普通的窗体都是方形的，使用API函数可以打破传统，做出各种奇怪形状的窗体，这里只研究圆角窗体。先来理解一个重要的概念区域。区域是描述设备场景中某一块的GDI对象，每个区域都有一个句柄。一个区域可以是矩形，也可以是复杂的多边形，甚至是几个区域组织

普通的窗体都是方形的，使用API函数可以打破传统，做出各种奇怪形状的窗体，这里只研究圆角窗体。

    先来理解一个重要的概念→“区域”。区域是描述设备场景中某一块的GDI对象，每个区域都有一个句柄。一个区域可以是矩形，也可以是复杂的多边形，甚至是几个区域组织在一起。窗体默认的区域就是我们看到的矩形，当然它并非一定要用这个默认的区域。

    现在开始，新建VB工程，把默认窗体"Form1"的"BorderStyle"属性设置为[0 - None]。

   

源代码如下：

Option Explicit

Private Declare Function CreateRectRgn Lib "gdi32" (ByVal X1 As Long, _

    ByVal Y1 As Long, _

    ByVal X2 As Long, _

    ByVal Y2 As Long) As Long

Private Declare Function CreateRoundRectRgn Lib "gdi32" (ByVal X1 As Long, _

    ByVal Y1 As Long, _

    ByVal X2 As Long, _

    ByVal Y2 As Long, _

    ByVal X3 As Long, _

    ByVal Y3 As Long) As Long

Private Declare Function CombineRgn Lib "gdi32" (ByVal hDestRgn As Long, _

    ByVal hSrcRgn1 As Long, _

    ByVal hSrcRgn2 As Long, _

    ByVal nCombineMode As Long) As Long

Private Declare Function SetWindowRgn Lib "user32" (ByVal hWnd As Long, _

    ByVal hRgn As Long, _

    ByVal bRedraw As Boolean) As Long

Private Declare Function DeleteObject Lib "gdi32" (ByVal hObject As Long) As Long

Private Const RGN_AND = 1

Private MyRgn1 As Long

Private MyRgn2 As Long

Private MyRgn As Long   '保存圆角区域，也是窗体最终的形状

Private Sub Form_Click()

    Unload Me

End Sub

Private Sub Form_Load()

    Dim w As Long, h As Long

    w = ScaleX(Me.Width, vbTwips, vbPixels)

    h = ScaleY(Me.Height, vbTwips, vbPixels)

'----｛下面为十五种圆角窗体代码，任选一种即可实现相应的效果｝----

'01.左上圆其余直

'   MyRgn = CreateRoundRectRgn(30, 30, w + 30, h + 30, 16, 16)

'02.左下圆其余直

'   MyRgn = CreateRoundRectRgn(30, -30, w + 30, h - 30, 16, 16)

'03.右上圆其余直

'   MyRgn = CreateRoundRectRgn(-30, 30, w - 30, h + 30, 16, 16)

'04.右下圆其余直

'   MyRgn = CreateRoundRectRgn(-30, -30, w - 30, h - 30, 16, 16)

'05.上圆下直

'   MyRgn = CreateRoundRectRgn(30, 30, w - 30, h + 30, 16, 16)

'06.上直下圆

'   MyRgn = CreateRoundRectRgn(30, -30, w - 30, h - 30, 16, 16)

'07.左圆右直

'   MyRgn = CreateRoundRectRgn(30, 30, w + 30, h - 30, 16, 16)

'08.左直右圆

'   MyRgn = CreateRoundRectRgn(-30, 30, w - 30, h - 30, 16, 16)

'09.左上右下圆左下右上直

'   MyRgn = CreateRectRgn(0, 0, 0, 0)

'   MyRgn1 = CreateRoundRectRgn(30, 30, w + 30, h + 30, 16, 16)

'   MyRgn2 = CreateRoundRectRgn(-30, -30, w - 30, h - 30, 16, 16)

'   Call CombineRgn(MyRgn, MyRgn1, MyRgn2, RGN_AND)

'10.左下右上圆左上右下直

'   MyRgn = CreateRectRgn(0, 0, 0, 0)

'   MyRgn1 = CreateRoundRectRgn(-30, 30, w - 30, h + 30, 16, 16)

'   MyRgn2 = CreateRoundRectRgn(30, -30, w + 30, h - 30, 16, 16)

'   Call CombineRgn(MyRgn, MyRgn1, MyRgn2, RGN_AND)

'11.左上直其余圆

'   MyRgn = CreateRectRgn(0, 0, 0, 0)

'   MyRgn1 = CreateRoundRectRgn(30, -30, w - 30, h - 30, 16, 16)

'   MyRgn2 = CreateRoundRectRgn(-30, 30, w - 30, h + 30, 16, 16)

'   Call CombineRgn(MyRgn, MyRgn1, MyRgn2, RGN_AND)

'12.左下直其余圆

'   MyRgn = CreateRectRgn(0, 0, 0, 0)

'   MyRgn1 = CreateRoundRectRgn(30, 30, w - 30, h + 30, 16, 16)

'   MyRgn2 = CreateRoundRectRgn(-30, -30, w - 30, h - 30, 16, 16)

'   Call CombineRgn(MyRgn, MyRgn1, MyRgn2, RGN_AND)

'13.右上直其余圆

'   MyRgn = CreateRectRgn(0, 0, 0, 0)

'   MyRgn1 = CreateRoundRectRgn(30, -30, w - 30, h - 30, 16, 16)

'   MyRgn2 = CreateRoundRectRgn(30, 30, w + 30, h + 30, 16, 16)

'   Call CombineRgn(MyRgn, MyRgn1, MyRgn2, RGN_AND)

'14.右下直其余圆

'   MyRgn = CreateRectRgn(0, 0, 0, 0)

'   MyRgn1 = CreateRoundRectRgn(30, 30, w - 30, h + 30, 16, 16)

'   MyRgn2 = CreateRoundRectRgn(30, -30, w + 30, h - 30, 16, 16)

'   Call CombineRgn(MyRgn, MyRgn1, MyRgn2, RGN_AND)

'15.四角都为圆角

'   MyRgn = CreateRoundRectRgn(30, 30, w - 30, h - 30, 16, 16)

'--------------------------------------------------------------------------------------

    Call SetWindowRgn(Me.hWnd, MyRgn, True) '改变窗口的区域为"MyRgn"

    Me.BackColor = QBColor(5)

End Sub

Private Sub Form_Unload(Cancel As Integer)

    '删除非空区域

    If MyRgn <> 0 Then DeleteObject MyRgn

    If MyRgn1 <> 0 Then DeleteObject MyRgn1

    If MyRgn2 <> 0 Then DeleteObject MyRgn2

End Sub

 

以上为引用原文：http://www.pczpg.com/html/bianchengkaifa/VB/20091128/24014.html