不要看到什么就说Bug In most descendants of TWinControl, the job of drawing the control's surface belongs to the underlying Windows screen object. If a control has visible features that cannot be rendered by a Windows screen object, it requires access to a canvas object so it can do its own drawing.TCustomControl is one of two base classes for controls that draw their own surfaces. Because TCustomControl is descended from TWinControl, instances of its descendants can receive the focus and serve as containers.Classes of controls that perform their own screen rendering and do not need the features of TWinControl should be descendants of TGraphicControl instead of TCustomControl. TGraphicControl objects can render themselves with less overhead, because they do not have underlying Windows screen objects.TCustomControl objects have a Paint method, which is called whenever the control needs to render its image. Custom controls paint themselves using the Canvas property.
许多网页都有背景图案，这样可以使页面看起来更加醒目。在Ｄｅｌｐｈｉ 里你也可以设计这种类型的窗体。
在Form中添加Image控件，设BMP图象，name为image1，在Form的OnCreate事件中写入 form1.Brush.Bitmap:=image1.picture.bitmap;form可以
panel1.Brush.Bitmap:=image1.picture.Bitmap;panel1不可以
为什么？
In most descendants of TWinControl, the job of drawing the control's surface belongs to the underlying Windows screen object. If a control has visible features that cannot be rendered by a Windows screen object, it requires access to a canvas object so it can do its own drawing.TCustomControl is one of two base classes for controls that draw their own surfaces. Because TCustomControl is descended from TWinControl, instances of its descendants can receive the focus and serve as containers.Classes of controls that perform their own screen rendering and do not need the features of TWinControl should be descendants of TGraphicControl instead of TCustomControl. TGraphicControl objects can render themselves with less overhead, because they do not have underlying Windows screen objects.TCustomControl objects have a Paint method, which is called whenever the control needs to render its image. Custom controls paint themselves using the Canvas property.