!.Value - prevKeyboard.YPosition.Value));
}
#endregion
#region Display handling
private DisplayRange? displayedRange;
private readonly CarouselItem carouselBoundsItem = new CarouselItem(new object());
/// <summary>
/// The position of the lower visible bound with respect to the current scroll position.
/// </summary>
private float visibleBottomBound;
/// <summary>
/// The position of the upper visible bound with respect to the current scroll position.
/// </summary>
private float visibleUpperBound;
/// <summary>
/// Half the height of the visible content.
/// </summary>
private float visibleHalfHeight;
/// <summary>
/// Whether existing panels can be re-used in the next filter.
/// </summary>
private readonly Cached filterReusesPanels = new Cached();
/// <summary>
/// Scrolling to selection relies on <see cref="currentKeyboardSelection"/> being fully populated.
/// This flag ensures it runs after <see cref="refreshAfterSelection"/> validates this.
/// </summary>
private readonly Cached scrollToSelection = new Cached();
protected override void Update()
{
base.Update();
if (carouselItems == null)
return;
visibleBottomBound = (float)(Scroll.Current + DrawHeight + BleedBottom);
visibleUpperBound = (float)(Scroll.Current - BleedTop);
visibleHalfHeight = (DrawHeight + BleedBottom + BleedTop) / 2;
if (!selectionValid.IsValid)
{
refreshAfterSelection();
// Always scroll to selection in this case (regardless of `UserScrolling` state), centering the selection.
ScrollToSelection();
selectionValid.Validate();
}
var range = getDisplayRange();
if (range != displayedRange)
{
displayedRange = range;
updateDisplayedRange(range);
}
double selectedYPos = currentSelection.CarouselItem?.CarouselYPosition ?? 0;
foreach (var panel in Scroll.Panels)
{
var c = (ICarouselPanel)panel;
// panel in the process of expiring, ignore it.
if (c.Item == null)
continue;
float normalisedDepth = (float)(Math.Abs(selectedYPos - c.Item.CarouselYPosition) / DrawHeight);
Scroll.Panels.ChangeChildDepth(panel, c.Item.DepthLayer + normalisedDepth);
if (c.DrawYPosition != c.Item.CarouselYPosition)
c.DrawYPosition = Interpolation.DampContinuously(c.DrawYPosition, c.Item.CarouselYPosition, 50, Time.Elapsed);
panel.X = GetPanelXOffset(panel);
c.Selected.Value = currentSelection?.CarouselItem != null && CheckModelEquality(c.Item, currentSelection.CarouselItem);
c.KeyboardSelected.Value = c.Item == currentKeyboardSelection?.CarouselItem;
c.Expanded.Value = c.Item.IsExpanded;
}
if (!filterAfterItemsChanged.IsValid && !IsFiltering)
FilterAsync();
}
protected override void UpdateAfterChildren()
{
base.UpdateAfterChildren();
if (!scrollToSelection.IsValid)
{
if (currentKeyboardSelection.YPosition != null)
Scroll.ScrollTo(currentKeyboardSelection.YPosition.Value - visibleHalfHeight + BleedTop);
scrollToSelection.Validate();
}
}
protected virtual float GetPanelXOffset(Drawable panel)
{
Vector2 posInScroll = Scroll.ToLocalSpace(panel.ScreenSpaceDrawQuad.Centre);
float dist = Math.Abs(1f - (posInScroll.Y + BleedTop) / visibleHalfHeight);
return offsetX(dist, visibleHalfHeight);
}
/// <summary>
/// Computes the x-offset of currently visible items. Makes the carousel appear round.
/// </summary>
/// <param name="dist">
/// Vertical distance from the center of the carousel container
/// ranging from -1 to 1.
/// </param>
/// <param name="halfHeight">Half the height of the carousel container.</param>
private static float offsetX(float dist, float halfHeight)
{
// The radius of the circle the carousel moves on.
const float circle_radius = 3;
float discriminant = MathF.Max(0, circle_radius * circle_radius - dist * dist);
return (circle_radius - MathF.Sqrt(discriminant)) * halfHeight;
}
private DisplayRange getDisplayRange()
{
Debug.Assert(carouselItems != null);
if (carouselItems.Count == 0)
return DisplayRange.EMPTY;
// Find index range of all items that should be on-screen
carouselBoundsItem.CarouselYPosition = visibleUpperBound - DistanceOffscreenToPreload;
int firstIndex = carouselItems.BinarySearch(carouselBoundsItem);
if (firstIndex < 0) firstIndex = ~firstIndex;
carouselBoundsItem.CarouselYPosition = visibleBottomBound + DistanceOffscreenToPreload;
int lastIndex = carouselItems.BinarySearch(carouselBoundsItem);
if (lastIndex < 0) lastIndex = ~lastIndex;
firstIndex = Math.Max(0, firstIndex - 1);
lastIndex = Math.Max(0, lastIndex - 1);
return new DisplayRange(firstIndex, lastIndex);
}
private void updateDisplayedRange(DisplayRange range)
{
Debug.Assert(carouselItems != null);
List<CarouselItem> toDisplay = range == DisplayRange.EMPTY
? new List<CarouselItem>()
: carouselItems.GetRange(range.First, range.Last - range.First + 1);
toDisplay.RemoveAll(i => !i.IsVisible);
// Iterate over all panels which are already displayed and figure which need to be displayed / removed.
foreach (var panel in Scroll.Panels)
{
var carouselPanel = (ICarouselPanel)panel;
if (carouselPanel.Item == null)
{
// Item is null when a panel is already fading away from existence; should be ignored for tracking purposes.
continue;
}
var existing = toDisplay.FirstOrDefault(i => CheckModelEquality(i.Model, carouselPanel.Item!.Model));
if (existing != null)
{
carouselPanel.Item = existing;
toDisplay.Remove(existing);
continue;
}
// If the new display range doesn't contain the panel, it's no longer required for display.
expirePanel(panel);
}
// Add any new items which need to be displayed and haven't yet.
foreach (var item in toDisplay)
{
var drawable = GetDrawableForDisplay(item);
if (drawable is not ICarouselPanel carouselPanel)
throw new InvalidOperationException($"Carousel panel drawables must implement {typeof(ICarouselPanel)}");
carouselPanel.Item = item;
carouselPanel.DrawYPosition = item.CarouselYPosition;
Scroll.Add(drawable);
}
if (toDisplay.Any())
{
// To make transitions of items appearing in the flow look good, do a pass and make sure newly added items spawn from
// just beneath the *current interpolated position* of the previous panel.
var orderedPanels = Scroll.Panels
.Where(p => Scroll.ScreenSpaceDrawQuad.Intersects(p.ScreenSpaceDrawQuad))
.OfType<ICarouselPanel>()
.Where(p => p.Item != null)
.OrderBy(p => p.Item!.CarouselYPosition)
.ToList();
for (int i = 0; i < orderedPanels.Count; i++)
{
var panel = orderedPanels[i];
if (toDisplay.Contains(panel.Item!))
{
// Don't apply to the last because animating the tail of the list looks bad.
// It's usually off-screen anyway.
if (i > 0 && i < orderedPanels.Count - 1)
panel.DrawYPosition = orderedPanels[i - 1].DrawYPosition;
}
}
}
}
private void expirePanel(Drawable panel)
{
var carouselPanel = (ICarouselPanel)panel;
// expired panels should have a depth behind all other panels to make the transition not look weird.
Scroll.Panels.ChangeChildDepth(panel, panel.Depth + 1024);
panel.FadeOut(150, Easing.OutQuint);
panel.MoveToX(panel.X + 100, 200, Easing.Out);
panel.Expire();
carouselPanel.Item = null;
carouselPanel.Selected.Value = false;
carouselPanel.KeyboardSelected.Value = false;
carouselPanel.Expanded.Value = false;
}
protected override bool OnInvalidate(Invalidation invalidation, InvalidationSource source)
{
// handles the vertical size of the carousel changing (ie. on window resize when aspect ratio has changed).
if (invalidation.HasFlag(Invalidation.DrawSize))
selectionValid.Invalidate();
return base.OnInvalidate(invalidation, source);
}
#endregion
#region Internal helper classes
/// <summary>
/// Bookkeeping for a current selection.
/// </summary>
/// <param name="Model">The selected model. If <c>null</c>, there's no selection.</param>
/// <param name="CarouselItem">A related carousel item representation for the model. May be null if selection is not present as an item, or if <see cref="Carousel{T}.refreshAfterSelection"/> has not been run yet.</param>
/// <param name="YPosition">The Y position of the selection as of the last run of <see cref="Carousel{T}.refreshAfterSelection"/>. May be null if selection is not present as an item, or if <see cref="Carousel{T}.refreshAfterSelection"/> has not been run yet.</param>
/// <param name="Index">The index of the selection as of the last run of <see cref="Carousel{T}.refreshAfterSelection"/>. May be null if selection is not present as an item, or if <see cref="Carousel{T}.refreshAfterSelection"/> has not been run yet.</param>
private record Selection(object? Model = null, CarouselItem? CarouselItem = null, double? YPosition = null, int? Index = null);
private record DisplayRange(int First, int Last)
{
public static readonly DisplayRange EMPTY = new DisplayRange(-1, -1);
}
/// <summary>
/// Implementation of scroll container which handles very large vertical lists by internally using <c>double</c> precision
/// for pre-display Y values.
/// </summary>
public partial class CarouselScrollContainer : UserTrackingScrollContainer, IKeyBindingHandler<GlobalAction>
{
public readonly Container Panels;
public void SetLayoutHeight(float height) => Panels.Height = height;
/// <summary>
/// Allow handling right click scroll outside of the carousel's display area.
/// </summary>
public override bool ReceivePositionalInputAt(Vector2 screenSpacePos) => true;
public CarouselScrollContainer()
{
// Managing our own custom layout within ScrollContent causes feedback with public ScrollContainer calculations,
// so we must maintain one level of separation from ScrollContent.
base.Add(Panels = new Container
{
Name = "Layout content",
RelativeSizeAxes = Axes.X,
});
}
public override void OffsetScrollPosition(double offset)
{
base.OffsetScrollPosition(offset);
foreach (var panel in Panels)
((ICarouselPanel)panel).DrawYPosition += offset;
}
public override void Clear(bool disposeChildren)
{
Panels.Height = 0;
Panels.Clear(disposeChildren);
}
public override void Add(Drawable drawable)
{
if (drawable is not ICarouselPanel)
throw new InvalidOperationException($"Carousel panel drawables must implement {typeof(ICarouselPanel)}");
Panels.Add(drawable);
}
public override double GetChildPosInContent(Drawable d, Vector2 offset)
{
if (d is not ICarouselPanel panel)
return base.GetChildPosInContent(d, offset);
return panel.DrawYPosition + offset.X;
}
protected override void ApplyCurrentToContent()
{
Debug.Assert(ScrollDirection == Direction.Vertical);
double scrollableExtent = -Current + ScrollableExtent * ScrollContent.RelativeAnchorPosition.Y;
foreach (var d in Panels)
d.Y = (float)(((ICarouselPanel)d).DrawYPosition + scrollableExtent);
}
#region Scrollbar padding
public float ScrollbarPaddingTop { get; set; } = 5;
public float ScrollbarPaddingBottom { get; set; } = 5;
protected override float ToScrollbarPosition(double scrollPosition)
{
if (Precision.AlmostEquals(0, ScrollableExtent))
return 0;
return (float)(ScrollbarPaddingTop + (ScrollbarMovementExtent - (ScrollbarPaddingTop + ScrollbarPaddingBottom)) * (scrollPosition / ScrollableExtent));
}
protected override float FromScrollbarPosition(float scrollbarPosition)
{
if (Precision.AlmostEquals(0, ScrollbarMovementExtent))
return 0;
return (float)(ScrollableExtent * ((scrollbarPosition - ScrollbarPaddingTop) / (ScrollbarMovementExtent - (ScrollbarPaddingTop + ScrollbarPaddingBottom))));
}
#endregion
#region Absolute scrolling
private bool absoluteScrolling;
protected override bool IsDragging => base.IsDragging || absoluteScrolling;
public bool OnPressed(KeyBindingPressEvent<GlobalAction> e)
{
switch (e.Action)
{
case GlobalAction.AbsoluteScrollSongList:
beginAbsoluteScrolling(e);
return true;
}
return false;
}
public void OnReleased(KeyBindingReleaseEvent<GlobalAction> e)
{
switch (e.Action)
{
case GlobalAction.AbsoluteScrollSongList:
endAbsoluteScrolling();
break;
}
}
protected override bool OnMouseDown(MouseDownEvent e)
{
if (e.Button == MouseButton.Right)
{
// To avoid conflicts with context menus, disallow absolute scroll if it looks like things will fall over.
if (GetContainingInputManager()!.HoveredDrawables.OfType<IHasContextMenu>().Any())
return false;
beginAbsoluteScrolling(e);
}
return base.OnMouseDown(e);
}
protected override void OnMouseUp(MouseUpEvent e)
{
if (e.Button == MouseButton.Right)
endAbsoluteScrolling();
base.OnMouseUp(e);
}
protected override bool OnMouseMove(MouseMoveEvent e)
{
if (absoluteScrolling)
{
ScrollToAbsolutePosition(e.CurrentState.Mouse.Position);
return true;
}
return base.OnMouseMove(e);
}
private void beginAbsoluteScrolling(UIEvent e)
{
ScrollToAbsolutePosition(e.CurrentState.Mouse.Position);
absoluteScrolling = true;
}
private void endAbsoluteScrolling() => absoluteScrolling = false;
#endregion
}
#endregion
}
}