在前一个Post当中,指出了在WPF的WindowInteropHelper类中的一个BUG:通过WindowInteropHelper的Owner属性不能实现把WPF窗口的Owner属性设置为一个非WPF窗口的句柄。
在我的Post帖出后不到一天,在WPF SDK的Blog上,就针对这个BUG给出了一个非常完美的解决方案。既然不同通过设置WindowStartupLocation.CenterOwner来改变窗口的位置。那么我们就用WindowStartupLocation.Manual来手动计算设置窗口的位置。大致的代码如下:
using System.Windows;
using System.Windows.Interop; // WindowInteropHelper
...
// Instantiate the owned WPF window
Window cw = new Window();
// Set the owned WPF window’s owner with the non-WPF owner window
IntPtr ownerWindowHandle = ...;
// Set the owned WPF window’s owner with the non-WPF owner window
WindowInteropHelper helper = new WindowInteropHelper(cw);
helper.Owner = ownerWindowHandle;
// Manually calculate Top/Left to appear centered
int nonWPFOwnerLeft = ...; // Get non-WPF owner’s Left
int nonWPFOwnerWidth = ...; // Get non-WPF owner’s Width
int nonWPFOwnerTop = ...; // Get non-WPF owner’s Top
int nonWPFOwnerHeight = ...; // Get non-WPF owner’s Height
cw.WindowStartupLocation = WindowStartupLocation.Manual;
cw.Left = nonWPFOwnerLeft + (nonWPFOwnerWidth - cw.Width) / 2;
cw.Top = nonWPFOwnerTop + (nonWPFOwnerHeight - cw.Height) / 2;
// Show the owned WPF window
cw.Show();
这段代码理论上没有什么问题呢?但是WPF是支持设备独立的。因此,在非WPF Owner窗口的某些情况下可能会因为DPI的而不能正常工作。解决这个问题,可以利用HwndSource类进行窗口位置的设备独立计算:
using System.Windows; // Window, WindowStartupLocation, Point
using System.Windows.Interop; // WindowInteropHelper, HwndSource
using System.Windows.Media; // Matrix
...
// Instantiate the owned WPF window
CenteredWindow cw = new CenteredWindow();
// Get the handle to the non-WPF owner window
IntPtr ownerWindowHandle = ...; // Get hWnd for non-WPF window
// Set the owned WPF window’s owner with the non-WPF owner window
WindowInteropHelper helper = new WindowInteropHelper(cw);
helper.Owner = ownerWindowHandle;
// Center window
// Note - Need to use HwndSource to get handle to WPF owned window,
// and the handle only exists when SourceInitialized has been
// raised
cw.SourceInitialized += delegate
{
// Get WPF size and location for non-WPF owner window
int nonWPFOwnerLeft = ...; // Get non-WPF owner’s Left
int nonWPFOwnerWidth = ...; // Get non-WPF owner’s Width
int nonWPFOwnerTop = ...; // Get non-WPF owner’s Top
int nonWPFOwnerHeight = ...; // Get non-WPF owner’s Height
// Get transform matrix to transform non-WPF owner window
// size and location units into device-independent WPF
// size and location units
HwndSource source = HwndSource.FromHwnd(helper.Handle);
if (source == null) return;
Matrix matrix = source.CompositionTarget.TransformFromDevice;
Point ownerWPFSize = matrix.Transform(
new Point(nonWPFOwnerWidth, nonWPFOwnerHeight));
Point ownerWPFPosition = matrix.Transform(
new Point(nonWPFOwnerLeft, nonWPFOwnerTop));
// Center WPF window
cw.WindowStartupLocation = WindowStartupLocation.Manual;
cw.Left = ownerWPFPosition.X + (ownerWPFSize.X - cw.Width) / 2;
cw.Top = ownerWPFPosition.Y + (ownerWPFSize.Y - cw.Height) / 2;
};
// Show WPF owned window
cw.Show();
在上面的代码中需要注意的是HwndSource的使用。这个类需要一个窗口句柄,因此它的代码被放在一个SourceInitialized的事件委派函数中执行。
最后,除了上面这种方法,其实我们还可以用Win32 API函数来实现,在ATL的CWindow类中,就有这样的一个函数,我直接把放在下面,有兴趣的朋友参考其中的实现原理:
...{
ATLASSERT(::IsWindow(m_hWnd));
// determine owner window to center against
DWORD dwStyle = GetStyle();
if(hWndCenter == NULL)
...{
if(dwStyle & WS_CHILD)
hWndCenter = ::GetParent(m_hWnd);
else
hWndCenter = ::GetWindow(m_hWnd, GW_OWNER);
}
// get coordinates of the window relative to its parent
RECT rcDlg;
::GetWindowRect(m_hWnd, &rcDlg);
RECT rcArea;
RECT rcCenter;
HWND hWndParent;
if(!(dwStyle & WS_CHILD))
...{
// don't center against invisible or minimized windows
if(hWndCenter != NULL)
...{
DWORD dwStyleCenter = ::GetWindowLong(hWndCenter, GWL_STYLE);
if(!(dwStyleCenter & WS_VISIBLE) || (dwStyleCenter & WS_MINIMIZE))
hWndCenter = NULL;
}
// center within screen coordinates
::SystemParametersInfo(SPI_GETWORKAREA, NULL, &rcArea, NULL);
if(hWndCenter == NULL)
rcCenter = rcArea;
else
::GetWindowRect(hWndCenter, &rcCenter);
}
else
...{
// center within parent client coordinates
hWndParent = ::GetParent(m_hWnd);
ATLASSERT(::IsWindow(hWndParent));
::GetClientRect(hWndParent, &rcArea);
ATLASSERT(::IsWindow(hWndCenter));
::GetClientRect(hWndCenter, &rcCenter);
::MapWindowPoints(hWndCenter, hWndParent, (POINT*)&rcCenter, 2);
}
int DlgWidth = rcDlg.right - rcDlg.left;
int DlgHeight = rcDlg.bottom - rcDlg.top;
// find dialog's upper left based on rcCenter
int xLeft = (rcCenter.left + rcCenter.right) / 2 - DlgWidth / 2;
int yTop = (rcCenter.top + rcCenter.bottom) / 2 - DlgHeight / 2;
// if the dialog is outside the screen, move it inside
if(xLeft < rcArea.left)
xLeft = rcArea.left;
else if(xLeft + DlgWidth > rcArea.right)
xLeft = rcArea.right - DlgWidth;
if(yTop < rcArea.top)
yTop = rcArea.top;
else if(yTop + DlgHeight > rcArea.bottom)
yTop = rcArea.bottom - DlgHeight;
// map screen coordinates to child coordinates
return ::SetWindowPos(m_hWnd, NULL, xLeft, yTop, -1, -1,
SWP_NOSIZE | SWP_NOZORDER | SWP_NOACTIVATE);
}