BCB RichEdit添加背景图片

重载RichEdit的WndProc改写WM_ERASEBKGND、CN_CTLCOLORMSGBOX、CN_CTLCOLORSTATIC消息

代码如下：

在Form类中声明

Graphics::TBitmap *bmp;
TWndMethod OldProc;
void __fastcall NewProc(TMessage &message)
{
            if(message.Msg== WM_ERASEBKGND)
             message.Result=1;
             else  if((message.Msg==CN_CTLCOLORMSGBOX)||(message.Msg==CN_CTLCOLORSTATIC)
                      )
             {
               message.Result=NULL_BRUSH; 
             }  
             else 
             OldProc(message);}

在Form构造函数中

替换RichEdit窗口过程，设置扩展透明样式

bmp=new Graphics::TBitmap;
bmp->LoadFromFile("a.bmp");
OldProc=RichEdit1->WindowProc; 
 RichEdit1->WindowProc=NewProc; SetWindowLong(RichEdit1->Handle,   GWL_EXSTYLE,   GetWindowLong(RichEdit1->Handle,GWL_EXSTYLE)  |   WS_EX_TRANSPARENT);
OK,最后在Form的OnPaint中处理背景图片
Canvas->Draw(0,0,bmp);