MFC Windows 程序设计->控制窗口大小 WM_GETMINMAXINFO

 

A final aspect of Clock that deserves scrutiny is its OnGetMinMaxInfo handler. As a window is being resized, it receives a series of WM_GETMINMAXINFO messages with lParam pointing to a MINMAXINFO structure containing information about the window's minimum and maximum "tracking" sizes. You can limit a window's minimum and maximum sizes programmatically by processing WM_GETMINMAXINFO messages and copying the minimum width and height to the x and y members of the structure's ptMinTrackSize field and the maximum width and height to the x and y members of the ptMaxTrackSize field. Clock prevents its window from being reduced to less than 120 pixels horizontally and vertically with the following OnGetMinMaxInfo handler:

void CMainWindow::OnGetMinMaxInfo (MINMAXINFO* pMMI)
{
    pMMI->ptMinTrackSize.x = 120;
    pMMI->ptMinTrackSize.y = 120;
} 

The tracking dimensions copied to MINMAXINFO are measured in device units, or pixels. In this example, the window's maximum size is unconstrained because pMMI->ptMaxTrackSize is left unchanged. You could limit the maximum window size to one-half the screen size by adding the statements

pMMI->ptMaxTrackSize.x = ::GetSystemMetrics (SM_CXSCREEN) / 2;
pMMI->ptMaxTrackSize.y = ::GetSystemMetrics (SM_CYSCREEN) / 2; 

to the message handler.