Not a member of Pastebin yet?
Sign Up,
it unlocks many cool features!
- // Copyright (c) The Avalonia Project. All rights reserved.
- // Licensed under the MIT license. See licence.md file in the project root for full license information.
- using System;
- using System.Collections.Generic;
- using System.Linq;
- using Avalonia.Logging;
- using Avalonia.Threading;
- namespace Avalonia.Layout
- {
- /// <summary>
- /// Manages measuring and arranging of controls.
- /// </summary>
- public class LayoutManager : ILayoutManager
- {
- private Queue<ILayoutable> _toMeasure = new Queue<ILayoutable>();
- private Queue<ILayoutable> _toArrange = new Queue<ILayoutable>();
- private bool _queued;
- private bool _running;
- /// <summary>
- /// Gets the layout manager.
- /// </summary>
- public static ILayoutManager Instance => AvaloniaLocator.Current.GetService<ILayoutManager>();
- /// <inheritdoc/>
- public void InvalidateMeasure(ILayoutable control)
- {
- Contract.Requires<ArgumentNullException>(control != null);
- Dispatcher.UIThread.VerifyAccess();
- if (!control.IsAttachedToVisualTree)
- {
- #if DEBUG
- throw new AvaloniaInternalException(
- "LayoutManager.InvalidateMeasure called on a control that is detached from the visual tree.");
- #else
- return;
- #endif
- }
- _toMeasure.Enqueue(control);
- _toArrange.Enqueue(control);
- QueueLayoutPass();
- }
- /// <inheritdoc/>
- public void InvalidateArrange(ILayoutable control)
- {
- Contract.Requires<ArgumentNullException>(control != null);
- Dispatcher.UIThread.VerifyAccess();
- if (!control.IsAttachedToVisualTree)
- {
- #if DEBUG
- throw new AvaloniaInternalException(
- "LayoutManager.InvalidateArrange called on a control that is detached from the visual tree.");
- #else
- return;
- #endif
- }
- _toArrange.Enqueue(control);
- QueueLayoutPass();
- }
- /// <inheritdoc/>
- public void ExecuteLayoutPass()
- {
- const int MaxPasses = 3;
- Dispatcher.UIThread.VerifyAccess();
- if (!_running)
- {
- _running = true;
- Logger.Information(
- LogArea.Layout,
- this,
- "Started layout pass. To measure: {Measure} To arrange: {Arrange}",
- _toMeasure.Count,
- _toArrange.Count);
- var stopwatch = new System.Diagnostics.Stopwatch();
- stopwatch.Start();
- try
- {
- for (var pass = 0; pass < MaxPasses; ++pass)
- {
- var toMeasure = _toMeasure;
- var toArrange = _toArrange;
- _toMeasure = new Queue<ILayoutable>();
- _toArrange = new Queue<ILayoutable>();
- ExecuteMeasurePass(toMeasure);
- ExecuteArrangePass(toArrange);
- if (_toMeasure.Count == 0)
- {
- break;
- }
- }
- }
- finally
- {
- _running = false;
- }
- stopwatch.Stop();
- Logger.Information(LogArea.Layout, this, "Layout pass finised in {Time}", stopwatch.Elapsed);
- }
- _queued = false;
- }
- /// <inheritdoc/>
- public void ExecuteInitialLayoutPass(ILayoutRoot root)
- {
- Measure(root);
- Arrange(root);
- // Running the initial layout pass may have caused some control to be invalidated
- // so run a full layout pass now (this usually due to scrollbars; its not known
- // whether they will need to be shown until the layout pass has run and if the
- // first guess was incorrect the layout will need to be updated).
- ExecuteLayoutPass();
- }
- private void ExecuteMeasurePass(Queue<ILayoutable> toMeasure)
- {
- while (toMeasure.Count > 0)
- {
- var control = toMeasure.Dequeue();
- if (!control.IsMeasureValid && control.IsAttachedToVisualTree)
- {
- Measure(control);
- }
- }
- }
- private void ExecuteArrangePass(Queue<ILayoutable> toArrange)
- {
- while (toArrange.Count > 0)
- {
- var control = toArrange.Dequeue();
- if (!control.IsArrangeValid && control.IsAttachedToVisualTree)
- {
- Arrange(control);
- }
- }
- }
- private void Measure(ILayoutable control)
- {
- // Controls closest to the visual root need to be arranged first. We don't try to store
- // ordered invalidation lists, instead we traverse the tree upwards, measuring the
- // controls closest to the root first. This has been shown by benchmarks to be the
- // fastest and most memory-efficent algorithm.
- if (control.VisualParent is ILayoutable parent)
- {
- Measure(parent);
- }
- // If the control being measured has IsMeasureValid == true here then its measure was
- // handed by an ancestor and can be ignored. The measure may have also caused the
- // control to be removed.
- if (!control.IsMeasureValid && control.IsAttachedToVisualTree)
- {
- if (control is ILayoutRoot root)
- {
- root.Measure(Size.Infinity);
- }
- else
- {
- control.Measure(control.PreviousMeasure.Value);
- }
- }
- }
- private void Arrange(ILayoutable control)
- {
- if (control.VisualParent is ILayoutable parent)
- {
- Arrange(parent);
- }
- if (!control.IsArrangeValid && control.IsAttachedToVisualTree)
- {
- if (control is IEmbeddedLayoutRoot embeddedRoot)
- control.Arrange(new Rect(embeddedRoot.AllocatedSize));
- else if (control is ILayoutRoot root)
- control.Arrange(new Rect(root.DesiredSize));
- else if (control.PreviousArrange != null)
- {
- // Has been observed that PreviousArrange sometimes is null, probably a bug somewhere else.
- // Condition observed: control.VisualParent is Scrollbar, control is Border.
- control.Arrange(control.PreviousArrange.Value);
- }
- }
- }
- private void QueueLayoutPass()
- {
- if (!_queued && !_running)
- {
- Dispatcher.UIThread.InvokeAsync(ExecuteLayoutPass, DispatcherPriority.Layout);
- _queued = true;
- }
- }
- }
- }
Add Comment
Please, Sign In to add comment