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113 lines
3.6 KiB
C#
113 lines
3.6 KiB
C#
// Copyright (c) 2007-2018 ppy Pty Ltd <contact@ppy.sh>.
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// Licensed under the MIT Licence - https://raw.githubusercontent.com/ppy/osu/master/LICENCE
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using System;
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using System.Linq;
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namespace osu.Game.Screens.Select.Carousel
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{
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/// <summary>
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/// A group which ensures at least one child is selected (if the group itself is selected).
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/// </summary>
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public class CarouselGroupEagerSelect : CarouselGroup
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{
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public CarouselGroupEagerSelect()
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{
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State.ValueChanged += v =>
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{
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if (v == CarouselItemState.Selected)
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attemptSelection();
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};
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}
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/// <summary>
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/// The last selected item.
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/// </summary>
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protected CarouselItem LastSelected { get; private set; }
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/// <summary>
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/// We need to keep track of the index for cases where the selection is removed but we want to select a new item based on its old location.
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/// </summary>
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private int lastSelectedIndex;
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/// <summary>
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/// To avoid overhead during filter operations, we don't attempt any selections until after all
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/// children have been filtered. This bool will be true during the base <see cref="Filter(FilterCriteria)"/>
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/// operation.
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/// </summary>
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private bool filteringChildren;
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public override void Filter(FilterCriteria criteria)
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{
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filteringChildren = true;
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base.Filter(criteria);
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filteringChildren = false;
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attemptSelection();
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}
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public override void RemoveChild(CarouselItem i)
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{
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base.RemoveChild(i);
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if (i != LastSelected)
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updateSelectedIndex();
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}
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public override void AddChild(CarouselItem i)
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{
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base.AddChild(i);
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attemptSelection();
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}
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protected override void ChildItemStateChanged(CarouselItem item, CarouselItemState value)
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{
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base.ChildItemStateChanged(item, value);
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switch (value)
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{
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case CarouselItemState.Selected:
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updateSelected(item);
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break;
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case CarouselItemState.NotSelected:
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case CarouselItemState.Collapsed:
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attemptSelection();
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break;
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}
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}
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private void attemptSelection()
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{
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if (filteringChildren) return;
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// we only perform eager selection if we are a currently selected group.
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if (State != CarouselItemState.Selected) return;
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// we only perform eager selection if none of our children are in a selected state already.
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if (Children.Any(i => i.State == CarouselItemState.Selected)) return;
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PerformSelection();
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}
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protected virtual void PerformSelection()
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{
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CarouselItem nextToSelect =
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Children.Skip(lastSelectedIndex).FirstOrDefault(i => !i.Filtered) ??
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Children.Reverse().Skip(InternalChildren.Count - lastSelectedIndex).FirstOrDefault(i => !i.Filtered);
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if (nextToSelect != null)
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nextToSelect.State.Value = CarouselItemState.Selected;
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else
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updateSelected(null);
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}
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private void updateSelected(CarouselItem newSelection)
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{
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LastSelected = newSelection;
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updateSelectedIndex();
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}
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private void updateSelectedIndex() => lastSelectedIndex = LastSelected == null ? 0 : Math.Max(0, InternalChildren.IndexOf(LastSelected));
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}
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}
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