110 lines
2.6 KiB
C#
110 lines
2.6 KiB
C#
using System.Windows;
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using System.Windows.Controls;
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using System.Windows.Input;
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using System.Windows.Media;
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namespace WxOrder.Framework.Commons
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{
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/// <summary>
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/// 让页面级 ScrollViewer 在鼠标悬停在子控件（如 DataGrid、图表等）上时也能随鼠标滚轮滚动。
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/// 用法：在 ScrollViewer 上设置 common:ScrollViewerBehavior.FixMouseWheel="True"。
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/// </summary>
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public static class ScrollViewerBehavior
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{
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public static readonly DependencyProperty FixMouseWheelProperty =
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DependencyProperty.RegisterAttached(
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"FixMouseWheel",
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typeof(bool),
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typeof(ScrollViewerBehavior),
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new PropertyMetadata(false, OnFixMouseWheelChanged));
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public static bool GetFixMouseWheel(DependencyObject obj)
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=> (bool)obj.GetValue(FixMouseWheelProperty);
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public static void SetFixMouseWheel(DependencyObject obj, bool value)
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=> obj.SetValue(FixMouseWheelProperty, value);
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private static void OnFixMouseWheelChanged(DependencyObject d, DependencyPropertyChangedEventArgs e)
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{
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if (!(d is ScrollViewer scrollViewer))
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{
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return;
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}
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if ((bool)e.NewValue)
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{
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scrollViewer.PreviewMouseWheel += OnPreviewMouseWheel;
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}
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else
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{
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scrollViewer.PreviewMouseWheel -= OnPreviewMouseWheel;
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}
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}
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private static void OnPreviewMouseWheel(object sender, MouseWheelEventArgs e)
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{
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if (e.Handled || !(sender is ScrollViewer scrollViewer) || scrollViewer.ScrollableHeight <= 0)
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{
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return;
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}
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if (!(e.OriginalSource is DependencyObject original))
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{
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return;
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}
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// 从鼠标所在控件向上查找，确认它属于当前 ScrollViewer
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var current = original;
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var inside = false;
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while (current != null)
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{
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if (ReferenceEquals(current, scrollViewer))
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{
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inside = true;
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break;
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}
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// 若鼠标位于一个能自行纵向滚动的内部 ScrollViewer 上（例如下拉列表、
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// 启用了滚动的表格），则交给内部处理，避免抢走它的滚动。
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if (current is ScrollViewer inner &&
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inner.ComputedVerticalScrollBarVisibility == Visibility.Visible &&
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inner.ScrollableHeight > 0)
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{
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return;
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}
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current = VisualTreeHelper.GetParent(current);
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}
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if (!inside)
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{
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return;
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}
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// 按系统默认的滚轮行数滚动当前页面
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var lines = (int)(e.Delta / Mouse.MouseWheelDeltaForOneLine * SystemParameters.WheelScrollLines);
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if (lines == 0)
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{
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lines = e.Delta > 0 ? 1 : -1;
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}
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if (lines < 0)
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{
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for (var i = 0; i < -lines; i++)
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{
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scrollViewer.LineDown();
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}
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}
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else
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{
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for (var i = 0; i < lines; i++)
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{
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scrollViewer.LineUp();
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}
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}
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e.Handled = true;
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}
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}
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}
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