[英]How to set the margin with P/Invoke SendMessage?
这是一个支持RightMargin属性的文本框控件。 在Win7上测试:
using System;
using System.ComponentModel;
using System.Windows.Forms;
using System.Runtime.InteropServices;
class MyTextBox : TextBox {
private int mRightMargin;
[DefaultValue(0)]
public int RightMargin {
get { return mRightMargin; }
set {
if (value < 0) throw new ArgumentOutOfRangeException();
mRightMargin = value;
if (this.IsHandleCreated) updateMargin();
}
}
protected override void OnHandleCreated(EventArgs e) {
base.OnHandleCreated(e);
if (mRightMargin > 0) updateMargin();
}
private void updateMargin() {
// Send EM_SETMARGINS
SendMessage(this.Handle, 0xd3, (IntPtr)2, (IntPtr)(mRightMargin << 16));
}
[DllImport("user32.dll", CharSet = CharSet.Auto)]
private static extern IntPtr SendMessage(IntPtr hWnd, int msg, IntPtr wp, IntPtr lp);
}
根据文件 :
[DllImport("user32.dll", CharSet=CharSet.Auto)]
static extern IntPtr SendMessage(IntPtr hwnd, int msg, IntPtr wParam, IntPtr lParam);
...
SendMessage(hwnd, EM_SETMARGINS, (IntPtr)EC_RIGHTMARGIN, (IntPtr)(rightMargin << 16));
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