我从评论中提到的“RenderDemo” Frankenapps 中获取了“LineBoundsDemoControl”,作为回答我的问题的答案。
实际绘制发生在“drawingContext”的“Render”方法中。它看起来非常像带有笔和刷子的 GDI+。
如果您像我一样是 Avalonia/xaml 的新手,则具有“AffectsRender”的静态构造函数可能会让人感到奇怪。根据 Avalonia 源代码,此方法表示属性更改应导致控件失效(重新绘制)。不断学习...
此方法应在控件的静态构造函数中调用,其中包含每个在更改时应导致重新绘制的控件属性。这类似于 WPF 的 FrameworkPropertyMetadata.AffectsRender 标志。
using System;
using Avalonia;
using Avalonia.Controls;
using Avalonia.Media;
using Avalonia.Rendering.SceneGraph;
using Avalonia.Threading;
namespace RenderDemo.Controls
{
public class LineBoundsDemoControl : Control
{
static LineBoundsDemoControl()
{
AffectsRender<LineBoundsDemoControl>(AngleProperty);
}
public LineBoundsDemoControl()
{
var timer = new DispatcherTimer();
timer.Interval = TimeSpan.FromSeconds(1 / 60.0);
timer.Tick += (sender, e) => Angle += Math.PI / 360;
timer.Start();
}
public static readonly StyledProperty<double> AngleProperty =
AvaloniaProperty.Register<LineBoundsDemoControl, double>(nameof(Angle));
public double Angle
{
get => GetValue(AngleProperty);
set => SetValue(AngleProperty, value);
}
public override void Render(DrawingContext drawingContext)
{
var lineLength = Math.Sqrt((100 * 100) + (100 * 100));
var diffX = LineBoundsHelper.CalculateAdjSide(Angle, lineLength);
var diffY = LineBoundsHelper.CalculateOppSide(Angle, lineLength);
var p1 = new Point(200, 200);
var p2 = new Point(p1.X + diffX, p1.Y + diffY);
var pen = new Pen(Brushes.Green, 20, lineCap: PenLineCap.Square);
var boundPen = new Pen(Brushes.Black);
drawingContext.DrawLine(pen, p1, p2);
drawingContext.DrawRectangle(boundPen, LineBoundsHelper.CalculateBounds(p1, p2, pen));
}
}
}