using System.Windows.Media;
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using System.Windows;
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using System.Windows.Threading;
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using System.Windows.Controls;
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namespace SeqEditor.Util
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{
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public class DispatcherHelper
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{
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private static readonly DispatcherOperationCallback exitFrameCallback = ExitFrame;
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/// <summary>
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/// Processes all UI messages currently in the message queue.
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/// </summary>
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public static void WaitForPriority()
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{
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// Create new nested message pump.
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DispatcherFrame nestedFrame = new DispatcherFrame();
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// Dispatch a callback to the current message queue, when getting called,
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// this callback will end the nested message loop.
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// The priority of this callback should be lower than that of event message you want to process.
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DispatcherOperation exitOperation = Dispatcher.CurrentDispatcher.BeginInvoke(
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DispatcherPriority.ApplicationIdle, exitFrameCallback, nestedFrame);
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// pump the nested message loop, the nested message loop will immediately
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// process the messages left inside the message queue.
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Dispatcher.PushFrame(nestedFrame);
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// If the "exitFrame" callback is not finished, abort it.
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if (exitOperation.Status != DispatcherOperationStatus.Completed)
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{
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exitOperation.Abort();
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}
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}
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private static Object ExitFrame(Object state)
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{
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DispatcherFrame frame = state as DispatcherFrame;
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// Exit the nested message loop.
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frame.Continue = false;
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return null;
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}
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public static T FindControl<T>(object obj)
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{
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if (obj == null)
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{
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return default(T);
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}
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if (obj is T target)
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{
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return target;
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}
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return FindControl<T>(VisualTreeHelper.GetParent((DependencyObject)obj));
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}
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public static bool IsElementVisibleInScrollViewer(ScrollViewer scrollViewer, DependencyObject element)
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{
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if (scrollViewer == null || element == null)
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return false;
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// 将 element 转换为 FrameworkElement
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var frameworkElement = element as FrameworkElement;
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if (frameworkElement == null)
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return false;
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try
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{
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// 获取元素相对于 ScrollViewer 的坐标变换
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GeneralTransform transform = frameworkElement.TransformToVisual(scrollViewer);
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// 计算元素在 ScrollViewer 坐标系中的位置和大小
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Rect elementRect = new Rect(
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transform.Transform(new Point(0, 0)),
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transform.Transform(new Point(frameworkElement.ActualWidth, frameworkElement.ActualHeight))
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);
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// ScrollViewer 的视区矩形
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Rect viewportRect = new Rect(
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0,
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0,
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scrollViewer.ViewportWidth,
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scrollViewer.ViewportHeight
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);
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// 检查是否相交（部分可见也算可见）
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//return viewportRect.IntersectsWith(elementRect);
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// 如果需要完全可见，使用以下代码：
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return viewportRect.Contains(elementRect);
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}
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catch (ArgumentException)
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{
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// 如果元素尚未加载或不可见，TransformToVisual 可能抛出异常
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return false;
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}
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}
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/// <summary>
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/// 查找第一个指定类型的子控件
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/// </summary>
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public static T FindVisualChild<T>(DependencyObject parent) where T : DependencyObject
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{
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if (parent == null)
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return null;
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for (int i = 0; i < VisualTreeHelper.GetChildrenCount(parent); i++)
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{
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var child = VisualTreeHelper.GetChild(parent, i);
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// 找到指定类型
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if (child is T t)
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return t;
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// 递归查找
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var result = FindVisualChild<T>(child);
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if (result != null)
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return result;
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}
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return null;
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}
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}
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}
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