为什么使用SetWindowRgn函数后窗口样式变化很大？

[赤勇玄心行天道]

没有使用SetWindowRgn函数时：


已经使用SetWindowRgn函数后：


可以看出来窗口样式变化很大，边框变得特别粗，样式也变成了经典windows样式，关键是我还发现窗口的大小有变大了一点点，这是为什么呢？有什么办法可以避免呢？

代码如下：

	hWnd2 = CreateWindowExW(0, szWindowClass, szTitle, WS_OVERLAPPEDWINDOW, 100, 100, 500, 500, nullptr, nullptr, hInstance, nullptr);

	hRgn = CreateRoundRectRgn(0, 0, 500, 500, 50, 50);
	SetWindowRgn(hWnd2, hRgn, FALSE );
	CloseHandle(hRgn);
	
	ShowWindow(hWnd2, nCmdShow);
	UpdateWindow(hWnd2);

[schlafenhamster]

After a successful call to SetWindowRgn, the operating system owns the region specified by the region handle hRgn. The operating system does not make a copy of the region, so do not make any further function calls with this region handle, and do not close this region handle.

[schlafenhamster]

例子
void CTransDlgDlg::OnButton1()
{
// TODO: Add your control notification handler code here
static BOOL sw=FALSE;
if(!sw)
{
sw=TRUE;
CRect rcWin;
GetWindowRect(&rcWin);
//
CRect rcClt;
GetClientRect(&rcClt);
// rcClt.DeflateRect(20,20);
ClientToScreen(rcClt);
rcClt.OffsetRect(-rcWin.left,-rcWin.top);
//
int offX=rcClt.left;
int offY=rcClt.top;
rcWin.OffsetRect(-rcWin.left,-rcWin.top);
//
CRgn tmp;
tmp.CreateRectRgnIndirect(&rcClt);
// client - ctrls
RgnSubtractCtrls(tmp,offX,offY);
// finally
CRgn rgn;
rgn.CreateRectRgnIndirect(&rcWin);
rgn.CombineRgn(&rgn,&tmp,RGN_DIFF);
DeleteObject(tmp);
//
SetWindowRgn(rgn,TRUE);
m_Trans.SetWindowText("不透明");
}
else
{
sw=FALSE;
SetWindowRgn(0,TRUE);
m_Trans.SetWindowText("透明");
}
}

[赤勇玄心行天道]

引用 1 楼 schlafenhamster 的回复:

After a successful call to SetWindowRgn, the operating system owns the region specified by the region handle hRgn. The operating system does not make a copy of the region, so do not make any further function calls with this region handle, and do not close this region handle.

我注释掉了CloseHandle也是一样的

[schlafenhamster]

参考
void CAboutDlg::OnOK()
{
// TODO: Add extra validation here
int R=50;// 2R=100
HRGN hRgn = CreateRoundRectRgn(0, 0, 460, 200, R, R);
MoveWindow(CRect(100, 100, 460+2*R, 200+2*R),TRUE);// 窗口大 2R ！！！
SetWindowRgn(hRgn,TRUE);//
// CDialog::OnOK();
}
注意 窗口 大小 与 rgn 大小

[schlafenhamster]

是不是 aero 主题 引起 ？

[蒋晟]

设置窗口区域会禁用视觉风格 https://docs.microsoft.com/zh-cn/windows/desktop/Controls/cookbook-overview#ignore_top_level 可以用UpdateLayeredWindow做局部透明。参考https://docs.microsoft.com/en-us/previous-versions/ms997507(v=msdn.10)