我一直在尝试为现有的.Net WinForms控件绘制自定义边框.我试过这个是通过创建一个类来控制我想要改变它的边框颜色,然后在绘画过程中尝试几个东西.我尝试过以下方法：
1.捕获WM_NCPAINT.这有点起作用.下面的代码的问题是,当控件调整大小时,边框将在右侧和底侧被切断.不好.
protected override void WndProc(ref Message m)
{
if (m.Msg == NativeMethods.WM_NCPAINT) {
WmNcPaint(ref m);
return;
}
base.WndProc(ref m);
}
private void WmNcPaint(ref Message m)
{
if (BorderStyle == BorderStyle.None) {
return;
}
IntPtr hDC = NativeMethods.GetWindowDC(m.HWnd);
if (hDC != IntPtr.Zero) {
using (Graphics g = Graphics.FromHdc(hDC)) {
ControlPaint.DrawBorder(g,new Rectangle(0,this.Width,this.Height),_BorderColor,ButtonBorderStyle.Solid);
}
m.Result = (IntPtr)1;
NativeMethods.ReleaseDC(m.HWnd,hDC);
}
}
2.覆盖void OnPaint.这适用于某些控件,但不是全部.这还要求您将BorderStyle设置为BorderStyle.None,并且您必须手动清除paint上的背景,否则调整大小时的you get this.
protected override void OnPaint(PaintEventArgs e)
{
base.OnPaint(e);
ControlPaint.DrawBorder(e.Graphics,ButtonBorderStyle.Solid);
}
3.重写void OnResize和void OnPaint(如方法2中所示).通过这种方式,它可以很好地调整大小,但是当Panel启用了AutoScroll时则不会,在这种情况下,当向下滚动时它将是look like this.如果我尝试使用WM_NCPAINT绘制边框,则Refresh()无效.
protected override void OnResize(EventArgs eventargs)
{
base.OnResize(eventargs);
Refresh();
}
建议非常欢迎.我想知道最好的方法是什么,对于多种类型的控件(我必须为多个默认的WinForms控件执行此操作).
解决方法
编辑：所以我想出了导致我最初问题的原因.经过很长一段时间的修补,试验和查看.Net框架源代码,这里有一个明确的方法(考虑到你有一个控件继承自你想要绘制自定义边框的控件)：
[DllImport("user32.dll")]
public static extern bool RedrawWindow(IntPtr hWnd,IntPtr lprcUpdate,IntPtr hrgnUpdate,RedrawWindowFlags flags);
[Flags()]
public enum RedrawWindowFlags : uint
{
Invalidate = 0X1,InternalPaint = 0X2,Erase = 0X4,Validate = 0X8,NoInternalPaint = 0X10,NoErase = 0X20,NoChildren = 0X40,AllChildren = 0X80,UpdateNow = 0X100,EraseNow = 0X200,Frame = 0X400,NoFrame = 0X800
}
// Make sure that WS_BORDER is a style,otherwise borders aren't painted at all
protected override CreateParams CreateParams
{
get
{
if (DesignMode) {
return base.CreateParams;
}
CreateParams cp = base.CreateParams;
cp.ExStyle &= (~0x00000200); // WS_EX_CLIENTEDGE
cp.Style |= 0x00800000; // WS_BORDER
return cp;
}
}
// During OnResize,call RedrawWindow with Frame|UpdateNow|Invalidate so that the frame is always redrawn accordingly
protected override void OnResize(EventArgs e)
{
base.OnResize(e);
if (DesignMode) {
RecreateHandle();
}
RedrawWindow(this.Handle,IntPtr.Zero,RedrawWindowFlags.Frame | RedrawWindowFlags.UpdateNow | RedrawWindowFlags.Invalidate);
}
// Catch WM_NCPAINT for painting
protected override void WndProc(ref Message m)
{
if (m.Msg == NativeMethods.WM_NCPAINT) {
WmNcPaint(ref m);
return;
}
base.WndProc(ref m);
}
// Paint the custom frame here
private void WmNcPaint(ref Message m)
{
if (BorderStyle == BorderStyle.None) {
return;
}
IntPtr hDC = NativeMethods.GetWindowDC(m.HWnd);
using (Graphics g = Graphics.FromHdc(hDC)) {
g.DrawRectangle(new Pen(_BorderColor),this.Width - 1,this.Height - 1));
}
NativeMethods.ReleaseDC(m.HWnd,hDC);
}
简而言之,保持OnPaint不变,确保设置了WS_BORDER,然后捕获WM_NCPAINT并通过hDC绘制边框,并确保在OnResize中调用RedrawWindow.
这甚至可以扩展以绘制自定义滚动条,因为这是在WM_NCPAINT期间可以绘制的窗口框架的一部分.
我从中删除了我的旧答案.
编辑2：对于ComboBox,你必须在WndProc()中捕获WM_PAINT,因为由于某种原因,用于绘制ComboBox的.Net源不使用OnPaint(),而是使用WM_PAINT.所以像这样：
protected override void WndProc(ref Message m)
{
base.WndProc(ref m);
if (m.Msg == NativeMethods.WM_PAINT) {
OnWmPaint();
}
}
private void OnWmPaint()
{
using (Graphics g = CreateGraphics()) {
if (!_HasBorders) {
g.DrawRectangle(new Pen(BackColor),this.Height - 1));
return;
}
if (!Enabled) {
g.DrawRectangle(new Pen(_BorderColorDisabled),this.Height - 1));
return;
}
if (ContainsFocus) {
g.DrawRectangle(new Pen(_BorderColorActive),this.Height - 1));
return;
}
g.DrawRectangle(new Pen(_BorderColor),this.Height - 1));
}
}
