104 lines
3.2 KiB
C#
104 lines
3.2 KiB
C#
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using System;
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using System.Windows.Forms;
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using System.Runtime.InteropServices;
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using System.Drawing;
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// http://stackoverflow.com/questions/479284/mouse-wheel-event-c
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namespace UserControls
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{
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public class ChildMouseWheelManagedForm : Form, IMessageFilter
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{
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private bool managed;
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public ChildMouseWheelManagedForm()
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: this(true)
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{
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}
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public ChildMouseWheelManagedForm(bool start)
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{
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managed = false;
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if (start)
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ManagedMouseWheelStart();
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}
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protected override void Dispose(bool disposing)
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{
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if (disposing)
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ManagedMouseWheelStop();
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base.Dispose(disposing);
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}
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/************************************
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* IMessageFilter implementation
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* *********************************/
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private const int WM_MOUSEWHEEL = 0x20a;
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// P/Invoke declarations
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[DllImport("user32.dll")]
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private static extern IntPtr WindowFromPoint(Point pt);
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[DllImport("user32.dll")]
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private static extern IntPtr SendMessage(IntPtr hWnd, int msg, IntPtr wp, IntPtr lp);
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private bool IsChild(Control ctrl)
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{
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Control loopCtrl = ctrl;
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while (loopCtrl != null && loopCtrl != this)
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loopCtrl = loopCtrl.Parent;
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return (loopCtrl == this);
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}
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public bool PreFilterMessage(ref Message m)
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{
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if (m.Msg == WM_MOUSEWHEEL)
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{
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//Ensure the message was sent to a child of the current form
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if (IsChild(Control.FromHandle(m.HWnd)))
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//if (this.Contains(Control.FromHandle(m.HWnd)))
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{
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// Find the control at screen position m.LParam
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Point pos = new Point(m.LParam.ToInt32() & 0xffff, m.LParam.ToInt32() >> 16);
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// Is mouse inside the form
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if (pos.X >= this.Left && pos.X <= Left + Width && pos.Y >= Top && pos.Y <= Top+Height)
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{
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//Ensure control under the mouse is valid and is not the target control
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//otherwise we'd be trap in a loop.
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IntPtr hWnd = WindowFromPoint(pos);
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if (hWnd != IntPtr.Zero && hWnd != m.HWnd && Control.FromHandle(hWnd) != null)
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{
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SendMessage(hWnd, m.Msg, m.WParam, m.LParam);
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return true;
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}
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}
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}
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}
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return false;
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}
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/****************************************
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* MouseWheelManagedForm specific methods
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* **************************************/
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public void ManagedMouseWheelStart()
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{
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if (!managed)
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{
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managed = true;
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Application.AddMessageFilter(this);
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}
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}
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public void ManagedMouseWheelStop()
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{
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if (managed)
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{
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managed = false;
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Application.RemoveMessageFilter(this);
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}
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}
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}
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}
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